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) Afshar Mohajer, N ; 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 Mohajer Darabi, Abbas (Author) ; 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) Mohajer, D ; 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...

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) Tschopp, D ; 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) Mohajer, B ; 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 Mohajer, Abbas (Author) ; 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 Sheikh Bagher Mohajer, Mohammad Mahdi (Author) ; 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) Mohajer, B ; 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) Mohajer, B ; 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...

Microwave-induced Cannizzaro reaction over neutral γ-alumina as a polymeric catalyst [electronic resource]

, Article Reactive and Functional Polymers ; 01/2002; 51(1):49-53 Pourjavadi, A. (Ali) ; Soleimanzadeh, B ; Marandi, G. B

Abstract

γ-Alumina is used to catalyze the Cannizzaro reaction in the absence of any base under microwave irradiation in high yields. In the case of terephthalaldehyde the reaction is carried out with high selectivity

SnCl4/SiO2: an efficient heterogeneous alternative for one-pot synthesis of β-acetamidoketones

, Article Journal of the Chinese Chemical Society ; Volume 56, Issue 2 , 2009 , Pages 386-391 ; 00094536 (ISSN) Mirjalili, B. B. F ; Mahmoodi Hashemi, M ; Sadeghi, B ; Emtiazi, H ; Sharif University of Technology

2009

Abstract

Enolizable ketones have been reacted in a one-pot method with aromatic aldehydes, acetyl chloride and acetonitrile at room temperature in the presence of SnCl4/SiO2 to furnish the corresponding β-acetamidoketones in improved yields. Acetylation of an aromatic hydroxyl group was observed while using 4-hydroxybenzaldehyde or vanillin and the corresponding β-acetamidoketones were isolated in an excellent yield

Turbulent flow in converging nozzles, part one: Boundary layer solution

, Article Applied Mathematics and Mechanics (English Edition) ; Volume 32, Issue 5 , 2011 , Pages 645-662 ; 02534827 (ISSN) Maddahian, R ; Farhanieh, B ; Firoozabadi, B ; Sharif University of Technology

2011

Abstract

The boundary layer integral method is used to investigate the development of the turbulent swirling flow at the entrance region of a conical nozzle. The governing equations in the spherical coordinate system are simplified with the boundary layer assumptions and integrated through the boundary layer. The resulting sets of differential equations are then solved by the fourth-order Adams predictor-corrector method. The free vortex and uniform velocity profiles are applied for the tangential and axial velocities at the inlet region, respectively. Due to the lack of experimental data for swirling flows in converging nozzles, the developed model is validated against the numerical simulations. The...

Numerical investigation of steady density currents flowing down an incline using v2̄ - F turbulence model

, Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 129, Issue 9 , 2007 , Pages 1172-1178 ; 00982202 (ISSN) Khakzad, N ; Firoozabadi, B ; Farhanieh, B ; Sharif University of Technology

2007

Abstract

The governing equations of two-dimensional steady density currents are solved numerically using a finite volume method. The v2̄-f turbulence model, based on standard k - s model, is used for the turbulence closure. In this method, all Reynolds stress equations are replaced with both a transport equation for v2̄ and an elliptic relaxation equation for f, a parameter closely related to the pressure strain redistribution term. The Simple-C procedure is used for pressure-velocity coupling. In addition, Boussinesq's approximation is used to obtain the momentum equation. The computed height of the progressive density current is compared to the measured data in the literature, resulting in good...

Numerical simulation of turbid-density current using v2̄ - f turbulence model

, Article 2005 ASME International Mechanical Engineering Congress and Exposition, IMECE 2005, Orlando, FL, 5 November 2005 through 11 November 2005 ; Volume 261 FED , 2005 , Pages 619-627 ; 08888116 (ISSN); 0791842193 (ISBN); 9780791842195 (ISBN) Mehdizadeh, A ; Firoozabadi, B ; Farhanieh, B ; Sharif University of Technology

2005

Abstract

The deposition behavior of fine sediment is an important phenomenon, and yet unclear to engineers concerned about reservoir sedimentation. An elliptic relaxation turbulence model (v2̄ - f model) has been used to simulate the motion of turbid density currents laden whit fine solid particles. During the last few years, the v2̄ - f turbulence model has become increasingly popular due to its ability to account for near-wall damping without use of damping functions. In addition, it has been proved that the v2̄ - f model to be superior to other RANS methods in many fluid flows where complex flow features are present. Due to low Reynolds number turbulence of turbidity current,(its critical Reynolds...

Analytical solution for creeping motion of a viscoelastic drop falling through a Newtonian fluid

, Article Korea Australia Rheology Journal ; Vol. 26, issue. 1 , 2014 , pp. 91-104 ; ISSN: 1226119X Vamerzani, B. Z ; Norouzi, M ; Firoozabadi, B ; Sharif University of Technology

2014

Abstract

In this paper, an analytical solution for steady creeping motion of viscoelastic drop falling through a viscous Newtonian fluid is presented. The Oldroyd-B model is used as the constitutive equation. The analytical solutions for both interior and exterior flows are obtained using the perturbation method. Deborah number and capillary numbers are considered as the perturbation parameters. The effect of viscoelastic properties on drop shape and motion are studied in detail. The previous empirical studies indicated that unlike the Newtonian creeping drop in which the drop shape is exactly spherical, a dimpled shape appears in viscoelastic drops. It is shown that the results of the present...

Theoretical and experimental study on the motion and shape of viscoelastic falling drops through Newtonian media

, Article Rheologica Acta ; Volume 55, Issue 11-12 , 2016 , Pages 935-955 ; 00354511 (ISSN) Vamerzani, B. Z ; Norouzi, M ; Firoozabadi, B ; Sharif University of Technology

Springer Verlag 2016

Abstract

In this paper, creeping motion of a viscoelastic drop falling through a Newtonian fluid is investigated experimentally and analytically. A polymeric solution of 0.08 % xanthan gum in 80:20 glycerol/water and silicon oil is implemented as the viscoelastic drop and the bulk viscous fluids, respectively. The shape and motion of falling drops are visualized using a high speed camera. The perturbation technique is employed for both interior and exterior flows, and Deborah and capillary numbers are considered as perturbation parameters up to second order. The product of Deborah and capillary numbers is also used as a perturbation parameter to apply the boundary condition on the deformation on the...

Minimizing uplink delay in delay-sensitive 5G CRAN platforms

, Article 2nd IEEE 5G World Forum, 5GWF 2019, 30 September 2019 through 2 October 2019 ; 2019 , Pages 154-160 ; 9781728136271 (ISBN) Ataie, A ; Kanaanian, B ; Khalaj, B. H ; Sharif University of Technology

Institute of Electrical and Electronics Engineers Inc 2019

Abstract

In this paper, we consider the problem of minimizing the uplink delays of users in a 5G cellular network. Such cellular network is based on a Cloud Radio Access Network (CRAN) architecture with limited fronthaul capacity, where our goal is to minimize delays of all users through an optimal resource allocation. Earlier works minimize average delay of each user assuming same transmit power for all users. Combining Pareto optimization and Markov Decision Process (MDP), we show that every desired balance in the trade-off among infinite-horizon average-reward delays, is achievable by minimizing a properly weighted sum delays. In addition, we solve the problem in two realistic scenarios;...

Microwave-induced Cannizzaro reaction over neutral γ-alumina as a polymeric catalyst

, Article Reactive and Functional Polymers ; Volume 51, Issue 1 , 2002 , Pages 49-53 ; 13815148 (ISSN) Pourjavadi, A ; Soleimanzadeh, B ; Marandi, G. B ; Sharif University of Technology

2002

Abstract

Microwave induced Cannizzaro reaction, which was performed in presence of neutral γ-alumina as a polymeric catalyst, was discussed. Cannizzaro reaction was carried out on alumina surface and other unknown products were also obtained. Solvent extraction method was utilized to isolate mild and selective benzyl alcohol and carboxylic acids

Feedback bit reduction for antenna selection methods in wireless systems

, Article 2005 13th IEEE International Conference on Networks jointly held with the 2005 7th IEEE Malaysia International Conference on Communications, Kuala Lumpur, 16 November 2005 through 18 November 2005 ; Volume 1 , 2005 , Pages 229-233 ; 1424400007 (ISBN); 9781424400003 (ISBN) Shariatpanahi, P ; Babadi, B ; Hossein Khalaj, B ; Sharif University of Technology

2005

Abstract

A well known method to reduce the intrinsic complexity of Multiple Input Multiple Output (MIMO) systems is to choose a subset of available antennas which have stronger links than the others, in order to perform the specified MIMO algorithm. The data resulted from the antenna selection process (at the receiver side) is sent back to the transmitter side via a feedback channel. There seems to be a need to reduce the number of feedack bits, specially when the number of antennas is not small. In this paper, we investigate the problem of reducing the number of feedback bits in antenna selection techniques. We've proposed two methods using vector quantization techniques to perform feedback bit...

A distributed locality-aware neighbor selection algorithm for P2P video streaming over wireless mesh networks

, Article 2012 6th International Symposium on Telecommunications, IST 2012 ; 2012 , Pages 639-643 ; 9781467320733 (ISBN) Moayeri, F ; Akbari, B ; Khansari, M ; Ahmadifar, B ; Sharif University of Technology

2012

Abstract

Nowadays, deployment of peer-to-peer video streaming systems over wireless mesh networks has attained raising popularity among large number of users around the world. In this paper, we present an efficient peer-to-peer live video streaming architecture over multi-hop wireless mesh networks. In our proposed architecture, we take the physical topology of network into account and based on a distributed distributed locality-aware neighbor selection algorithm in the overlay construction phase, we generate an efficient mesh-based overlay on top of wireless mesh networks. In locality-aware neighbor selection algorithm, instead of choosing randomly, peers find their best neighbors based on their...