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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...
The characteristics of serrated flow in superalloy IN738LC
, Article Materials Science and Engineering A ; Volume 486, Issue 1-2 , 2008 , Pages 376-380 ; 09215093 (ISSN) ; Asgari, S ; Sharif University of Technology
2008
Abstract
Serrated flow was investigated in superalloy IN738LC, a nickel-base γ′ age-hardened alloy. In this material serrated flow appeared between 350 and 450 °C and strain rate of (8.77 × 10-5 to 8.77 × 10-3) s-1. Activation energy for this process was calculated to be 0.69-0.86 eV which is in good agreement with the values reported for similar alloys. Results show that the diffusion rate of substitutional solute atoms at this temperature range is too low to cause this effect. This suggests that the interaction of solute atoms and moving dislocation is responsible for the observed serrated flow in this alloy. © 2007 Elsevier B.V. All rights reserved
The influence of thermal exposure on the γ′ precipitates characteristics and tensile behavior of superalloy IN-738LC
, Article Journal of Materials Processing Technology ; Volume 147, Issue 3 , 2004 , Pages 343-350 ; 09240136 (ISSN) ; Asgari, S ; Sharif University of Technology
2004
Abstract
The effects of long term aging on γ′ size and distribution and its influence on tensile behavior of superalloy IN-738LC at room and in elevated temperatures were investigated. Samples were aged isothermally at 850 °C for different times up to 3000 h and tensile tests were performed on samples in both standard heat treatment (SHT) and aged conditions. For samples in SHT condition yield stress (σy) was independent of tensile temperature up to 550 °C, after which it decreased slightly and then reached a maximum at 650 °C. Also minimum ductility was observed in this temperature. For aged samples, results showed an initial decrease of σy up to 550 °C, followed by a subsequent increase in σy...
The effect of thermal exposure on the γ′ characteristics in a Ni-base superalloy
, Article Journal of Alloys and Compounds ; Volume 368, Issue 1-2 , 2004 , Pages 144-151 ; 09258388 (ISSN) ; Asgari, S ; Sharif University of Technology
2004
Abstract
In this investigation, changes in γ′ characteristics in superalloy IN-738LC during aging are presented. The SEM studies revealed that coarsening kinetics of γ′ follows a linear law at different aging time for different temperatures. Whereas when coarsening of secondary γ′ is studied, it was found that at the early stage of aging, volume fraction of secondary γ′ is high, leading to short inter-particle distances. In this condition interfacial energy is dominant and variation of [r3-r03] as a function of aging time is linear. As the coarsening proceeds, volume fraction of secondary γ′ decreases and elastic interaction energy becomes dominant. In such case a deviation in variation of [r3-r03]...
Analytical Approach for Buckling Analysis of Generally Laminated Conical Shells under Axial Compression
, M.Sc. Thesis Sharif University of Technology ; Kouchakzadeh, Mohammad Ali (Supervisor)
Abstract
In this thesis, buckling of truncated conical shells made of composite laminates with general lamination sequence is investigated. The conical shell is considered under axial compression with simply supported or clamped boundary condition. First, Donnel type nonlinear equations and boundary conditions for doubly curved shells are obtained using Hamilton principle. Second, using adjacent equilibrium criterion, the nonlinear equations was linearized then with defining lame parameters and curvature radius, the linear equations of conical shell was extracted. The power series and Galerkin method was used to solve differential equations. The obtained results are in good agreement with available...
An analytical approach for buckling analysis of generally laminated conical shells under axial compression
, Article Acta Mechanica ; Volume 227, Issue 4 , 2016 , Pages 1181-1198 ; 00015970 (ISSN) ; Shakouri, M ; Kouchakzadeh, M. A ; Sharif University of Technology
Springer-Verlag Wien
2016
Abstract
In the present investigation, the buckling of generally laminated conical shells with various boundary conditions subjected to axial pressure is studied using an analytical approach. The governing equations are obtained using classical shell theory with Donnell assumptions in strain–deformation relations and the principle of minimum potential energy. The differential equations are solved using trigonometric functions in circumferential and power series in longitudinal directions. All types of boundary conditions can be applied in this method. The results are compared and validated with the results available in the literature, and good agreement is observed. Finally, the effects of the...
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....
Integration of adaptive neuro-fuzzy inference system, neural networks and geostatistical methods for fracture density modeling
, Article Oil and Gas Science and Technology ; Vol. 69, issue. 7 , 2014 , pp. 1143-1154 ; ISSN: 12944475 ; Kadkhodaie-Ilkhchi, A ; Sharghi, Y ; Ghaedi, M ; Sharif University of Technology
2014
Abstract
Image logs provide useful information for fracture study in naturally fractured reservoir. Fracture dip, azimuth, aperture and fracture density can be obtained from image logs and have great importance in naturally fractured reservoir characterization. Imaging all fractured parts of hydrocarbon reservoirs and interpreting the results is expensive and time consuming. In this study, an improved method to make a quantitative correlation between fracture densities obtained from image logs and conventional well log data by integration of different artificial intelligence systems was proposed. The proposed method combines the results of Adaptive Neuro-Fuzzy Inference System (ANFIS) and Neural...
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...