Loading...
Search for:
mohajer--d
0.128 seconds
Total 1798 records
Diffuse emissions of particles from iron ore piles by wind erosion
, Article Environmental Engineering Science ; Volume 28, Issue 5 , 2011 , Pages 333-339 ; 10928758 (ISSN) ; Torkian, A ; Sharif University of Technology
2011
Abstract
Industrial air pollution from point and nonpoint sources of steel complexes has drawn increasingly more public attention in the past decades. Previous research efforts have been more concentrated on point sources of particulate emissions from these complexes. However, wind-induced particulate emissions from iron ore storage piles not only result in ambient air pollution but also increase economic adverse effects to the industry by loss of process raw materials. Experiments were conducted to assess the impact of wind speed and humidity on particulate emission rates from iron ore storage piles. A wind-generating system and specific iron ore, experimental piles (L:W:H of 30:11.5:5 cm) were...
Performance Modeling Of Twin Shaft Gas Turbine as a Turbocomperessor
, M.Sc. Thesis Sharif University of Technology ; Ghorbanian, Kaveh (Supervisor)
Abstract
Gas turbines and centrifugal compressors are the preferred means of compressing the gas in pipeline systems. Both gas turbines and centrifugal compressors exhibit performance characteristics that depend on the operating point imposed on them by the pipeline operation. Simulation of gas turbine-driven centrifugal compressors is necessary for a variety of applications in the general area of pipeline simulation. This research focuses on modeling of twin shaft gas turbine dynamic and steady state performance. For this purpose, it was necessary to evaluate the thermodynamic working process of the gas turbine by using an in-house computer code. At design point, the calculations are solely based on...
Reactivity studies of biomimetic catalytic epoxidation of alkenes with tetrabutylammonium periodate in the presence of various manganese porphyrins and nitrogen donors: Significant axial ligand π-bonding effects
, Article New Journal of Chemistry ; Volume 28, Issue 6 , 2004 , Pages 740-747 ; 11440546 (ISSN) ; Karimipour, G ; Bagherzadeh, M ; Sharif University of Technology
Royal Society of Chemistry
2004
Abstract
Highly selective epoxidation (> 95%) of unfunctionalized alkenes was performed by tetrabutylammonium periodate in the presence of six different phenyl substituted manganese(III) meso-tetraphenylporphyrins [Mn(Por)] and imidazole in CH2Cl2. Electron-withdrawing and bulky substituents on the phenyl groups lowered the catalytic activities of the corresponding Mn(Por). Less bulky alkenes with electron -rich double bonds showed greater reactivity in the epoxidation. Co-catalytic activities of four different classes of axial nitrogen donors are compared in the presence of various Mn(Por). In general no direct correlation was found between co-catalytic activities and the pKa values of the nitrogen...
Guidance and Transportation of a Target Vessel by a SWARM Unmanned Surface Vehicles (USVs)
, M.Sc. Thesis Sharif University of Technology ; Sayyaadi, Hassan (Supervisor)
Abstract
This study presents the design and simulation of a system for guiding a target vessel using multiple autonomous tugboats (swarm tugboats). The main objective is to develop a coordinated control architecture and force allocation strategy capable of accurately guiding the target vessel along predefined reference trajectories while optimizing the interaction among the tugboats. In the initial phase, the dynamic model of the target vessel was developed based on the Newton–Euler equations. The model was validated through two approaches: (1) comparing the model’s outputs with analytical predictions derived from dynamic equations, and (2) verifying the model’s behavior against results reported in...
Randomized algorithms for comparison-based search
, Article Advances in Neural Information Processing Systems 24: 25th Annual Conference on Neural Information Processing Systems 2011, NIPS 2011, 12 December 2011 through 14 December 2011 ; December , 2011 ; 9781618395993 (ISBN) ; Diggavi, S ; Delgosha, P ; Mohajer, S ; Sharif University of Technology
2011
Abstract
This paper addresses the problem of finding the nearest neighbor (or one of the R-nearest neighbors) of a query object q in a database of n objects, when we can only use a comparison oracle. The comparison oracle, given two reference objects and a query object, returns the reference object most similar to the query object. The main problem we study is how to search the database for the nearest neighbor (NN) of a query, while minimizing the questions. The difficulty of this problem depends on properties of the underlying database. We show the importance of a characterization: combinatorial disorder D which defines approximate triangle inequalities on ranks. We present a lower bound of Ω(Dlog...
A new online random particles optimization algorithm for mobile robot path planning in dynamic environments
, Article Mathematical Problems in Engineering ; Volume 2013 , 2013 ; 1024123X (ISSN) ; Kiani, K ; Samiei, E ; Sharifi, M ; Sharif University of Technology
2013
Abstract
A new algorithm named random particle optimization algorithm (RPOA) for local path planning problem of mobile robots in dynamic and unknown environments is proposed. The new algorithm inspired from bacterial foraging technique is based on particles which are randomly distributed around a robot. These particles search the optimal path toward the target position while avoiding the moving obstacles by getting help from the robot's sensors. The criterion of optimal path selection relies on the particles distance to target and Gaussian cost function assign to detected obstacles. Then, a high level decision making strategy will decide to select best mobile robot path among the proceeded particles,...
The Study of Megawatt Wind Turbine Rotor Performance in Presence of Contamination Using CFD
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor) ; Taiebi Rahni, Mohammad (Supervisor)
Abstract
Considering the negative effects of contamination on wind turbine blade performance, we investigate aerodynamics performance of a one- Megawatt wind turbine. To achieve this, we compare the performance and power of the wind turbine with and without contaminations. To calculate the wind turbine output power, we use a developed wind turbine calculator, which benefits from the Blade Element Momentum (BEM) theory. Furthermore, the aerodynamics calculations are performed using of a commercial software for clean and rough airfoils. Considering the change of Reynolds number along the blade axis, the airfoil characteristics are calculated for two Reynolds numbers of 0.5 and 3.5 millions to increase...
Rayleigh Waves Propagation in a Piezoelectric Layered Half-space with Imperfect Interface
, M.Sc. Thesis Sharif University of Technology ; Eskandari, Morteza (Supervisor)
Abstract
The problem of the Rayleigh wave propagation in a piezoelectric layer overlying a piezoelectric half space by an imperfect interface is investigated. These days because of widespread use of the piezoelectric materials in sensors and transducers based on surface waves, the study of wave propagation in these medias is paid attention by many researchers. In this study, imperfection between layer and half-space idealized by springs which have determine values. If the stiffness of springs approaches to infinity, the interface will be perfect. Also, zero stiffness of springs indicates that there is no continuity between layer and half space. With the use of potential functions for displacement...
Diabetes-associated thigh muscle degeneration mediates knee osteoarthritis–related outcomes: results from a longitudinal cohort study
, Article European Radiology ; Volume 33, Issue 1 , 2023 , Pages 595-605 ; 09387994 (ISSN) ; Moradi, K ; Guermazi, A ; Dolatshahi, M ; Zikria, B ; Najafzadeh, N ; Kalyani, R. R ; Roemer, F. W ; Berenbaum, F ; Demehri, S ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2023
Abstract
Objectives: We examined the association between diabetes mellitus (DM) and longitudinal MRI biomarkers for thigh muscle degeneration in patients with knee osteoarthritis (KOA) and their mediatory role in worsening KOA-related symptoms. Methods: The Osteoarthritis Initiative (OAI) participants with radiographic KOA (Kellgren-Lawrence grade ≥ 2) were included. Thighs and corresponding knees of KOA patients with versus without self-reported DM were matched for potential confounders using propensity score (PS) matching. We developed and used a validated deep learning method for longitudinal thigh segmentation. We assessed the association of DM with 4-year longitudinal muscle degeneration in...
Role of Thigh Muscle Changes in Knee Osteoarthritis Outcomes: Osteoarthritis Initiative Data
, Article Radiology ; Volume 305, Issue 1 , 2022 , Pages 169-178 ; 00338419 (ISSN) ; Dolatshahi, M ; Moradi, K ; Najafzadeh, N ; Eng, J ; Zikria, B ; Wan, M ; Cao, X ; Roemer, F. W ; Guermazi, A ; Demehri, S ; Sharif University of Technology
Radiological Society of North America Inc
2022
Abstract
Background: Longitudinal data on the association of quantitative thigh muscle MRI markers with knee osteoarthritis (KOA) outcomes are scarce. These associations are of clinical importance, with potential use for thigh muscle–directed disease-modifying interventions. Purpose: To measure KOA-associated longitudinal changes in MRI-derived muscle cross-sectional area (CSA) and adipose tissue and their association with downstream symptom worsening and knee replacement (KR). Materials and Methods: In a secondary analysis of the Osteoarthritis Initiative multicenter prospective cohort (February 2004 through October 2015), knees of participants with available good-quality thigh MRI scans at baseline...
Data science and predictive analytics : biomedical and health applications using R
, Book
Springer International Publishing AG
2018
Synergistic effect of MEHPA on co-extraction of zinc and cadmium with DEHPA
, Article Minerals Engineering ; Volume 17, Issue 1 , 2004 , Pages 89-92 ; 08926875 (ISSN) ; Moradkhani, D ; Darvishi, D ; Askari, M ; Behnian, D ; Sharif University of Technology
2004
Abstract
Simultaneous extraction of zinc and cadmium by a mixture of di-2-ethyl hexyl phosphoric acid (DEHPA) and mono-2-ethyl hexyl phosphoric acid (MEHPA), and the synergistic effect of MEHPA on co-extraction of zinc and cadmium with DEHPA have been investigated. It was shown that the extraction of zinc and cadmium by DEHPA and/or MEHPA can be increased by an increase of pH. The results also illustrate that the pH0.5 of zinc, by increase in MEHPA from 0.1 to 8 vol%, did not vary significantly while that of cadmium varies from 0.63 to 2.4. In other words MEHPA prevents selective extraction of zinc from aqueous media containing both zinc and cadmium. Studies on the selective separation parameter...
Investigating the convective flow of ternary hybrid nanofluids and single nanofluids around a stretched cylinder: Parameter analysis and performance enhancement
, Article International Journal of Thermofluids ; Volume 23 , 2024 ; 26662027 (ISSN) ; Hosseinzadeh, K ; Ganji, D. D ; Sharif University of Technology
2024
Abstract
Within this research, we examined the convective flow of a blend of ternary hybrid nanofluids and single nanofluids with a stagnation point caused by a stretched cylinder. The purpose of this study is to investigate the effect of using a ternary hybrid nanofluid instead of a single nanofluid. Water is used as the base fluid in this investigation. The single nanofluid is made of copper and the ternary hybrid nanofluid is made of Molybdenum disulfide, copper, and silver. The impact of the curvature parameter, nanoparticle volume fraction, mixed convection parameter, velocity ratio, shape factor, conjugate number and Eckert number parameters on temperature and velocity profiles has been...
MHD flow in a channel using new combination of order of magnitude technique and HPM [MHD tok u kanalu uporabom novih kombinacija tehnika grubog opisa vrijednosti i HPM]
, Article Tehnicki Vjesnik ; Volume 21, Issue 2 , April , 2014 , Pages 317-321 ; ISSN: 13303651 ; Ganji, D. D ; Rahni, M. T ; Sharif University of Technology
2014
Abstract
The present work is concerned with the steady incompressible flow through a parallel plate channel with stretching walls under an externally applied magnetic field. The governing continuity and Navier-Stokes equations are reduced to a fourth order nonlinear differential equation by using vorticity definition and similarity solution transformation. The obtained equations are solved by applying the analytical homotopy perturbation method (HPM). The method is called order of magnitude suggested for simplifying series solution to finite expression that is useful in engineering problems. The results are verified by comparing with numerical solutions and demonstrate a good accuracy of the obtained...
Analytical solution of nonlinear differential equations two oscillators mechanism using Akbari-Ganji method
, Article Modern Physics Letters B ; Volume 35, Issue 31 , 2021 ; 02179849 (ISSN) ; Hosseinzadeh, K ; Rahai, M ; Ganji, D. D ; Sharif University of Technology
World Scientific
2021
Abstract
In the last decade, many potent analytical methods have been utilized to find the approximate solution of nonlinear differential equations. Some of these methods are energy balance method (EBM), homotopy perturbation method (HPM), variational iteration method (VIM), amplitude frequency formulation (AFF), and max-min approach (MMA). Besides the methods mentioned above, the Akbari-Ganji method (AGM) is a highly efficient analytical method to solve a wide range of nonlinear equations, including heat transfer, mass transfer, and vibration problems. In this study, it was constructed the approximate analytic solution for movement of two mechanical oscillators by employing the AGM. In the derived...
A compiler for multi-key homomorphic signatures for Turing machines
, Article Theoretical Computer Science ; Volume 889 , 2021 , Pages 145-170 ; 03043975 (ISSN) ; Fiore, D ; Venturi, D ; Amini, M ; Sharif University of Technology
Elsevier B.V
2021
Abstract
At SCN 2018, Fiore and Pagnin proposed a generic compiler (called “Matrioska”) allowing to transform sufficiently expressive single-key homomorphic signatures (SKHSs) into multi-key homomorphic signatures (MKHSs) under falsifiable assumptions in the standard model. Matrioska is designed for homomorphic signatures that support programs represented as circuits. The MKHS schemes obtained through Matrioska support the evaluation and verification of arbitrary circuits over data signed from multiple users, but they require the underlying SKHS scheme to work with circuits whose size is exponential in the number of users, and thus can only support a constant number of users. In this work, we propose...
Ride comfort of high-speed trains travelling over railway bridges
, Article Vehicle System Dynamics ; Volume 43, Issue 3 , 2005 , Pages 173-197 ; 00423114 (ISSN) ; Younesian, D ; Thompson, D ; Jones, C ; Sharif University of Technology
Taylor and Francis Ltd
2005
Abstract
The ride comfort of high-speed trains passing over railway bridges is studied in this paper. A parametric study is carried out using a time domain model. The effects of some design parameters are investigated such as damping and stiffness of the suspension system and also ballast stiffness. The influence of the track irregularity and train speed on two comfort indicators, namely Sperling's comfort index and the maximum acceleration level are also studied. Two types of railway bridges, a simple girder and an elastically supported bridge are considered. Timoshenko beam theory is used for modelling the rail and bridge and two layers of parallel damped springs in conjunction with a layer of mass...
Entropy generation analysis of kerosene oil flow with ternary hybrid nanoparticles on the stretchable exponential surface
, Article International Journal of Modelling and Simulation ; 2024 ; 02286203 (ISSN) ; Hosseinzadeh, K ; Najafpour, A ; Ganji, D. D ; Sharif University of Technology
2024
Abstract
In this research, the flow of kerosene oil with ternary hybrid nanoparticles on a stretchable exponential surface has been investigated. There is also a discussion about the entropy analysis of the flow of hydromagnetic radiation by the surface. The ternary hybrid nanofluid (THyNF) contains graphene oxide (GO), magnesium oxide (MgO), and zinc oxide (ZnO) as nanoparticles and kerosene oil as a base fluid. Using useful transformations, differential equations with partial derivatives (PDEs) were transformed into ordinary differential equations (ODEs). Then, the ODEs were solved using the RK5th method. Furthermore, the impacts of parameters like radiation parameter ((Formula presented.)),...
The investigation of pre-ionization effect on the improvement of pinch quality and increased hard X-ray radiation in a dense plasma focus (DPF) device
, Article Journal of Fusion Energy ; Volume 43, Issue 1 , 2024 ; 01640313 (ISSN) ; Vosoughi, N ; Mahabadi, T. D ; Piriaei, D ; Sharif University of Technology
2024
Abstract
This study delves into the impact of the pre-ionization technique, facilitated by an optimal shunt resistor, on a DPF device operating with deuterium gas. The investigation unveils enhancements in critical parameters within the plasma column environment during the pinch phase, specifically the total and plasmoid hard x-ray yields. Employing a combination of time-resolved detectors, such as plastic scintillator and magnetic probe arrays, alongside time-integrated detectors like pinhole camera, and just by using this technique, the research illustrated an augmented plasma sheath velocity during the axial phase. Notably and other than the enhancement of hard x-ray yield, the optimal pressure of...
Heat transfer hybrid nanofluid (1-Butanol/MoS2–Fe3O4) through a wavy porous cavity and its optimization
, Article International Journal of Numerical Methods for Heat and Fluid Flow ; 2020 ; Montazer, E ; Shafii, M. B ; Ganji, D. D ; Sharif University of Technology
Emerald Group Holdings Ltd
2020
Abstract
Purpose: The purpose of this paper is to investigate natural convection in a porous wavy-walled enclosure that is including a cylinder cavity in the middle of it and filled with a hybrid nanofluid contains 1-Butanol as the base fluid and MoS2–Fe3O4 hybrid nanoparticles. Design/methodology/approach: The domain of interest is bounded by constant temperature horizontal corrugated surfaces and isothermal vertical flat surfaces. The numerical outputs are explained in the type of isotherms, streamline and average Nusselt number with variations of the Rayleigh number, Hartmann number, nanoparticle shape factor and porosity of the porous medium. For solving the governing equations, the finite...