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Formulation of Geometrically Nonlinear Microbeams Based on the Second Strain Gradient Theory
, M.Sc. Thesis Sharif University of Technology ; Asghari, Mohsen (Supervisor) ; Vatankhah, Ramin (Supervisor)
Abstract
Nowadays, the usage of beam-shaped structures has widely spread in micro- and nano-electromechanical systems; consequently, scholars are extremely interested in precise modeling of static and dynamic behaviors of them. As the beams utilized in MEMS and NEMS structures have thicknesses in the order of microns and sub-microns, the experimentally validated small scale effects would be considerable in their behavior. In fact, experiments manifest that the size-dependent behavior is an intrinsic feature of materials when they are used in small-scale structures. In the classical continuum mechanics, there exists no material length scale parameter. Thus, the classical theory is unable to capture...
Passage-Way Identification and Crossing Control of an Experimental Swarm Robot
, M.Sc. Thesis Sharif University of Technology ; Alasti, Aria (Supervisor) ; Vatankhah, Ramin (Co-Advisor)
Abstract
The aim of the proposed thesis is to devise a method of passage-way identification and crossing control of an experimental swarm robot. In the previous works done in the Sharif University of Technology, The main focus was on the collective behaviours than can be emeged from a swarm robot. Collective behaviours are such a primitive behaviours that are combined in order to lead to a real mission. In this investigation, the main focus is on the design of a mission. In this way, by combining the aggregation-divegance, chain formation, leader following and wall following collective behaviours, the desired is fulfilled. The algorithms is so that in the first stage, the agents of the swarm...
Control and Optimization of Robotic Swarm Flocking Using Naturally Inspired Methods
, M.Sc. Thesis Sharif University of Technology ; Alasty, Aria (Supervisor)
Abstract
The idea of using groups of simple autonomous robots instead of one or limited number of very sophisticated robots is inspired by flocking behaviors of animals. Distributed control structures and artificial swarming have attracted lots of studies in robotics. There are many applications for robotic swarms in which members are very simple robots with low communication capabilities. These robots communicate only within very limited distances. In this thesis, a homogenous robotic swarm with at least two robots is assumed. Swarm robots are considered to be dimensionless with no time delay, which is a normal assumption in this field of studies. Robots move in planar space and their behaviors are...
Vibration Control of Nonclassical Microbeams Using Boundary Control Theory of Partial Differential Equations
, Ph.D. Dissertation Sharif University of Technology ; Alasty, Aria (Supervisor)
Abstract
Nowadays, continuous systems such as strings, bars, beams and plates have become widespread in science and engineering applications. To achieve the control purposes of continuous systems, most of engineers use discretization techniques to reduce the governing partial differential equation (PDE) into a set of ordinary differential equations (ODEs). From practical point of view, this model reduction can cause many problems such as in-domain measurement and actuation and control spillover. This thesis attempts to investigate the problem of vibration control of nonclassical microscale beams using the partial differential equation control theory which eliminates spillover instabilities. To this...
Vibration Boundary Control in Micro-beams Equipped with a Layer of Piezoelectric Actuator
, M.Sc. Thesis Sharif University of Technology ; Salarieh, Hassan (Supervisor) ; Alasti, Aria (Supervisor) ; Vatankhah, Ramin ($item.subfieldsMap.e)
Abstract
Nowadays, micro systems in many area of science and technology have special importance and status. The main function of these systems is based on the deformation of a beam at micro scale. Therefore study of behavior and control of micro-beams will have a great importance. Among micro-beams, clamped-free and clamped-clamped micro beams that actuated by piezoelectric and electrostatic actuators have wider applications. For example, clamped-free micro-beams are used in atomic force microscopy (AFM), micro switches, mass sensors and micro-accelerometers and clamped-clamped micro-beams are used in micro mirrors and Grating Light Valves (GLV). In this thesis, the studied system is clamped-free...
Boundary Control of Vibration in Satellite Flexible Solar Panels
, M.Sc. Thesis Sharif University of Technology ; Alasty, Aria (Supervisor) ; Salarieh, Hassan (Supervisor) ; Vatankhah, Ramin (Co-Advisor)
Abstract
Many spacecrafts and satellites have long flexible components, the most common ones are the satellites with flexible solar panels, which are used to provide the satellite energy. The governing equations of the satellite rigid motion along with the solar panels vibrations are the combination of the coupled partial and ordinary differential equations. Various reasons, such as the satellite maneuvers and the external disturbances, cause the vibration of panels. Due to the dependence between the governing equations of the satellite rigid motion and the flexible components vibrations, these vibrations affect the satellite rigid dynamics and the control aims; therefore, in addition to the...
Design and Simulation of a Passive Microfluidic Device for Particle Separation
, M.Sc. Thesis Sharif University of Technology ; Shamloo, Amir (Supervisor)
Abstract
Nowadays, separation and filtration of particles has many industrial applications in biology and medicine. In this thesis, passive microfluidics are designed and simulated which are able to separate and filter particles. Although particles aer generally expected to follow laminar flow streamlines in the absence of external forces, inertial forxes van cause particles to migrate across mictochannels in an accurate and predictable manner. The effect of these forces is invedtigated, and by using previous research, a model is developed to predict these forces. First design is a microchannel with Archimedean spiral which utilizes both inertial forces and Dean flow to separate particles in the...
Formulation for Mechanical Modelling of Small-Scale Micro- and Nano- Beams and Plates for Statical and Vibrational Analysis Based on the Second Strain Gradient Theory
, Ph.D. Dissertation Sharif University of Technology ; Asghari, Mohsen (Supervisor) ; Vatankhah, Ramin (Co-Advisor)
Abstract
In this thesis, the formulation of beams and plates in the micro- and nano scales is presented based on the second strain gradient theory (SSGT) introduced by Mindlin. The SSGT is a non-classical continuum theory that includes the second-order gradients of strain tensor in its formulation and this leads to more accurate modeling for mechanical behavior of materials than the strain gradient theory. On the other hand, due to the ever-increasing use of micro- and nano-electromechanical systems, analysis of the mechanical behavior of their deformable components for design and construction is of particular importance. For this purpose, analysis of Timoshenko beams and Euler-bernoulli beams made...
Performance of RC Shear Walls Strengthened by Vertical Strips of Steel Plates under Seismic Loading
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor)
Abstract
Even though a considerable amount of research has been conducted on composite wall system during past years, very limited research has been reported on shear walls strengthened by steel plates. In 2008, the composite shear wall, which consisted of reinforced concrete wall, retrofitted by steel plates, attached to both sides of RC walls using mechanical connectors in form of shear studs, bolts or lateral ties tested under axial load and lateral force. In this research, seismic behavior of RC shear walls strengthened by vertical strips of steel plates is going to be studied. The result will be compared with RC shear wall which fully covered by steel plates. The behavior of RC shear wall will...
Large-scale changes of the cloud coverage in the ϵ Indi Ba and Bb system
, Article Monthly Notices of the Royal Astronomical Society ; Volume 495, Issue 4 , May , 2021 , Pages 3881-3899 ; 00358711 (ISSN) ; Helling, Ch ; Scholz, A ; Hodosan, G ; Dominik, M ; Hundertmark, M ; Jørgensen, U. G ; Longa Peña, P ; Sajadian, S ; Skottfelt, J ; Snodgrass, C ; Bozza, V ; Burgdorf, M. J ; Campbell White, J ; Jaimes, R. F ; Fujii, Y. I ; Haikala, L. K ; Henning, T ; Hinse, T. C ; Lowry, S ; Mancini, L ; Rahvar, S ; Rabus, M ; Southworth, J ; Von Essen, C ; The MiNDSTEp Collaboration ; Sharif University of Technology
Oxford University Press
2021
Abstract
We present the results of 14 nights of I-band photometric monitoring of the nearby brown dwarf binary, ϵ Indi Ba and Bb. Observations were acquired over 2 months, with a total of close to 42 h of coverage at a typically high cadence of 1.4 min. At a separation of just 0.7 arcsec, we do not resolve the individual components, and so effectively treat the binary as if it were a single object. However, ϵ Indi Ba (spectral type T1) is the brightest known T-type brown dwarf, and is expected to dominate the photometric signal. We typically find no strong variability associated with the target during each individual night of observing, but see significant changes in mean brightness – by as much as...
Effect of cooling rate on microstructure and mechanical properties of gray cast iron
, Article Materials Science and Engineering A ; Volume 528, Issue 2 , 2010 , Pages 583-588 ; 09215093 (ISSN) ; Davami, P ; Varahram, N ; Sharif University of Technology
2010
Abstract
This paper presents the results obtained and the deductions made from a series of microstructural studies and mechanical tests involving gray cast iron which was sand cast using a variety of modules. The effect of cooling rate on the primary dendrite arm spacing (DAS), secondary dendrite arm spacing (SDAS), thickness of ferrite-cementite layer (λe) and the hardness (HB) were evaluated. Results show that the both DAS and SDAS and also λe are highly dependent on the cooling rate, and they decreases as the cooling rate increases. More attempts were also done to correlate the HB with DAS, SDAS and λe. It was found that HB increases as DAS, SDAS and λe decreases
3-D simulation of mold filling with κ-ε turbulence modeling
, Article Proceedings of the 14th IASTED International Conference on Applied Simulation and Modelling, Benalmadena, 15 June 2005 through 17 June 2005 ; 2005 , Pages 437-442 ; 0889864691 (ISBN) ; Babaei, R ; Asgary, K ; Davami, P ; Hamza M. H ; Sharif University of Technology
2005
Abstract
In this work the SOLA-VOF method was used to solve the Navier-Stokes equations and track the free surface. For modeling the turbulence phenomena in the mold filling κ-ε model was used. In this method solving domain was discreted to three regions includes: laminar sub layer, boundary layer and internal region. The simulation results were shown to be in a good agreement with the experimental results
Effect of η phase on mechanical properties of the iron-based superalloy using shear punch testing
, Article ISIJ International ; Volume 53, Issue 2 , 2013 , Pages 311-316 ; 09151559 (ISSN) ; Kheirandish, S ; Razavi, S. H ; Abbasi, S. M ; Sahrapour, P ; Sharif University of Technology
2013
Abstract
In this paper, the shear deformation behavior of A286 Iron-based superalloy was studied with an emphasis on the influence of η phase on shear strength. The η (Ni3Ti phase precipitates at high temperature heat treatment or during services at the expense of gamma prime phase. According to the microstructural features, no evidences of η phase were found at 650 and 720°C. η phase precipitated at 780 and 840°C and the amount of it increased with an increase the time and temperature. Because of using the alloy as fasteners, investigation of shear properties and the influence of η phase on it are indispensable. The shear strength of the alloy with different volume fractions of η was examined. It...
A new imidazole-containing imidazolidinone catalyst for organocatalyzed asymmetric conjugate addition of nitroalkanes to aldehydes
, Article Advanced Synthesis and Catalysis ; Volume 349, Issue 4-5 , 2007 , Pages 740-748 ; 16154150 (ISSN) ; Hartikka, A ; Matloubi Moghaddam, F ; Arvidsson, P. I ; Sharif University of Technology
Wiley-VCH Verlag
2007
Abstract
Herein we report a new organocatalyst for the asymmetric Michael addition of nitroalkanes to α,β-unsaturated aldehydes. This catalyst incorporates a basic imidazole group in addition to the secondary amine responsible for activation of the α,β-unsaturated carbonyl compounds via iminium ion formation. The new organocatalyst is capable of catalyzing the enantioselective carbon-carbon bond formation with a high degree of enantiocontrol providing products in enantiomeric excesses of up to 92% and yields of up to to 91 %. These results constitute the best results so far reported for organocatalyzed Michael additions of nitroalkanes to α,β-unsaturated aldehydes, and provide proof of principle that...
A tandem aldol-diels-alder reaction accelerated in water: An approach to the catalyst-free one-pot synthesis of spiro thio-oxindoles
, Article Journal of the Iranian Chemical Society ; Volume 7, Issue 3 , September , 2010 , Pages 781-790 ; 1735207X (ISSN) ; Hojabri, L ; Taheri, S ; Pirani, P ; Sharif University of Technology
2010
Abstract
Spiro thio-oxindoles are prepared in situ by the reaction of the corresponding aldehydes and thio-oxindoles in a straightforward, environmentally friendly, highly efficient and simple procedure. The reaction took place in water with no catalyst added. This one-pot reaction afforded regio- and diastereoselective products in high yields (61-93%)
A large dataset of white blood cells containing cell locations and types, along with segmented nuclei and cytoplasm
, Article Scientific Reports ; Volume 12, Issue 1 , 2022 ; 20452322 (ISSN) ; Saghari, S ; Tavakoli, S ; Rostami, P ; Abaszadeh, M ; Mirzadeh, F ; Satlsar, E. S ; Gheidishahran, M ; Gorgi, F ; Mohammadi, S ; Hosseini, R ; Sharif University of Technology
Nature Research
2022
Abstract
Accurate and early detection of anomalies in peripheral white blood cells plays a crucial role in the evaluation of well-being in individuals and the diagnosis and prognosis of hematologic diseases. For example, some blood disorders and immune system-related diseases are diagnosed by the differential count of white blood cells, which is one of the common laboratory tests. Data is one of the most important ingredients in the development and testing of many commercial and successful automatic or semi-automatic systems. To this end, this study introduces a free access dataset of normal peripheral white blood cells called Raabin-WBC containing about 40,000 images of white blood cells and color...
Methods to Derive the Differential Equation of the Free Surface Boundary
, Article Ground Water ; Volume 49, Issue 2 , 2011 , Pages 133-143 ; 0017467X (ISSN) ; Neuman, S. P ; Strack, O. D. L ; Verruijt, A ; Jamali, M ; Seymour, B ; Bear, J ; Cheng, A. H. D ; Chen, C ; Kuang, X ; Jiao, J. J ; Sharif University of Technology
2011
Study and production of silicone rubber and polyethylene alloy
, Article Journal of Thermoplastic Composite Materials ; Volume 24, Issue 5 , 2011 , Pages 669-677 ; 08927057 (ISSN) ; Meibod, M. P ; Frounchi, M ; Dadbin, S ; Sharif University of Technology
2011
Abstract
Linear silicone rubber and polyethylene alloy produced from extrusion-injecting process will be present in separate phases. While samples are mixed with 1% dicumylperoxide, DCP, and injected in extruder, an alloy is almost formed. In addition, when the samples containing silicon rubber with vinyl group are mixed with polyethylene and passed in the vicinity of electron beam, a similar reaction occurs, as confirmed from FTIR spectrum. The water contact angles for the samples has been listed in the article. Furthermore, the crystallinity of samples produced via electron beam method is more than that obtained from peroxide method. On the other hand, the tensile strengths of produced samples via...
Grafting the sol-gel based sorbents by diazonium salts: A novel approach toward unbreakable capillary microextraction
, Article Journal of Chromatography A ; Volume 1318 , November , 2013 , Pages 58-64 ; 00219673 (ISSN) ; Bayat, P ; Piri Moghadam, H ; Sharif University of Technology
2013
Abstract
The present work deals with a novel approach for grafting a sol-gel based sorbent, using diazonium salts for preparation of an unbreakable capillary microextraction (CME) device in on-line combination with high performance liquid chromatography (HPLC). The use of diazonium salts modifier allowed all types of metallic and non-metallic substrates to be used without any limitation. Substrates including copper, brass, stainless steel and polytetrafluoroethylene (PTFE) were chosen to be functionalized by chemical or electrochemical reduction of 4-amino phenyl acetic acid. Then, 3-(trimethoxysilyl)propylamine (3TMSPA) was selected as the precursor and the only reagent for preparation of the...
A 38 pJ/b optimal soft-MIMO detector
, Article IEEE Transactions on Circuits and Systems II: Express Briefs ; Volume 64, Issue 9 , 2017 , Pages 1062-1066 ; 15497747 (ISSN) ; Doostnejad, R ; Mahdavi, M ; Gulak, P. G ; Sharif University of Technology
2017
Abstract
An optimal soft multiple-input multiple-output (MIMO) detector is proposed with linear complexity for a general spatial multiplexing system with two transmitting symbols and NR 2 receiving antennas. The computational complexity of the proposed scheme is independent of the operating signal-to-noise ratio and grows linearly with the constellation order. It provides the soft maximum-likelihood solution using an efficient log-likelihood ratio calculation method, avoiding the exhaustive search on all the candidate nodes. Moreover, an efficient pipelined hardware implementation of the detection algorithm is proposed, which is fabricated and fully tested in a 130-nm CMOS technology. Operating at...