Loading...
Search for:
rezayat--e
0.105 seconds
Total 2363 records
Ultrasound dosimetery using microbubbles
, Article IFMBE Proceedings, 20 June 2011 through 23 June 2011 ; Volume 35 IFMBE , June , 2011 , Pages 359-362 ; 16800737 (ISSN) ; 9783642217289 (ISBN) ; Zahedi, E ; Tavakkoli, J ; Sharif University of Technology
2011
Abstract
In this paper, a new technique based on nonlinear resonance of microbubbles is investigated in order to estimate the amplitude of an ultrasound wave pressure field. First, the existing theoretical model is reviewed. Then, an experimental setup consisting of a bubble generator and transmitting/receiving ultrasound transducers operating in the 1 MHz frequency range is described. The effect of background noise is also taken into account. Results show that the second harmonic oscillations are detectable, paving the way to develop a quantitative method for in vivo calibration of ultrasound waves
High-speed imaging database of water jet disintegration Part II: Temporal analysis of the primary breakup
, Article International Journal of Multiphase Flow ; Volume 145 , 2021 ; 03019322 (ISSN) ; Farshchi, M ; Berrocal, E ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
This paper is Part II of a series of articles focusing on the disintegration of a cylindrical (Ø=0.60 mm diameter) water jet in a quiescent atmosphere, from Rayleigh to early atomization breakup regimes. Liquid fluorescence high-speed imaging is used here, instead of shadowgraphy, providing a more faithful representation of liquid jet breakup dynamics as described in Part I (Roth et al., 2021). Using these data, the aim of this article is to perform a temporal analysis of the primary breakup process and to investigate the variation of breakup length in the time-domain, under each breakup regime. The results indicate that the liquid jet velocity at the onset of primary breakup oscillates...
Ultrasound Intensity Exposimetry in Physiotherapy Devices using Micro-Bubbles
, M.Sc. Thesis Sharif University of Technology ; Zahedi, Edmond (Supervisor)
Abstract
Routine ultrasound calibration methods have some restrictions such as: low bandwidth, low frequency resolution, limited spatial resolution, the high cost of test and risk of damage to the transducer when exposed to high powers. In this thesis, a new technique based on microbubble resonance is proposed. Non-linear resonating microbubbles produce harmonics;the first harmonic may be masked by reflection from larger microbubbles as well as unwanted reflections which cause ambiguity in the determination of the amplitude of the excited pressure. Therefore, the second harmonic is used, with a single characteristic peak. In order to model the physical phenomenon, the second harmonic generated in the...
Fabrication of aluminium matrix composites reinforced by submicrometre and nanosize Al 2O 3 via accumulative roll bonding
, Article Materials Science and Technology (United Kingdom) ; 2012 , Pages 1233-1240 ; 02670836 (ISSN) ; Akbarzadeh, A ; Sharif University of Technology
2012
Abstract
Aluminium matrix composites reinforced with submicrometre and nanosize Al 2O 3 particles were successfully manufactured in the form of sheets through eight cycles of accumulative roll bonding process. The mechanical properties of the produced composite are compared with accumulative roll bonded commercially pure aluminium. It is shown that only 1 vol.-% of submicrometre or nanosize alumina particles as reinforcement in the structure can significantly improve the yield and ultimate tensile strengths. Scanning electron microscopy revealed that particles have a random and uniform distribution in the matrix especially in the less volume fraction of alumina particles, and strong mechanical...
Bonding behavior of Al-Al2O3 laminations during roll bonding process
, Article Materials and Design ; Volume 36 , 2012 , Pages 874-879 ; 02641275 (ISSN) ; Akbarzadeh, A ; Sharif University of Technology
2012
Abstract
Accumulative roll bonding (ARB) is used as a novel method to produce particle reinforced metal matrix composites (MMCs). Roll bonding of the sheets with layers of powder on their surfaces is the main stage in this process and it has been found that quality of the bonding has an important role in properties of the product. In this work, the behavior of alumina particles layer at interface during the rolling is investigated and the effects of particle size and amount of particle at interface on bonding of the commercial pure aluminum sheets are also studied. The results of peeling test indicate that presence of the powder at interface reduces the bond strength. However, it is shown that by...
Theoretical model for evaluating the threshold reduction in roll bonding of Al/Al 2O 3/Al laminations
, Article Metals and Materials International ; Volume 18, Issue 5 , 2012 , Pages 827-832 ; 15989623 (ISSN) ; Akbarzadeh, A ; Sharif University of Technology
Springer
2012
Abstract
Roll bonding is the most important stage of the accumulative roll bonding process, which is used to produce high strength composites. The presence of a particle layer at the interface alters the bonding condition and increases the threshold reduction for the commencement of bonding. In this study, the bonding mechanism in presence of powder at the interface is analyzed and a theoretical model is proposed to predict the required threshold reduction in warm roll bonding of commercially pure aluminum sheets as a function of amount of alumina particles at the interface. The model considers the rolling parameters and the effect of amount and size of particles by defining some constants, which are...
Experimental Study on Primary Breakup Dynamics and Spray Characteristics of Rotary Atomizers
, Ph.D. Dissertation Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
The liquid breakup analysis and spray characteristics measurement of atomizers are very essential for the numerical modeling of the primary atomization in combustion chambers. The rotary atomizers are used in many applications especially in small gas turbine engines as a fuel injection system. An experimental investigation of primary breakup dynamics and spray characteristics of rotary atomizers with high aspect ratio discharge channels are described. Four different rotary atomizers with round radial, round radial-axial, round radial tangential, and square radial discharge channels are studied. The purposes of this study are to identify the effect of channel orientation and its geometry on...
Experimental Study on Liquid Breakup Process in Slinger Injection
, M.Sc. Thesis Sharif University of Technology ; Farshchi, Mohammad (Supervisor)
Abstract
In small turbojet engines, it is important to find a suitable fuel injector with good spray quality. However, the rotating fuel injection system can potentially provide high atomization quality without the high-pressure fuel pump through the centrifugal forces of the engine shaft. The spray characteristics of rotary atomization for small gas turbines can be investigated using a high-speed camera. To analyze the breakup process of the liquid column and liquid film, spray visualization tests should performed under varied test conditions.In this research, experimental study on liquid breakup process has performed in rotary atomizer of j402 turbojet engine with the name of slinger injector, to...
Investigation of the Effects of Various Parameters on Microstructure and Mechanical Properties of Nano-Composite Al-Al2O3 and Al-Sic Produced by Accumulative Roll Bonding
, M.Sc. Thesis Sharif University of Technology ; Akbarzadeh Changiz, Abbas (Supervisor)
Abstract
Accumulative roll bonding has been used as novel method to produce the composite with ultra fine grain microstructure. This method has two steps, impose the particles as reinforcement between the layers by roll bonding process and then distribute the particles in matrix and generat an ultra fine grain microstructure during the ARB passes. In the present work, ARB process was performed to produce the Al/SiC and Al/Al2O3 nano-composites with various particles size and different volume fraction of reinforcement. Microscopic observations such as OM, SEM and TEM and XRD analyses were used to investigate the microstructure of produced composites and the distribution of the particles in matrix...
Fabrication of high-strength al/sicp nanocomposite sheets by accumulative roll bonding
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 43, Issue 6 , 2012 , Pages 2085-2093 ; 10735623 (ISSN) ; Akbarzadeh, A ; Owhadi, A ; Sharif University of Technology
2012
Abstract
Accumulative roll bonding (ARB) was successfully used as a severe plastic deformation method to produce Al-SiC nanocomposite sheets. The effects of process pass and amount of SiC content on microstructure and mechanical properties of the composites are investigated. As expected, production of ultrafine grain structures by the ARB process as well as nanosize particulate reinforcements in the metal matrix composite (MMC) resulted in excellent mechanical properties. According to the results of the tensile tests, it is shown that the yield and tensile strengths of the composite sheet increased with the number of ARB cycles without saturation at the last cycles. Scanning electron microscopy (SEM)...
Production of high strength Al-Al 2O 3 composite by accumulative roll bonding
, Article Composites Part A: Applied Science and Manufacturing ; Volume 43, Issue 2 , February , 2012 , Pages 261-267 ; 1359835X (ISSN) ; Akbarzadeh, A ; Owhadi, A ; Sharif University of Technology
2012
Abstract
Recently accumulative roll bonding has been used as a novel method to produce particle reinforced metal matrix composites. In this study, aluminum matrix composite reinforced by submicron particulate alumina was successfully produced and the effects of number of ARB cycles and the amount of alumina content on the microstructure and mechanical properties of composites were investigated. According to the results of tensile tests, it is shown that the yield and tensile strengths of the composite are increased with the number of ARB cycles. Scanning electron microscopy (SEM) reveals that particles have a random and uniform distribution in the matrix by the ARB cycles and a strong mechanical...
Primary breakup dynamics and spray characteristics of a rotary atomizer with radial-axial discharge channels
, Article International Journal of Multiphase Flow ; Volume 111 , 2019 , Pages 315-338 ; 03019322 (ISSN) ; Farshchi, M ; Ghorbanhoseini, M ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
An experimental investigation of primary breakup dynamics and spray characteristics of a rotary atomizer with high aspect ratio radial-axial discharge channel is described. A high-resolution shadow imaging technique with pulsed backlight illumination was used for spray visualization. For the rotary atomizer with high aspect ratio discharge channel and radial-axial orientation, visualization showed the occurrence of Centripetal–Coriolis-induced stream-mode injection for all operating conditions. In this mode of injection, a crescent liquid film forms in the channel exit and issues from the orifice as a liquid column or a thin liquid sheet depending on atomizer operating conditions. It was...
Primary breakup dynamics and spray characteristics of a rotary atomizer with radial-axial discharge channels
, Article International Journal of Multiphase Flow ; 2018 ; 03019322 (ISSN) ; Farshchi, M ; Ghorbanhoseini, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
An experimental investigation of primary breakup dynamics and spray characteristics of a rotary atomizer with high aspect ratio radial-axial discharge channel is described. A high-resolution shadow imaging technique with pulsed backlight illumination was used for spray visualization. For the rotary atomizer with high aspect ratio discharge channel and radial-axial orientation, visualization showed the occurrence of Centripetal–Coriolis-induced stream-mode injection for all operating conditions. In this mode of injection, a crescent liquid film forms in the channel exit and issues from the orifice as a liquid column or a thin liquid sheet depending on atomizer operating conditions. It was...
Feasibility of infrared tracking of beating heart motion for robotic assisted beating heart surgery
, Article International Journal of Medical Robotics and Computer Assisted Surgery ; Volume 14, Issue 1 , February , 2018 ; 14785951 (ISSN) ; Farahmand, F ; Vossoughi, G ; Ghavidel, A. A ; Rezayat, M ; Sharif University of Technology
John Wiley and Sons Ltd
2018
Abstract
Background: Accurate tracking of the heart surface motion is a major requirement for robot assisted beating heart surgery. Method: The feasibility of a stereo infrared tracking system for measuring the free beating heart motion was investigated by experiments on a heart motion simulator, as well as model surgery on a dog. Results: Simulator experiments revealed a high tracking accuracy (81 μm root mean square error) when the capturing times were synchronized and the tracker pointed at the target from a 100 cm distance. The animal experiment revealed the applicability of the infrared tracker with passive markers in practical heart surgery conditions. Conclusion: With the current technology,...
Ceria reinforced nanocomposite solder foils fabricated by accumulative roll bonding process
, Article Journal of Materials Science: Materials in Electronics ; Volume 23, Issue 9 , September , 2012 , Pages 1698-1704 ; 09574522 (ISSN) ; Kokabi, A. H ; Miyashita, Y ; Mutoh, Y ; Rezayat, M ; Madaah Hosseini, H. R ; Sharif University of Technology
Springer
2012
Abstract
As one of the key technologies for high performance electronic devices, composite solders have been recently developed to improve thermal and mechanical properties of solder joints. In this study, accumulative roll bonding process was used as an effective alternative method for manufacturing high-strength, finely dispersed, void-free and highly uniform Sn-Ag-Cu/CeO 2 nanocomposite solders. Microstructural investigation of nanocomposite solders revealed that homogenous distribution of CeO 2 nanoparticle has been achieved and the eutectic as-cast morphology of the solder changed to recrystallized fine grained structure. As a result of severe plastic deformation during rolling, brittle and...
Chemotherapeutic effects of Apigenin in breast cancer: Preclinical evidence and molecular mechanisms; enhanced bioavailability by nanoparticles
, Article Biotechnology Reports ; Volume 34 , 2022 ; 2215017X (ISSN) ; Zahmatkeshan, M ; Akbarzadeh, A ; Rabiee, N ; Ahmadi, S ; Keyhanvar, P ; Rezayat, S. M ; Seifalian, A. M ; Sharif University of Technology
Elsevier B.V
2022
Abstract
This review highlights using nanotechnology in increasing the bioavailability of AP (Apigenin) to enhance its therapeutic efficacy in breast cancer treatment. Breast cancer is one of the most leading causes of cancer death in women both in developed and developing countries. According to several epidemiological and clinical trial studies that indicate progestin-stimulated breast cancer in post-menopausal women; it is necessary to determine compounds to suppress or attenuate the tumor-promoting effects of progestins in breast cells. For this purpose, using the natural anti-progestins, including AP compared with the chemical ones could be significantly effective due to the lack of toxicities...
Dose-dependent effects of nanoscale graphene oxide on reproduction capability of mammals
, Article Carbon ; Volume 95 , December , 2015 , Pages 309-317 ; 00086223 (ISSN) ; Ghaderi, E ; Hashemi, E ; Akbari, E ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
In vivo dose-dependent effects of nanoscale graphene oxide (NGO) sheets on reproduction capability of Balb/C mice were investigated. Biodistribution study of the NGO sheets (intravenously injected into male mice at dose of ∼2000 μg/mL or 4 mg/kg of body weight) showed a high graphene uptake in testis. Hence, in vivo effects of the NGO sheets on important characteristics of spermatozoa (including their viability, morphology, kinetics, DNA damage and chromosomal aberration) were evaluated. Significant in vivo effects was found at the injected concentrations ≥200 μg/mL after (e.g., ∼45% reduction in sperm viability and motility at 2000 μg/mL). Observation of remarkable DNA fragmentations and...
Accelerated differentiation of neural stem cells into neurons on ginseng-reduced graphene oxide sheets
, Article Carbon ; Volume 66 , January , 2014 , Pages 395-406 ; Ghaderi, E ; Abouei, E ; Hatamie, S ; Ghasemi, E ; Sharif University of Technology
2014
Abstract
Asian red ginseng was used for green reduction of chemically exfoliated graphene oxide (GO) into reduced graphene oxide (rGO). The reduction level and electrical conductivity of the ginseng-rGO sheets were comparable to those of hydrazine-rGO ones. Reduction by ginseng resulted in repairing the sp 2 graphitic structure of the rGO, while hydrazine-rGO showed more defects and/or smaller aromatic domains. The ginseng-rGO sheets presented a better stability against aggregation than the hydrazine-rGO ones in an aqueous suspension. Whilst the hydrophobic hydrazine-rGO films exhibited no toxicity against human neural stem cells (hNSCs), the hydrophilic GO and ginseng-rGO films (as more...
Contested framings and policy controversies: Analysing biosafety policy-making in Iran
, Article Science and Public Policy ; Volume 40, Issue 5 , 2013 , Pages 616-627 ; 03023427 (ISSN) ; Millstone, E ; Sharif University of Technology
2013
Abstract
Vigorous debates have taken place within and between many countries about regulatory policy regimes covering the assessment and approval of genetically modified (GM) crops. In Iran, a very vigorous and hotly contested policy debate concerning legislation covering GM crops occurred between 2004 and 2009, but it was confined within government circles with almost no public discussion. This paper analyses the Iranian policy-making process in the period 2006-9. It explains how and why a stalemate arose in disputes between ministries and departments. The chosen analytical framework draws mainly on the regulation of technological risks and the analysis of public policy-making. It deploys the...
On the possible volumes of μ-way latin trades
, Article Aequationes Mathematicae ; Volume 63, Issue 3 , 2002 , Pages 303-320 ; 00019054 (ISSN) ; Billington, E. J ; Bryant, D. E ; Mahmoodian, E. S ; Sharif University of Technology
Birkhauser Verlag Basel
2002
Abstract
A μ-way latin trade of volume s is a set of μ partial latin rectangles (of inconsequential size) containing exactly the same s filled cells, such that if cell (i, j) is filled, it contains a different entry in each of the μ partial latin rectangles, and such that row i in each of the μ partial latin rectangles contains, set-wise, the same symbols and column j, likewise. In this paper we show that all μ-way latin trades with sufficiently large volumes exist, and state some theorems on the non-existence of μ-way latin trades of certain volumes. We also find the set of possible volumes (that is, the volume spectrum) of μ-way latin trades for μ = 4 and 5. (The case μ = 2 was dealt with by Fu,...