Sharif Digital Repository

In this article, we proposed an active learning method for the direction-of-arrival (DOA) estimation based on uniform linear array (ULA) antennas with very low computational complexity. In particular, an adaptive fuzzy sampling strategy was used to make a model and refine it according to the snapshot data collected by multiple antennas to estimate the DOA angles. The proposed gridless fuzzy pipeline sequential design zero-forcing (PLSD-ZF) sampling can reduce complexity by dividing the angle space into subsets and using the measurements of the appropriate subsets to obtain more accurate DOA estimates. Our simulation and experiment results demonstrate that the proposed fuzzy PLSD-ZF scheme... 

In this article, a novel microstrip antenna for the new industrial, scientific, and medical (ISM) band (24-25 GHz) with a flexible substrate is proposed. This antenna has a small dimension, high gain, and large bandwidth (BW) in the ISM band. Several tests such as bending tests and gas environment tests are performed to show the potential of the antenna in body area networks' (BANs) applications. The design procedure starts with a simple monopole antenna with a simple ground plane. Then, to change the effective permittivity of the substrate, an array of half circles is subtracted from the ground plane. To avoid increasing the dimension of the antenna, a triangular part and a shunt are added... 

In this article, a dual-band sixth order double symmetric T-slot filter is proposed for the 5G communication systems. This filter contains two duplicate square resonators and a T-shape feedline on the Rogers RT duroid 5880 substrate. Operating at the 28 and 38.5 GHz frequencies from licensed 5G frequency bands and small size make this filter appropriate for different 5G applications. Furthermore, an LC equivalent circuit for the filter has been considered that helps us to have a better sight of this filter. Measurement results show good agreement with simulations. The attenuation on the passband is less than 1 dB. In order to evaluate the filter performance besides other millimeter waves... 

In this article, a compact, wideband Yagi-Uda antenna and its phased array antenna is optimized by a multi-objective antenna for the millimeter-wave (mmWave) band of fifth generation (5G) communication systems. Ten geometrical parameters of a single Yagi-Uda antenna are selected to widen the 5G operating bandwidth (BW) and increase the gain together using the Kriging model builder and pipeline sequential design (PLSD) in combined sampling strategy. The single antenna element provides a wide impedance bandwidth (IBW) from 26 to 34 GHz with 20% and a peak measured gain of 5.5 dBi at frequency 28 GHz. The optimized antenna provides a high growth of 27.7% and a 2 dB increase in peak gain over... 

The main purpose of this paper is to present a novel procedure for accelerating a multi-objective optimization method of designing a 5G antenna. The optimization method was chosen after comparing four learning optimization algorithms. The Kriging algorithm was found to be superior to the Artificial Neural Network (ANN), Support Vector Machine (SVM), and Rational algorithms. Our methodology is creatively correlated to exploit some cost functions of height, the Dielectric constant of the substrate, and meta-material design variables, with a view to reducing the return loss and increasing the gain in learning from the Kriging model builder techniques. This was fully achieved in the present... 

In this paper, a reconfigurable patch antenna with Circular Polarization (CP) diversity with theoretical discussion and verification is proposed for fifth generation (5G) of mobile communication systems. The proposed antenna contains two PIN diodes, which are correctly placed on the ground plane to obtain polarization diversity. By switching between two ON/OFF modes in the PIN diodes, the proposed antenna can support either the RHCP mode or the LHCP mode. An antenna with the well-matched impedance bandwidths (S11 ≤ −10 dB) of 2.5 GHz (27 ∼ 29.5 GHz) and 3 GHz (36 ∼ 39 GHz) and the dual-band 3-dB axial ratios of 6% (27.3–29 GHz) and 8.4% (35–38.2 GHz) operates in both the RHCP and LHCP modes.... 

In this article, a 5G compact millimeter-wave dipole antenna with high gain and its array filter-antenna is proposed, following a theoretical discussion is proposed. To increase the gain and focused mainbeam, the double dipole is inserted at the ground plane. The results show that the proposed antenna has an impedance band-width (IBW) of around 7.14% and 6.7 dBi gain at 28 GHz. Next, a 5G filter is proposed with 4% IBW and lower than 0.6 dB gain insertion loss. A simple phase-shifter with 2-bit structure is designed in an 8-elemens array filter-antenna with 0.35 spacing between the two elements which uses a meander-line to reduce mutual-coupling. First, the phased-array filtenna... 

In the present research, the authors have attempted to examine the compressive strength of conventional concrete, which is made using different aggregate sizes and geometries considering various curing temperatures. To this end, different aggregate geometries (rounded and angular) were utilized in various aggregate sizes (10, 20, and 30 mm) to prepare 108 rectangular cubic specimens. Then, the curing process was carried out in the vicinity of wind at different temperatures (5◦ C < T < 30◦ C). Next, the static compression experiments were performed on 28-day concrete specimens. Additionally, each test was repeated three times to check the repeatability of the results. Finally, the mean... 

Purpose: The purpose of this paper is to estimate the wage difference between overeducated and adequately educated workers in a sample of semi-skilled and low-skill occupations in Iran’s labor market. The objective is to see if overeducated employees in these occupations enjoy higher wages in comparison to their adequately educated co-workers. Design/methodology/approach: The authors use the propensity score matching (PSM) model to estimate the wage difference between overeducated and adequately educated workers in a sample of semi-skilled and low-skill occupations in Iran’s labor market. The PSM method allows the authors to prevent selection bias by comparing each group of overeducated... 

Master curves of asphalt binders and mixtures have been traditionally used to evaluate their rheological behavior in the linear viscoelastic range. Different analytical models are available to describe the master curves of bituminous binders and mixtures. No models are currently considered universal for all modeling purposes. In this research, the general structure and capabilities of some of the most commonly used analytical models were investigated. Then, based on the patterns of phase angle master curves of ten neat and modified asphalt binders, four groups of master curve shapes were defined. The goodness of fit of the models for the different groups of master curves was used to develop... 

Solid slugs tracking in melt in the casting is very important. In this study a model for particle transport trajectories is presented. In this model an explicit method was used to evaluate the position of the particles. Comparison between results of present work and other models has good agreement sand this model can expect determining the location of solid particles in the melt. This model is applied to SUTCAST software  

Fabrication of scaffolds with enhanced mechanical properties and desirable cellular compatibility is critical for numerous tissue engineering applications. This study was aimed at fabrication and characterization of a nanofiber skin substitute composed of collagen (Col)/sodium alginate (SA)/ polyethylene oxide (PEO)/Rhodotorula mucilaginosa sp. GUMS16 produced exopolysaccharides (EPS) were prepared using the biaxial electrospinning technique. This study used collagen extracted from the bovine tendon as a natural scaffold, sodium alginate as an absorber of excess wound fluids, and GUMS16 produced exopolysaccharides as an antioxidant. Collagen was characterized using FTIR and EDS analyses. The... 

This paper presents an approach that integrates clinical methods with Neuro-Fuzzy system in order to diagnose Neonatal Jaundice in newborns. First, a fuzzy logic system designed with medical rules to model the uncertainty that exists in medical diagnosis. Then a fuzzy neural network with an evolutionary learning helps the system to learn the new data gained from the patient and to help the fuzzy system to update itself in an online manner. By combining the aforementioned systems, the proposed approach can help physicians to diagnose jaundice with low risk cost associated with this disease. © 2006 IEEE  

Mechanized tunneling method using Tunnel Boring Machine (TBM) is being extensively employed in urban areas, especially when excavation takes place underneath the groundwater table. In this study, three-dimensional coupled Finite Element Analyses (FEA) have been performed to investigate the interaction mechanism between mechanized twin tunnels construction of Shiraz metro (line 2) and groundwater. Firstly, two soil constitutive models (Mohr-Coulomb and Modified Cam-Clay model) of Shiraz lean clay are validated against drained triaxial compression test data. Varying the permeability of the grout layer within the specified range, the base numerical model is then calibrated by the field data of... 

A new strategy for radiation loss reduction in curved slab waveguides is presented. The proposed strategy is based on the proper modification of the boundary conditions at the core-to-cladding interface, whereupon extremely thin conductive nanolayers with non-zero surface conductance are imposed. The obtained numerical results show a noticeable decrease in the overall loss level. © 2008 The Institution of Engineering and Technology  

Circular slab waveguides are conformally transformed into straight inhomogeneous waveguides, where-upon electromagnetic fields in the core are expanded in terms of Legendre polynomial basis functions. Thereafter, different analytical expression of electromagnetic fields in the cladding region, viz. Wentzel-Kramers-Brillouin solution, modified Airy function expansion, and the exact field solution for circular waveguides, i.e., Hankel function of complex order, are each matched to the polynomial expansion of the transverse electric field within the guide. This field matching process renders different boundary conditions to be satisfied by the set of orthogonal Legendre polynomial basis... 

Modification of orthopedic implant surfaces through advanced nanoscale coating methods has made a major breakthrough in maximizing implantation success. Adjustable drug release and biocompatibility are among the most momentous features since they can significantly prevent the implantation failure. In this study, the potential of silk fibroin (SF) nanofibers fabricated via electrospinning, along with titanium oxide nanotube arrays (TNTs) formed through anodization, were exploited to produce a cyto-biocompatible, well-controlled drug delivery system. Highly-ordered TNTs were formed in an organic electrolyte solution within 2 h at the voltage of 60 V under temperature controlling (16 °C).... 

A new method for the robust estimation of target orientation using measured radar cross section is proposed. The method is based on a Generalized Regression Neural Network (GRNN) scheme. The network is trained by the FFT modulus of bistatic radar cross section data sampled at the receiver positions. The target value to be trained is the angle between a defined target orientation and the incident wave. Results based on actual measurements are presented  

We present a new method for the robust estimation of a two-dimensional conducting target orientation using measured radar cross-section data. The method is based on a Generalized Regression Neural Network (GRNN) scheme, which belongs to the family of radial basis neural networks  

In this paper, an unsteady, two-dimensional solver is developed, based on Van Leer's flux splitting algorithm, in conjunction with the "Monotonic Upstream Scheme for Conservation Laws (MUSCL)" limiters for improving the order of accuracy. For a minimum usage of computer memory and faster convergence, the two-layer Baldwin-Lomax turbulence model is implemented for a viscous solution. Three test cases are prepared to validate the solver. The computed results are compared with experimental data and the good agreement of the compared results validates the solver. Finally, the solver is used for the flow through a multi-blade stage of an axial compressor in its design condition. The solutions of...