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maleki--hesam
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Dynamic modeling and sensitivity analysis of atomic force microscope pushing force in nanoparticle manipulation on a rough substrate [electronic resource]
, Article Journal of Advanced Science, Engineering and Medicine ; 2013, Vol. 5, pp. 1-10 ; Mahboobi, Seyed Hanif ; Meghdari, Ali ; Sharif University of Technology
Abstract
An Atomic Force Microscope (AFM) is a capable tool to manipulate nanoparticles by exerting pushing force on the nanoparticles located on the substrate. In reality, the substrate cannot be considered as a smooth surface particularly at the nanoscale. Hence, the particle may encounter a step on the substrate during a manipulation. In this study, dynamics of the nanoparticle on a stepped substrate and critical pushing force in the manipulation are investigated. There are two possible dynamic modes that may happen in the manipulation on the stepped substrate. In one mode, the nanoparticle may slide on the step edge and then climb up to the step which is a desired mode. Another possible mode is...
Classification of vascular function in upper limb using bilateral photoplethysmographic signals
, Article Physiological Measurement ; Volume 29, Issue 3 , 2008 , Pages 365-374 ; 09673334 (ISSN) ; Zahedi, E ; Jajai, H. M ; Sharif University of Technology
2008
Abstract
Bilateral PPG signals have been used for comparative study of two groups of healthy (free from any cardiovascular risk factors) and diabetic (as cardiovascular disease risk group) subjects in the age-matched range 40-50 years. The peripheral blood pulsations were recorded simultaneously from right and left index fingers for 90 s. Pulses have been modeled with the ARX440 model in the interval of 300 sample points with 100 sample points overlap between segments. Model parameters of three segments based on the highest fitness (higher than 80%) of modeled segments were retained for each subject. Subsequently, principal component analysis (PCA) was applied to the parameters of retained segments...
VoIP users’ Quality of Experience (QoE)Evaluation
, Ph.D. Dissertation Sharif University of Technology ; Jahangir, Amir Hossein (Supervisor)
Abstract
Quality of Experience (QoE) indicates the overall quality of one service such as Voice over IP (VoIP) from users' point of view by considering several systems, human, and contextual factors. QoE measurement and prediction are more challenging than Quality of Service (QoS) which is only related to network parameters. There exist various objective and subjective methods for QoE prediction. This research investigates various features affecting QoE by proposing a comprehensive subjective evaluation by employing a large number of users. We show that many unconsidered factors including speaker specifications and signal properties, such as signal-to-noise ratio (SNR), can affect QoE so that the SNR...
Toward a comprehensive subjective evaluation of VoIP users’ quality of experience (QoE): a case study on Persian language
, Article Multimedia Tools and Applications ; Volume 80, Issue 21-23 , 2021 , Pages 31783-31802 ; 13807501 (ISSN) ; Jahangir, A. H ; Hosseini, S. M ; Sharif University of Technology
Springer
2021
Abstract
Quality of Experience (QoE) measures the overall quality of a service from users’ point of view by considering several system, human, and contextual factors. There exist various objective and subjective methods for QoE prediction. Although the subjective approach is more expensive and challenging than the objective approach, QoE’s level can be more accurately determined by a subjective test. This paper investigates various features affecting QoE by proposing a comprehensive subjective evaluation. First, we show that many unconsidered factors can significantly affect QoE. We have generated voice samples featuring different values for novel factors related to the speaker, signal, and network....
Speed limit of quantum metrology
, Article Scientific Reports ; Volume 13, Issue 1 , 2023 ; 20452322 (ISSN) ; Ahansaz, B ; Maleki, A ; Sharif University of Technology
Nature Research
2023
Abstract
Quantum metrology employs nonclassical systems to improve the sensitivity of measurements. The ultimate limit of this sensitivity is dictated by the quantum Cramér–Rao bound. On the other hand, the quantum speed limit bounds the speed of dynamics of any quantum process. We show that the speed limit of quantum dynamics sets a fundamental bound on the minimum attainable phase estimation error through the quantum Cramér–Rao bound, relating the precision directly to the underlying dynamics of the system. In particular, various metrologically important states are considered, and their dynamical speeds are analyzed. We find that the bound could, in fact, be related to the nonclassicality of...
Prediction of Rolling Element Bearings Degradation Trend Using Limited Data
, M.Sc. Thesis Sharif University of Technology ; Behzad, Mehdi (Supervisor) ; Arghand, Hesam Al-din (Co-Supervisor)
Abstract
Condition monitoring of machinery is of significant economic importance to mitigate production losses resulting from downtimes. Unforeseen failure of roller element bearings is the most common issue observed in industrial units. However, detecting and tracking the progression of these failures through machine vibration monitoring and predicting the deterioration of these rotating components are viable solutions. Numerous studies have focused on using laboratory accelerated life test data for fault detection and remaining useful life prediction of these components. While online monitoring of all equipment in the industry may not be feasible, and conditions in the field differ from laboratory...
Intelligent Fault Diagnosis using Multiple Sensor Data Fusion for Detecting Misalignment and Unbalance
, M.Sc. Thesis Sharif University of Technology ; Behzad, Mehdi (Supervisor) ; Arghand, Hesam Al-Din (Co-Supervisor)
Abstract
Intelligent predictive maintenance is recognized as a cornerstone of Industry 4.0, where intelligent software is employed for the early detection of faults and the prevention of unexpected failures. Recent research indicates that the integration of multi-sensor data for fault diagnosis of gearboxes and bearings, using artificial intelligence models, has been successful. However, conventional methods face several challenges. These include an over-reliance on the signal characteristics of a single sensor and the impracticality of applying intelligent learning methods, particularly deep learning, despite their high potential, due to the unavailability of sufficiently large and diverse...
A novel enzyme based biosensor for catechol detection in water samples using artificial neural network
, Article Biochemical Engineering Journal ; Volume 128 , 2017 , Pages 1-11 ; 1369703X (ISSN) ; Kashanian, S ; Maleki, E ; Nazari, M ; Sharif University of Technology
Elsevier B.V
2017
Abstract
Biosensors could be used as digital devices to measure the sample infield. Consequently, computational programming along with experimental achievements are required. In this study, a novel biosensor/artificial neural network (ANN) integrated system was developed. Poly (3,4-ethylenedioxy-thiophene)(PEDOT), graphene oxide nano-sheets (GONs) and laccase (Lac) were used to construct a biosensor. The simple and one-pot process was accomplished by electropolymerizing 3,4-ethylenedioxy-thiophene (EDOT) along with GONs and Lac as dopants on glassy carbon electrode. Scanning electron microscopy (SEM) and electrochemical characterization were conducted to confirm successful enzyme entrapment. The...
Modeling of severe shot peening effects to obtain nanocrystalline surface on cast iron using artificial neural network
, Article Materials Today: Proceedings ; Volume 3, Issue 6 , 2016 , Pages 2197-2206 ; 22147853 (ISSN) ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Severe plastic deformation methods such as severe shot peening are used in order to improve mechanical properties of the components by surface microstructure nanocrystallization. Severe shot peening is one of the popular mechanical surface treatments generally aimed at generating nanograined layer and compressive residual stress close to the surface. Moreover, artificial neural network has been used as an efficient approach to predict and optimize the engineering problems. In present study effects of conventional and severe shot peening on cast iron were modelled by means of artificial neural networks and they were compared. The obtained results indicate that severe shot peening has superior...
Evaluation of Response Modification Factor for Cable Styaed Bridges
, M.Sc. Thesis Sharif University of Technology ; Maleki, Shervin (Supervisor)
Abstract
Bridges are among the crucial elements of transportation networks and play an important role in facilitating emergency relief efforts following earthquakes. For this reasons, they should have an appropriate performance in earthquakes; Thus, presentation of true design of bridges was necessary. Elastic design of bridges due to the earthquake is uneconomic; hence, during an earthquake, the codes permitted to structures go to their inelastic behavior domain but inelastic analysis of structures are noncommercial and the capability of detail modeling of the inelastic behavior of the material is still impossible. Therefore, designers use response modification factor to consider the inelastic...
Infilled-pipe damper
, Article Journal of Constructional Steel Research ; Volume 98 , July , 2014 , Pages 45-58 ; ISSN: 0143974X ; Mahjoubi, S ; Sharif University of Technology
2014
Abstract
This paper introduces a new passive control device for protecting structures against earthquakes. The device consists of two welded pipes which have two smaller pipes inside them and the spaces between the pipes are filled with metals such as lead or zinc. The device is loaded in shear and takes advantage of plastification of the outer pipes, the inner pipes and the infilled metals, and the friction between metals as energy absorption mechanisms. Quasi-static cyclic tests are performed on six specimens all showing stable hystereses and high damping. A finite element model is developed and calibrated against test results. The model is used to find the optimum sizes of pipes needed for a...
Seat width requirement for skewed bridges under seismic loads
, Article Scientia Iranica ; Vol. 21, issue. 5 , 2014 , pp. 1471-1479 ; ISSN: 10263098 ; Bagheri, S ; Sharif University of Technology
2014
Abstract
In this paper, the dynamic characteristics of skewed bridges are explored analytically. Closed form solutions for translational and torsional periods of free vibration and mode shapes are given for slab-girder skewed bridges. Moreover, the seismic displacement of the deck of skewed bridges is calculated using the response spectrum method and its skew term is compared with the requirement of AASHTO. The effects of seismic force resisting elements, such as elastomeric bearings and end diaphragms are included. It is shown that the skew term in AASHTO's equation can underestimate the seat width requirement for some bridges. A new skew term for the bridge seat width requirement is suggested
Numerical study of Slotted-Web-Reduced-Flange moment connection
, Article Journal of Constructional Steel Research ; Volume 69, Issue 1 , February , 2012 , Pages 1-7 ; 0143974X (ISSN) ; Tabbakhha, M ; Sharif University of Technology
2012
Abstract
Reduced Beam Section (RBS) and Slotted Beam Web (SBW) are two types of seismic resistant moment connections that were introduced after the 1994 Northridge earthquake. These connections have been tested under cyclic loading and have had acceptable performance. In this paper, a new hybrid connection is introduced that is composed of RBS and SBW and is named Slotted-Web-Reduced- Flange (SWRF). Nonlinear finite element analyses are performed on SWRF under cyclic loading. It is shown that the new connection in some cases performs better than its RBS and SBW predecessors. The effects of panel zone strength, continuity plates and slot length are also investigated
Dual-pipe damper
, Article Journal of Constructional Steel Research ; Volume 85 , 2013 , Pages 81-91 ; 0143974X (ISSN) ; Mahjoubi, S ; Sharif University of Technology
2013
Abstract
In this paper, a new passive earthquake energy dissipative device, called the dual-pipe damper (DPD), is introduced, tested and analytically studied. The device consists of two pipes welded at selected locations and loaded in shear. The inelastic cyclic deformation dissipates energy mainly through flexure of the pipe body. However, at large displacements a tension diagonal forms in the middle of the device which further adds to stiffness and strength. The strength, stiffness and energy dissipation of the DPD is more than two single pipe dampers that were previously studied. Cyclic quasi-static tests were performed on four samples of DPD. Excellent ductility, energy absorption and stable...
Artificial neural network modeling of Pt/C cathode degradation in pem fuel cells
, Article Journal of Electronic Materials ; Volume 45, Issue 8 , 2016 , Pages 3822-3834 ; 03615235 (ISSN) ; Maleki, N ; Sharif University of Technology
Springer New York LLC
2016
Abstract
Use of computational modeling with a few experiments is considered useful to obtain the best possible result for a final product, without performing expensive and time-consuming experiments. Proton exchange membrane fuel cells (PEMFCs) can produce clean electricity, but still require further study. An oxygen reduction reaction (ORR) takes place at the cathode, and carbon-supported platinum (Pt/C) is commonly used as an electrocatalyst. The harsh conditions during PEMFC operation result in Pt/C degradation. Observation of changes in the Pt/C layer under operating conditions provides a tool to study the lifetime of PEMFCs and overcome durability issues. Recently, artificial neural networks...
Pipe damper, Part I: Experimental and analytical study
, Article Journal of Constructional Steel Research ; Volume 66, Issue 8-9 , 2010 , Pages 1088-1095 ; 0143974X (ISSN) ; Bagheri, S ; Sharif University of Technology
2010
Abstract
In this paper the behavior of steel pipes, filled and unfilled with concrete, is studied under cyclic shear to examine the possibility of their use as a seismic damper. Two specimens of steel pipes filled inside with concrete are tested under monotonic and cyclic shear. Four other specimens ofbare steel pipes are tested under fully reversed cyclic shear loading. The results show that the bare steel pipes are capable of absorbing a great amount of energy under a severe cyclic shear loading with a stable hysteretic behavior. This behavior is also simulated using the finite element method. Then, parametric studies are performed to investigate the effects of variations in geometrical properties...
Pipe damper, Part II: Application to bridges
, Article Journal of Constructional Steel Research ; Volume 66, Issue 8-9 , 2010 , Pages 1096-1106 ; 0143974X (ISSN) ; Bagheri, S ; Sharif University of Technology
2010
Abstract
Theoretical and experimental verification of the pipe damper was investigated in Part I of the two companion papers. In this paper, the application of the pipe damper to structures is examined. In particular, single span slab-girder bridges are considered for analytical investigations. A practical detail for the installation of the pipe damper is introduced. Nonlinear dynamic time history analyses are conducted on bridges equipped with the pipe damper and the results are compared with ordinary bridges. Bridge span, ground motion and the pipe length are varied in the analyses. Results show that the pipe damper is a reliable and economical metallic-yielding device that can easily be installed...
A new approach for estimating the seismic soil pressure on retaining walls
, Article Scientia Iranica ; Volume 17, Issue 4 A , Aug , 2010 , Pages 273-284 ; 10263098 (ISSN) ; Mahjoubi, S ; Sharif University of Technology
2010
Abstract
In this paper, a simple finite element model for seismic analysis of retaining walls is introduced. The model incorporates nonlinearity in the behavior of near wall soil, wall flexibility and elastic free field soil response. This model can be employed in nonlinear modeling of retaining walls and bridge abutments. The advantages of this model are simplicity and flexibility in addition to acceptable precision. Using this finite element model, an analytical study is conducted on several soil-wall systems using nonlinear time-history analysis by applying real earthquake records. Based on the results of these analyses, new seismic soil pressure distributions are proposed for different soil and...
Numerical study of external flow over ducts with various cross-sections
, Article Defect and Diffusion Forum ; Volume 366 , 2016 , Pages 10-16 ; 10120386 (ISSN) ; Sadrhosseini, H ; Sharif University of Technology
Trans Tech Publications Ltd
2016
Abstract
In this article a comprehensive numerical study is performed to compare the effect of fluid flow across a duct with various cross sectional shapes and with different velocities of the flow. Circular, elliptical and rectangular cross sections have been chosen for the ducts and air flows across them with four values of low Reynolds numbers in the range of Re = 1 to Re = 1000. Continuity and momentum equations with proper boundary conditions are solved in two dimensions. Streamlines, pressure distribution and Velocity profiles are obtained and creation of vortices, boundary layers, separation region, wake region, reattachment point and stagnation points are studied in detail and the results are...
Modeling of shot-peening effects on the surface properties of a (Tib + Tic)/Ti-6Al-4V composite employing artificial neural networks
, Article Materiali in Tehnologije ; Volume 50, Issue 6 , 2016 , Pages 851-860 ; 15802949 (ISSN) ; Zabihollah, A ; Sharif University of Technology
Institute of Metals Technology
2016
Abstract
Titanium matrix composites (TMCs) have wide application prospects in the field of aerospace, automobile and other industries because of their good properties, such as high specific strength, good ductility, and excellent fatigue properties. However, in order to improve their fatigue strength and life, crack initiation and growth at the surface layers must be suppressed using surface treatments. Shot peening (SP) is an effective surface mechanical treatment method widely used in industry which can improve the mechanical properties of a surface. However, artificial neural networks (ANNs) have been used as an efficient approach to predict and optimize the science and engineering problems. In...