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 paper, a cost-effective and high-accuracy precoding technique based on ϵ-Fuzzy pareto active learning (FPAL) is proposed for millimeter wave (mmWave) massive MIMO communications. The proposed method achieves a low iteration convergence with low complexity. Two practical structures, namely fully-connected and partially-connected structures are considered for hybrid precoding. Furthermore, the effect of high and low-resolution quantization in the digital-to-analog converter, phase shifter, and imperfect channel state information are discussed. The performance results of the proposed technique and alternating minimization methods beside fully digital techniques are compared and... 

It is well-known that the behavior of soil-structure systems can be well described using a limited number of nondimensional parameters. This is the outcome of researches based on the premise that the foundation is bonded to the ground. Here, it is shown the concept can be extended to systems with foundation uplift. A set of non-dimensional parameters are introduced which controls the main features of uplifting systems. The effect of foundation uplift on response of soil-structure systems are investigated parametrically through time history analysis for a wide range of systems subjected to ground motions recorded on different soil types. In particular, the effects of uplift on displacement... 

This study was a prototype segmentation of Iran's inbound tourism market with a concentration on culture. The focus of this paper was to introduce a step by step description of the methodology used to segment Iran's inbound tourism market. In the first phase, cluster analysis was employed to segment the entire market based on two dimensions of tourists' expenditure and cultural traits. In the second phase, the resulting clusters were divided into further subgroups using a common sense approach. Additional variables were utilised to profile the segments, and finally, the segmentation process was verified through outcome analysis  

In most of researches on soil-structure systems, it is assumed that the foundation is bonded to the ground where no foundation uplift is allowed. Uplifting makes changes in force–displacement behavior of the soil-structure systems, which in turn alters structural demands. In this research, a set of non-dimensional parameters is considered which controls the behavior of uplifting systems. The effects of foundation uplift on response of soil-structure system are investigated parametrically through time history analysis for a wide range of systems subjected to harmonic excitation and also ground motions recorded on soft soil with predominant period. It is seen that the response of systems with... 

Recently, the traditional strength-based design (SBD) philosophy is being replaced by more relevant displacement-based design (DBD) approach. As a main step, DBD method requires a simplified procedure to estimate the inelastic displacement demands of the structure. This step is usually done by either replacing the non-linear system by an equivalent linear system or employing the well-known concepts of inelastic design spectra. The application of different DBD procedures and their deficiencies, thus, have been the subject of numerous researches during the recent years. However, the effect of soil is usually ignored. On the other hand, it is well-known that soil affects the structural behavior... 

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... 

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... 

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 paper, we evaluate the capacity of Multiple-Input Multiple-Output (MIMO) systems using directional antennas in non-isotropic scattering environments. Our analytical analysis approach results in closed-form approximate formulas in low Signal to Noise Ratio (SNR) regime (in contrast to previous research works which have investigated the same problem by employing experimental or simulation frameworks). We propose an upper bound for the introduced approximate error. Our results show that MIMO systems equipped with directional antennas may have much higher capacity in nonisotropic scattering environments compared to MIMO systems equipped with omni-directional antennas. We also evaluate... 

This paper addresses dynamic cell formation problem (DCFP) which has been explored vastly for several years. Although a considerable body of literature in this filed, two remarkable aspects have been significantly ignored so far, as uncertainty and human-related issues. In order to compensate such a shortage, this paper develops a bi-objective stochastic model. The first objective function of the developed model seeks to minimize total cost of machine procurement, machine relocation, inter-cell moves, overtime utilization, worker hiring/laying-off, and worker moves between cells; while the second objective function maximizes labor utilization of the cellular manufacturing system. In the... 

In this paper, trace locality of reference (LoR) is identified as a mechanism to predict the behavior of a variety of systems. If two objects were accessed nearby in the past and the first one is accessed again, trace LoR predicts that the second one will be accessed in near future. To capture trace LoR, trace graph is introduced. Although trace LoR can be observed in a variety of systems, but the focus of this paper is to characterize it for data accesses in memory management systems. In this field, it is compared with recency-based prediction (LRU stack) and it is shown that not only the model is much simpler, but also it outperforms recency-based prediction in all cases. The paper... 

It is now known that at least 10% of samples with pancreatic cancers (PC) contain a causative mutation in the known susceptibility genes, suggesting the importance of identifying cancer-associated genes that carry the causative mutations in high-risk individuals for early detection of PC. In this study, we develop a statistical pipeline using a new concept, called gene-motif, that utilizes both mutated genes and mutational processes to identify 4211 3-nucleotide PC-associated gene-motifs within 203 significantly mutated genes in PC. Using these gene-motifs as distinguishable features for pancreatic cancer subtyping results in identifying five PC subtypes with distinguishable phenotypes and... 

This paper has been prepared, based on reports regarding extraordinary induced ac voltage on buried gas pipelines in residential and industrial areas of the capital city of Tehran, especially in densely populated central areas. Also, some reports are considered on the existence of ac induced voltage in buried gas pipelines under the overhead transmission lines, for example, one case located 80 Km to the west of Tehran, in an agricultural region of the town of Abyek. In this paper, the results of an extensive theoretical, experimental and practical investigation and implementation of methods carried out during the last two years are introduced. Furthermore, this paper includes evaluation of... 

The axial turbine is one of the most challenging components of gas turbines for industrial and aerospace applications. With the ever-increasing requirement for high-aerodynamic performance blades, three-dimensional aerodynamic shape optimization is of great importance. In this research, the rear part of a gas turbine consisting of a one-stage axial turbine is optimized numerically. A useful optimization algorithm is presented to improve the efficiency and/or pressure ratio of the axial turbine with two different objective functions. The three-dimensional blade-shape optimization is employed to study the effects of the turbine stator and rotor lean and sweep angles on the turbine performance.... 

A high quality joint of zinc based pressure die cast alloys can be hardly achieved by conventional fusion welding. In this study, a novel technique to achieve the globular weld structure using stirring the localized semisolid zone during butt joining of Zamak-3 pressure die cast alloy is proposed and effect of welding parameters on mechanical and microstructural properties are investigated. A gas heating system was designed to heat up the nitrogen gas to desired temperature accurately to create a localized semisolid pool. At this stage a fine stirrer was introduced into the weld seam in order to mix the two sides into a single uniform joint. By presented process, globular microstructure of...