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A novel algorithm in a linear phased array system for side lobe and grating lobe level reduction with large element spacing
, Article Analog Integrated Circuits and Signal Processing ; Volume 104, Issue 3 , 13 March , 2020 , Pages 265-275 ; Ranjbar, J ; Karami, P ; Sharif University of Technology
Springer
2020
Abstract
Phased array antennas are generally used for the inherent flexibility to beamforming and null-steering electronically. In the phased arrays the side lobes level (SLL) level is main problem which causes waste of energy or saturation of the receiver in the case of presence of the strong spatial blockers. In this paper, a weighting method was first used to reduce the level of SLL. However, this method increased the beam width and reduced resolution, which is not suitable for track applications. In next step hoping to increase the resolution, the distance between the antennas increased. But in this way, grating lobes appeared in the final beam. In fact, the main idea of the article is to solve...
Development and verification of a model to describe an immobilized glucose isomerase packed bed bioreactor
, Article Biochemical Engineering Journal ; Volume 40, Issue 2 , 2008 , Pages 328-336 ; 1369703X (ISSN) ; Roostaazad, R ; Sharif University of Technology
2008
Abstract
In this paper, the performance of immobilized packed bed glucose isomerase enzyme was mathematically modeled. A modified Michaelis-Menten type relation was used to describe the enzyme kinetics. Mass transfer inside the biocatalyst particle and through the bed column was analyzed simultaneously. Using measured data, physicochemical properties including diffusivity, viscosity and density of sugar solutions were correlated with its concentrations and were used to provide precision in solving the set of model equations. Model equations were solved using the Runge-Kutta and Gauss-Seidel algorithms and finite difference numerical method in MATLAB environment. Model output was used to demonstrate...
Binary classification of imbalanced datasets: The case of CoIL challenge 2000
, Article Expert Systems with Applications ; Volume 128 , 2019 , Pages 169-186 ; 09574174 (ISSN) ; Akhavan Niaki, S. T ; Khedmati, M ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This paper presents some approaches based on data mining techniques to solve the prediction task of Computational Intelligence and Learning (CoIL) Challenge 2000. The prediction task of the contest is a direct mailing problem and the goal is to improve its response rate. The main issue in this competition is the incompatibility of the dataset in which the distribution of the classes of the target attribute is highly unbalanced. This in turn causes high error rate in identifying the minority class samples. Three different level methods including data-level, algorithm-level, and hybrid method are used to overcome this issue. The specificity, sensitivity, precision-recall, and ROC criteria are...
Correlation-augmented Naïve Bayes (CAN) Algorithm: A Novel Bayesian Method Adjusted for Direct Marketing
, Article Applied Artificial Intelligence ; 2021 ; 08839514 (ISSN) ; Khedmati, M ; Akhavan Niaki, S. T ; Sharif University of Technology
Taylor and Francis Ltd
2021
Abstract
Direct marketing identifies customers who buy, more probable, a specific product to reduce the cost and increase the response rate of a marketing campaign. The advancement of technology in the current era makes the data collection process easy. Hence, a large number of customer data can be stored in companies where they can be employed to solve the direct marketing problem. In this paper, a novel Bayesian method titled correlation-augment naïve Bayes (CAN) is proposed to improve the conventional naïve Bayes (NB) classifier. The performance of the proposed method in terms of the response rate is evaluated and compared to several well-known Bayesian networks and other well-known classifiers...
Using Data Mining in Customer Relationship Management (Case Study of the Insurance Industry)
, M.Sc. Thesis Sharif University of Technology ; Akhavan Niaki, Taghi (Supervisor) ; Khedmati, Majid (Co-Supervisor)
Abstract
This paper presents some approaches based on data mining techniques to solve the prediction task of Computational Intelligence and Learning (CoIL) Challenge 2000. The prediction task of the contest is a direct mailing problem and the goal is to improve its response rate. The main issue in this competition is the incompatibility of the dataset in which the distribution of the classes of the target attribute is highly unbalanced. This in turn causes high error rate in identifying the minority class samples. Three different level methods including data-level, algorithm-level, and hybrid method are used to overcome this issue. The specificity and sensitivity criteria are employed to compare the...
Functional compartmentalization in the hemocoel of insects
, Article Scientific Reports ; Volume 9, Issue 1 , 2019 ; 20452322 (ISSN) ; Aviles, J ; Adjerid, K ; Schoenewald, C ; Socha, J. J ; Sharif University of Technology
Nature Publishing Group
2019
Abstract
The insect circulatory system contains an open hemocoel, in which the mechanism of hemolymph flow control is ambiguous. As a continuous fluidic structure, this cavity should exhibit pressure changes that propagate quickly. Narrow-waisted insects create sustained pressure differences across segments, but their constricted waist provides an evident mechanism for compartmentalization. Insects with no obvious constrictions between segments may be capable of functionally compartmentalizing the body, which could explain complex hemolymph flows. Here, we test the hypothesis of functional compartmentalization by measuring pressures in a beetle and recording abdominal movements. We found that the...
Linear index coding via graph homomorphism
, Article Proceedings - 2014 International Conference on Control, Decision and Information Technologies, CoDIT 2014 ; 2014 , pp. 158-163 ; ISBN: 9781479967735 ; Siavoshani, M. J ; Sharif University of Technology
2014
Abstract
In [1], [2] it is shown that the minimum broadcast rate of a linear index code over a finite field Fq is equal to an algebraic invariant of the underlying digraph, called minrankq. In [3], it is proved that for F2 and any positive integer k, minrankq(G) ≤ k if and only if there exists a homomorphism from the complement of the graph G to the complement of a particular undirected graph family called 'graph family {Gk}'. As observed in [2], by combining these two results one can relate the linear index coding problem of undirected graphs to the graph homomorphism problem. In [4], a direct connection between linear index coding problem and graph homomorphism problem is introduced. In contrast to...
Emerging OCDMA communication systems and data networks [electronic resource]
, Article Journal of Optical Networking ; Volume 6, Issue 9, 1 September 2007, Pages 1138-1178 ; Sharif University Of Technology
Abstract
I present an in-depth review of the trends and the directions taken by researchers worldwide in optical code-division multiple-access (OCDMA) systems. I highlight those trends and features that I believe are essential to the successful introduction of various OCDMA techniques in communication systems and data networks in the near future. In particular I begin by giving a comprehensive review of the construction of optical orthogonal codes (OOCs). Specifically I discuss the recently developed algorithms that are based on matrix algebra, which simplify and enhance the efficiencies of algorithms in OOC generation. In communication systems studies I first focus on and discuss various OCDMA...
Network delay analysis of a (σ, ρ) - Regular traffic stream over multiple paths in a network of fair-queuing servers
, Article 2013 Iran Workshop on Communication and Information Theory ; May , 2013 , Page(s): 1 - 6 ; 9781467350235 (ISBN) ; Golestani, S. J ; Sharif University of Technology
2013
Abstract
In this paper, we analyze the worst-case delay performance of a network of fair queuing servers in case of multiple-paths between source-destination pairs. In order to develop worst-case delay analysis for the multiple-path scenario, two challenging events should be addressed: merging different sub-streams of a session as well as distributing a traffic stream among different paths (traffic partitioning). Specifically, we propose to merge incoming sub-streams of a session to a node according to a limited rate Fair Queuing (FQ) scheme. Although the merged stream is treated as a unity, this approach results in a guaranteed level of service to each sub-stream. In addition, an algorithm is...
Effects of tool rake angle and tool nose radius on surface quality of ultraprecision diamond-turned porous silicon
, Article Journal of Manufacturing Processes ; Volume 37 , 2019 , Pages 321-331 ; 15266125 (ISSN) ; Akbari, J ; Yan, J ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This paper presents an investigation of the effects of tool rake angle and nose radius on the surface quality of ultraprecision diamond-turned porous silicon. The results showed that as rake angle decreases, the high-stress field induced by the tool edge increases, causing microcracks to propagate extensively near the pore walls. As a result, the ductile-machined areas shrank under a negative tool rake angle. On the other hand, brittle fracture occurred around pores released cutting pressure significantly. These trends of rake angle effects are distinctly different from those in the cutting of non-porous silicon. Finite element simulation of stress in the cutting area agreed with the...
Effects of tool rake angle and tool nose radius on surface quality of ultraprecision diamond-turned porous silicon
, Article Journal of Manufacturing Processes ; Volume 37 , 2019 , Pages 321-331 ; 15266125 (ISSN) ; Akbari, J ; Yan, J ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
This paper presents an investigation of the effects of tool rake angle and nose radius on the surface quality of ultraprecision diamond-turned porous silicon. The results showed that as rake angle decreases, the high-stress field induced by the tool edge increases, causing microcracks to propagate extensively near the pore walls. As a result, the ductile-machined areas shrank under a negative tool rake angle. On the other hand, brittle fracture occurred around pores released cutting pressure significantly. These trends of rake angle effects are distinctly different from those in the cutting of non-porous silicon. Finite element simulation of stress in the cutting area agreed with the...
Precipitate strengthening of pyramidal slip in Mg–Zn alloys
, Article Materials Science and Engineering A ; Volume 804 , 2021 ; 09215093 (ISSN) ; Wang, J ; LLorca, J ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The mechanical properties of Mg-4wt.% Zn alloy single crystals along the [0001] orientation were measured through micropillar compression at 23 °C and 100 °C. Basal slip was dominant in the solution treated alloy, while pyramidal slip occurred in the precipitation hardened alloy. Pyramidal dislocations pass the precipitates by forming Orowan loops, leading to homogeneous deformation and to a strong hardening. The predictions of the yield stress based on the Orowan model were in reasonable agreement with the experimental data. The presence of rod-shape precipitates perpendicular to the basal plane leads to a strong reduction in the plastic anisotropy of Mg. © 2020 Elsevier B.V
Precipitate strengthening of pyramidal slip in Mg–Zn alloys
, Article Materials Science and Engineering A ; Volume 804 , 2021 ; 09215093 (ISSN) ; Wang, J ; LLorca, J ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The mechanical properties of Mg-4wt.% Zn alloy single crystals along the [0001] orientation were measured through micropillar compression at 23 °C and 100 °C. Basal slip was dominant in the solution treated alloy, while pyramidal slip occurred in the precipitation hardened alloy. Pyramidal dislocations pass the precipitates by forming Orowan loops, leading to homogeneous deformation and to a strong hardening. The predictions of the yield stress based on the Orowan model were in reasonable agreement with the experimental data. The presence of rod-shape precipitates perpendicular to the basal plane leads to a strong reduction in the plastic anisotropy of Mg. © 2020 Elsevier B.V
Comparative study on the microstructures and properties of wire+arc additively manufactured 5356 aluminium alloy with argon and nitrogen as the shielding gas
, Article Additive Manufacturing ; Volume 34 , August , 2020 ; Zhang, L. J ; Ning, J ; Wang, X ; Zhang, G. F ; Zhang, J. X ; Na, S. J ; Fatemeh, B ; Sharif University of Technology
Elsevier B. V
2020
Abstract
This research explored the influences of shielding gases on the appearance of weld beads and the microstructures and mechanical properties of thin-wall samples using conventional gas metal arc welding as the heat source by using 5356 aluminium alloy welding wire as the raw materials and nitrogen (N2) and argon (Ar) as the shielding gases. The results showed that under the same parameters and after mono-layer single-bead welding was performed using N2 as the shielding gas, the bead height was higher, the bead width was narrower, and the penetration depth was shallower. The grain size of the thin-wall sample protected by N2 was 43.5–47.8 % smaller than that obtained under Ar protection....
Solid products characterization in a multi-step mineralization process
, Article Chemical Engineering Journal ; Vol. 252 , 2014 , Pages 210-219 ; ISSN: 13858947 ; Shayegan, J ; Sharratt, P ; Yeo, T. Y ; Bu, J
2014
Abstract
In this paper, we describe a carbon dioxide mineralization process and its associated solid products. These solid products include amorphous silica, iron hydroxides and magnesium carbonates. These products were subjected to various characterization tests, and the results are published here. It was found that the iron hydroxides from this process can have different crystalline properties, and their formation depended very much on the pH of the reaction conditions. Different forms of magnesium carbonate were also obtained, and the type of carbonate precipitated was found to be dependent on the carbonation temperature. Hydromagnesite was obtained mainly at low temperatures, while dypingite was...
Experimental and numerical investigation of pulse-shaped split Hopkinson pressure bar test
, Article Materials Science and Engineering A ; Volume 539 , 2012 , Pages 285-293 ; 09215093 (ISSN) ; Ashrafi, M. J ; Arghavani, J ; Sharif University of Technology
2012
Abstract
Employing a proper pulse shaper in the conventional split Hopkinson pressure bar (SHPB) test helps to achieve dynamic equilibrium condition and to fulfill a constant strain rate condition in the test specimen. To this end, the parameters affecting the incident pulse shape, i.e., pulse shaper thickness, pulse shaper diameter, striker bar length and striker bar velocity are experimentally studied. Moreover, simulation results, validated by experimental data together with wave propagation analysis, are exploited to provide general guidelines to properly design a pulse shaper. It is recommended to use a relatively large diameter pulse shaper for testing work-hardening materials. Also, for...
Investigating and modeling the cleaning-in-place process for retrieving the membrane permeate flux: Case study of hydrophilic polyethersulfone (PES)
, Article Journal of the Taiwan Institute of Chemical Engineers ; Volume 62 , May , 2016 , Pages 150–157 ; 18761070 (ISSN) ; Shayegan, J ; Sargolzaei, J ; Sharif University of Technology
Taiwan Institute of Chemical Engineers
2016
Abstract
In this work the effects of backwash pressure, duration of acid and sodium hydroxide backwashing, sodium hydroxide concentration, and the duration of forward washing on performance of permeate flux recovery (PFR) were investigated. A two-level fractional factorial design (FFD) was used to design the experiments. The ability of back propagation neural network (BPNN) and radial basis function neural network (RBFNN) in predicting the performance of cleaning-in-place (CIP) of hydrophilic polyethersulfone (PES) membrane were investigated. It is found that BPNN has better ability in predicting the PFR performance than RBFNN. The best architecture of BPNN was a network consisting of 1 hidden layer...
Development of DESHIMA: A redshift machine based on a superconducting on-chip filterbank
, Article Proceedings of SPIE - The International Society for Optical Engineering ; Volume 8452 , 2012 ; 0277786X (ISSN) ; 9780819491534 (ISBN) ; Baselmans, J. J. A ; Van Der Werf, P. P ; Knoors, B ; Javadzadeh, S. M. H ; Yates, S. J. C ; Thoen, D. J ; Ferrari, L ; Baryshev, A. M ; Lankwarden, Y. J. Y ; De Visser, P. J ; Janssen, R. M. J ; Klapwijk, T. M ; Sharif University of Technology
2012
Abstract
Distant, dusty and extremely luminous galaxies form a key component of the high redshift universe, tracing the period of intense cosmic activity that ultimately gave rise to the present-day universe. These highly luminous galaxies, first detected in the ground-based submillimeter region, are however optically very faint, which hampers identification of the optical counterpart and the measurement of a redshift. We are developing a new direct-detection submm spectrograph DESHIMA. By taking advantage of the rapidly advancing technology of superconducting microresonators, DESHIMA will revolutionize the appearance and capabilities of a submm spectrograph. There will no longer be large grating...
Organic compound characterization and source apportionment of indoor and outdoor quasi-ultrafine particulate matter in retirement homes of the Los Angeles Basin
, Article Indoor Air ; Volume 20, Issue 1 , 2010 , Pages 17-30 ; 09056947 (ISSN) ; Minguillón, M. C ; Polidori, A ; Schauer, J. J ; Delfino, R. J ; Sioutas, C ; Sharif University of Technology
2010
Abstract
Quasi-ultrafine (quasi-UF) particulate matter (PM0.25) and its components were measured in indoor and outdoor environments at four retirement communities in Los Angeles Basin, California, as part of the Cardiovascular Health and Air Pollution Study (CHAPS). The present paper focuses on the characterization of the sources, organic constituents and indoor and outdoor relationships of quasi-UF PM. The average indoor/outdoor ratios of most of the measured polycyclic aromatic hydrocarbons (PAHs), hopanes, and steranes were close to or slightly lower than 1, and the corresponding indoor-outdoor correlation coefficients (R) were always positive and, for the most part, moderately strong (median R...
Sensitive spectrophotometric detection of dopamine, levodopa and adrenaline using surface plasmon resonance band of silver nanoparticles
, Article Journal of the Iranian Chemical Society ; Volume 7, Issue SUPPL. 1 , 2010 , Pages S83-S91 ; 1735207X (ISSN) ; Tashkhourian, J ; Khodaveisi, J ; Sharif University of Technology
2010
Abstract
A simple and effective procedure is proposed for spectrophotometric determination of catecholamines; Dopamine (1), L-Dopa (2) and Adrenaline (3). It was found that the reduction of Ag+ to silver nanoparticles (Ag-NPs) by these catecholamines in the presence of polyvinylpyrrolidone (PVP) as a stabilizing agent produced very intense surface plasmon resonance peak of Ag-NPs. The plasmon absorbance of the Ag-NPs allows the quantitative spectrophotometric detection of the catecholamines. The calibration curves derived from the changes in absorbance at λ = 440 nm were linear with concentration of Dopamine, Levodopa and Adrenaline in the range of 3.2×10-6- 2.0x10-5 M, 1.6x10-7 - 1.0×10-5 M,...