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Nonlinear vibrations of a rotor on nonlinear tilting-pad-journal-bearings
, Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Volume 43, Issue 3 , February , 2021 ; 16785878 (ISSN) ; Mohammad Navazi, H ; Haddadpour, H ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
In this paper, the coupled equations of nonlinear vibrations of a rigid two-dimensional rotor supported on tilting-pad-journal-bearing under harmonic excitation have been studied using second-order multiple scales method. By considering a nonlinear quadratic model for tilting-pad-journal-bearings, the governing coupled nonlinear differential equations of motion are presented. The frequency response function of the system, the effect of excitation force on the response, and stability of the system are discussed in different operating conditions using the method of multiple scales and validated with a numerical method. The results show that the system may have hardening or softening behavior...
Finding the best station in Belgium to use residential-scale solar heating, One-year dynamic simulation with considering all system losses: Economic analysis of using ETSW
, Article Sustainable Energy Technologies and Assessments ; Volume 45 , June , 2021 ; 22131388 (ISSN) ; Jahangiri, M ; Mosavi, A ; Jalaladdin Hosseini Dehshiri, S ; Shahabaddin Hosseini Dehshiri, S ; Ebrahimi, S ; Al Sadat Etezadi, Z ; Karimipour, A ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The main purpose of this study is to provide the heating power for space heating and sanitary hot water for a residential house in sixteen stations located in Belgium using evacuated tube solar water (ETSW). A one-year dynamic simulation was performed using TSOL 5.5 software and Meteonorm 7.1 was used to obtain the climatic data. Technical and environmental studies as well as station rankings are the parameters that have been examined for the first time in the present study. The weighting results of using the Best-Worst method (BWM) revealed that total solar fraction and CO2 emission avoided have the highest and lowest weight, respectively. Station ranking was performed using ARAS technique...
A general approach for mutual information minimization and its application to blind source separation
, Article Signal Processing ; Volume 85, Issue 5 SPEC. ISS , 2005 , Pages 975-995 ; 01651684 (ISSN) ; Jutten, C ; Sharif University of Technology
Elsevier
2005
Abstract
In this paper, a nonparametric "gradient" of the mutual information is first introduced. It is used for showing that mutual information has no local minima. Using the introduced "gradient", two general gradient based approaches for minimizing mutual information in a parametric model are then presented. These approaches are quite general, and principally they can be used in any mutual information minimization problem. In blind source separation, these approaches provide powerful tools for separating any complicated (yet separable) mixing model. In this paper, they are used to develop algorithms for separating four separable mixing models: linear instantaneous, linear convolutive, post...
Jet into cross flow boundary layer control an innovation in gas turbine blade cooling
, Article 35th AIAA Fluid Dynamics Conference and Exhibit, Toronto, ON, 6 June 2005 through 9 June 2005 ; 2005 ; 9781624100598 (ISBN) ; Taeibi Rahni, M ; Darbandi, M ; Sharif University of Technology
2005
Abstract
New standpoint of turbulent coolant jets into crossflow, which have numerous applications in traditional and modern technology, especially in gas turbine blades, is presented in this work. It is more than half a century that, many researchers have been studying jet into cross flow to understand its behavior and to predict and control it better. Previous studies indicate that, the main attentions had been on: a- geometrical parameters such as: inclined and compound jet angles, hole's shape, jet's array arrangements, jet's spacing, and jet's channel depth, b- flow characteristics like: blowing ratio, density ratio, jet and cross flow Reynolds numbers, and turbulence intensity. Here, we have...
An adaptive call admission algorithm for cellular networks
, Article Computers and Electrical Engineering ; Volume 31, Issue 2 , 2005 , Pages 132-151 ; 00457906 (ISSN) ; Meybodi, M. R ; Sharif University of Technology
2005
Abstract
In this paper, we first propose a new continuous action-set learning automaton and theoretically study its convergence properties and show that it converges to the optimal action. Then we give an adaptive and autonomous call admission algorithm for cellular mobile networks, which uses the proposed learning automaton to minimize the blocking probability of the new calls subject to the constraint on the dropping probability of the handoff calls. The simulation results show that the performance of the proposed algorithm is close to the performance of the limited fractional guard channel algorithm for which we need to know all the traffic parameters in advance. © 2005 Elsevier Ltd. All rights...
Numerical modeling of interaction between flexible retaining wall and saturated clayey soil in undrained and drained conditions
, Article 4th International Conference on Soft Soil Engineering - Soft Soil Engineering, Vancouver, BC, 4 October 2006 through 6 October 2006 ; 2007 , Pages 493-498 ; 0415422809 (ISBN); 9780415422802 (ISBN) ; Pak, A ; Sharif University of Technology
2007
Abstract
In this article, behavior of cantilever retaining walls with various flexibilities, which retain saturated cohesive soil behind, is studied using numerical modeling. Generally, pattern of lateral earth pressure behind retaining walls is complex and this complexity becomes greater for clayey soils. In this investigation, effects of different wall bending stiffnesses, and backfill drainage conditions on the failure height and on the lateral earth pressure are investigated using finite elements. Comparison between the obtained results from numerical simulation and those based on empirical or conventional design methods indicate that soil-structure interaction and c drainage conditions play...
Experimental and numerical investigation of thermal enhancement methods on rammed-earth materials
, Article Solar Energy ; Volume 244 , 2022 , Pages 474-483 ; 0038092X (ISSN) ; Samadianfard, S ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
The renewed attention paid to rammed earth materials in recent decades is related to their sustainability, high thermo-buffering capacity and relatively low cost. The energy performance of rammed earth materials can be enhanced with stabilization. However, some of thermal enhancement methods have destructive side-effects. In the current study, the effect of three different methods was investigated on thirteen different alternatives of rammed earth materials to improve energy efficiency of buildings. These methods include using phase change materials, cementitious admixtures and external insulators. Thermo-dynamic parameters such as time lag, thermal conductivity and heat flux were measured...
Vibration of a Circular plate on Pasternak foundation with variable modulus due to moving mass
, Article Structural Engineering and Mechanics ; Volume 83, Issue 6 , 2022 , Pages 757-770 ; 12254568 (ISSN) ; Foyouzat, M. A ; Mofid, M ; Sharif University of Technology
Techno-Press
2022
Abstract
In this paper, the vibration of a moderately thick plate to a moving mass is investigated. Pasternak foundation with a variable subgrade modulus is considered to tackle the shortcomings of Winkler model, and an analytical-numerical solution is proposed based on the eigenfunction expansion method. Parametric studies by using both CPT (Classical Plate Theory) and FSDT (First-Order Shear Deformation Plate Theory) are carried out, and, the differences between them are also highlighted. The obtained results reveal that utilizing FSDT without considering the rotary inertia leads to a smaller deflection in comparison with CPT pertaining to a thin plate, while it demonstrates a greater response for...
Research on the effect of transients of high-voltage power supplies on the lifetime of high-power vacuum tubes: A microscopic assessment
, Article IEEE Transactions on Plasma Science ; Volume 50, Issue 11 , 2022 , Pages 4700-4708 ; 00933813 (ISSN) ; Ziaoddini, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
Electron guns are used as the electron sources in high-power electron tubes. The generated electron beam in electric guns passes through an aperture at the center of the anode. Since the electron beam has considerable kinetic energy, any collision between the electron beam and the anode aperture edge damages the electron gun. Therefore, electron guns are designed to meet the compatibility between the diameters of the electron beam and the anode aperture. However, this compatibility is disrupted during the transient time interval of the gun's power supply. In this article, the cause of failure of the electron gun of high-power electron tubes is investigated for the transient interval of the...
Elastic responses of bi-material media reinforced by interfacial thin films under asymmetric loading
, Article International Journal of Solids and Structures ; Volume 254-255 , 2022 ; 00207683 (ISSN) ; Jarfi, H ; Eskandari, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
In this paper, the elastic solution to the problem of an isotropic bi-material full-space reinforced by a perfectly bonded thin film across the media interface and subjected to arbitrary asymmetric interfacial loading is addressed. To not include any simplifications, the thin film is first considered as a layer having a finite thickness, and with the aid of Fourier expansion of Muki's potential functions in Hankel transformed space, the formulation of the problem is obtained for a tri-material full-space. Then, knowing that the flexural stiffness of the thin film is negligible, its thickness and shear modulus are assumed to tend to zero and infinity, respectively, such that its in-plane...
A deep learning approach for the solution of probability density evolution of stochastic systems
, Article Structural Safety ; Volume 99 , 2022 ; 01674730 (ISSN) ; Khodabakhsh, A. H ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Derivation of the probability density evolution provides invaluable insight into the behavior of many stochastic systems and their performance. However, for most real-time applications, numerical determination of the probability density evolution is a formidable task. The latter is due to the required temporal and spatial discretization schemes that render most computational solutions prohibitive and impractical. In this respect, the development of an efficient computational surrogate model is of paramount importance. Recent studies on the physics-constrained networks show that a suitable surrogate can be achieved by encoding the physical insight into a deep neural network. To this aim, the...
Reconfigurable intelligent surface-aided emitter localization
, Article IEEE Sensors Journal ; Volume 22, Issue 22 , 2022 , Pages 21866-21876 ; 1530437X (ISSN) ; Karbasi, S. M ; Behroozi, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
Localization of radio-frequency (RF) transmitters using time difference of arrival (TDOA)-based methods is one of the conventional passive techniques that admits noncooperative source position finding, but suffers from challenging requirements such as precise intersensor synchronization and high-throughput transmission data links. A tradeoff governing the TDOA systems is in the sensor placement configuration. The more distance the sensors are placed, the more accurate localization is carried out, while the cost for the synchronization and data link increases, at the same time. In this work, a novel reconfigurable intelligent surface (RIS)-aided localization system is proposed that enjoys...
Design and fabrication of a micro-opto-mechanical-systems accelerometer based on intensity modulation of light fabricated by a modified deep-reactive-ion-etching process using silicon-on-insulator wafer
, Article Journal of Vacuum Science and Technology B ; Volume 40, Issue 4 , 2022 ; 21662746 (ISSN) ; Gharooni, M ; Salarieh, H ; Akbari, J ; Sharif University of Technology
AVS Science and Technology Society
2022
Abstract
Accelerometers that work based on intensity modulation of light are more sensitive, economically feasible, and have a simpler fabrication process compared to wavelength modulation. A micro-opto-electro-mechanical-system accelerometer based on intensity modulation of light is designed and fabricated. A movable shutter that is attached to the proof mass is designed to change the intensity of light. Moreover, the mechanical part is designed to improve the overall sensitivity and linear behavior in the measurement range. The designed accelerometer is fabricated by a deep-reactive-ion-etching (DRIE) process. The DRIE process used in this report is based on a Bosch-like process, which uses SF 6...
An innovative inverse analysis based on the Bayesian inference for concrete material
, Article Ultrasonics ; Volume 124 , 2022 ; 0041624X (ISSN) ; Toufigh, V ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Nondestructive tests and evaluations are robust techniques for inspecting different attributes of concrete configuration. However, most nondestructive techniques focused on an aspect of concrete configuration based on comparison to other samples. In this paper, an innovative inverse analysis technique was developed to inspect different attributes of concrete configuration simultaneously. The methodology was based on the scattering feature of the ultrasonic waves during propagation in heterogeneous media. The transition matrix method was employed to determine the scattered wavefield. This method considers the shape of objects, unlike most other numerical methods. Furthermore, a novel...
A compatible mixed finite element method for large deformation analysis of two-dimensional compressible solids in spatial configuration
, Article International Journal for Numerical Methods in Engineering ; Volume 123, Issue 15 , 2022 , Pages 3530-3566 ; 00295981 (ISSN) ; Sharif University of Technology
John Wiley and Sons Ltd
2022
Abstract
In this article, a new mixed finite element formulation is presented for the analysis of two-dimensional compressible solids in finite strain regime. A three-field Hu–Washizu functional, with displacement, displacement gradient and stress tensor considered as independent fields, is utilized to develop the formulation in spatial configuration. Certain constraints are imposed on displacement gradient and stress tensor so that they satisfy the required continuity conditions across the boundary of elements. From theoretical standpoint, simplex elements are best suited for the application of continuity constraints. The techniques that are proposed to implement the constraints facilitate their...
A high-order nodal discontinuous Galerkin method for simulation of three-dimensional non-cavitating/cavitating flows
, Article Finite Elements in Analysis and Design ; Volume 200 , 2022 ; 0168874X (ISSN) ; Hejranfar, K ; Sharif University of Technology
Elsevier B.V
2022
Abstract
In this study, the nodal discontinuous Galerkin method is formulated in three-dimensions and applied to simulate three-dimensional non-cavitating/cavitating flows. For this aim, the three-dimensional preconditioned Navier-Stokes equations based on the artificial compressibility approach considering appropriate source terms to model cavitating phenomena are used. The spatial derivative terms in the resulting equations are discretized by utilizing the nodal discontinuous Galerkin method on tetrahedral elements and the derivative of the solution vector with respect to the artificial time is discretized by applying an explicit time integration method. An artificial viscosity method is formulated...
Low-speed wind energy harvesting from a vibrating cylinder and an obstacle cylinder by flow-induced vibration effect
, Article International Journal of Environmental Science and Technology ; Volume 19, Issue 3 , 2022 , Pages 1261-1272 ; 17351472 (ISSN) ; Shariatzadeh, M. J ; Bijarchi, M. A ; Pournasiri Masouleh, E ; Shafii, M. B ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
An experimental setup has been developed to analyse the impact of cylinder transverse vibration caused by flow-induced vibration, and to improve wind energy harvesting from these vibrations. The setup consists of a cylinder mounted on four springs and is subjected to a uniform and steady flow of wind. In the first part, the effect of mounting a fixed cylinder as an obstacle with different diameters and distances from the downstream vibrating cylinder is investigated. It has been observed that the vibration amplitude on the wake of an unequal-sized obstacle is greatly amplified compared to the case of a single cylinder or an equal-sized cylinder. Numerical simulations has been conducted to...
Conical localization from angle measurements: an approximate convex solution
, Article IEEE Sensors Letters ; Volume 6, Issue 5 , 2022 ; 24751472 (ISSN) ; Behnia, F ; Amiri, R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
For several years, a substantial effort has been devoted to the study of 3-D source localization based on 2-D arrays by measuring the well-known azimuth and elevation angles. However, studies on 3-D source localization performed by 1-D arrays are still lacking. Perhaps, the most important drawback in the deployment of a 2-D array structure lies in the fact that it needs a planar space, which might not be available in some applications. This letter concentrates on the problem of 3-D source localization based on 1-D angle measurement provided by a linear array. Different from the traditional 2-D structures where each measurement induces a straight line, each measurement in the 1-D array...
Peer-to-Peer energy sharing among smart energy hubs in an integrated heat-electricity network
, Article Electric Power Systems Research ; Volume 206 , 2022 ; 03787796 (ISSN) ; Sheikhi, A ; Ashouri Zadeh, A ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
By increasing the penetration level of the combined heat and power systems and demand response programs between energy consumers in the distribution network, the interaction between electricity and the natural gas network becomes more complicated. This paper proposes a peer-to-peer (P2P) energy sharing scheme for energy trading among Smart Energy Hubs (S.E. Hubs) which can trade both electrical and thermal energy with each other to reduce their cost and, reduce their dependency to gas and electricity utility companies. A two-stage energy strategy is presented. In the first stage, the S.E. Hubs total social cost is reduced by finding the optimal energy sharing profiles. And, in the second...
Quasi-linearization analysis for heat and mass transfer of magnetically driven 3rd-grade (Cu-TiO2/engine oil) nanofluid via a convectively heated surface
, Article International Communications in Heat and Mass Transfer ; Volume 135 , 2022 ; 07351933 (ISSN) ; Faridi, A. A ; Ahmad, S ; Jamshed, W ; Khan, N ; Alam, M. M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
The features of heat transferral capability between metallic (Cu) and non-metallic (TiO2) nanoparticles suspended in the engine-oil (EO) third-grade base-liquid has been analysed under the influence of strong magnetic field. The numerical investigation of system of coupled differential equations for third-grade nanofluid flow model is accomplished via Quasi-linearization method (QLM). The stretching horizontal sheet is heated through convective heat process assuming the special effects of thermal radiation, joule heating, heat generation and viscous dissipation in the energy equation. The mass suction and slip velocity at the boundary of the sheet has been taken into account to enhance...