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Geometrically modified einzel lenses, from the conventional cylindrical einzel lens to cubic and continuous einzel lens
, Article IEEE Transactions on Plasma Science ; Volume 45, Issue 5 , 2017 , Pages 828-835 ; 00933813 (ISSN) ; Yasrebi, N ; Monjezi, H ; Rashidian, B ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
New geometrical counterparts to the conventional Einzel lens, cubic, and the continuous body electrostatic (CBE) lenses are introduced and their performances are investigated in terms of different aberrations and input beam properties. Design curves for the continuous body electrostatic lens are presented. Relative sensitivity is proposed as a figure of merit, based on which the focusing characteristics of the two new lenses are compared with that of a conventional Einzel, and a quadrupole lenses of the same size, as well. Moreover, performance and characteristics of the lenses are compared in terms of their corresponding sensitivities to the applied voltage and the incidence beam...
Microstructural analysis of a girth welded subsea pipe
, Article Engineering Letters ; Volume 26, Issue 1 , 2018 , Pages 193-202 ; 1816093X (ISSN) ; Wang, B ; Wrobel, L. C ; Chizari, M ; Sharif University of Technology
International Association of Engineers
2018
Abstract
This research focuses on simulation of the dissimilar materials’ welding, stainless steel and mild steel, using finite element and experiment to enhance the method and better understand the transient temperature profiles and the stress distribution in a cladded pipe. The microstructural come as fenestrated and the computer results show that the temperature distribution in the modelled pipe is a function of the thermal conductivity of each weld metal as well as the distance away from the heat source. © 2018, International Association of Engineers. All rights reserved
Inertial particle focusing in serpentine channels on a centrifugal platform
, Article Physics of Fluids ; Volume 30, Issue 1 , 2018 ; 10706631 (ISSN) ; Mashhadian, A ; Sharif University of Technology
American Institute of Physics Inc
2018
Abstract
Inertial particle focusing as a powerful passive method is widely used in diagnostic test devices. It is common to use a curved channel in this approach to achieve particle focusing through balancing of the secondary flow drag force and the inertial lift force. Here, we present a focusing device on a disk based on the interaction of secondary flow drag force, inertial lift force, and centrifugal forces to focus particles. By choosing a channel whose cross section has a low aspect ratio, the mixing effect of the secondary flow becomes negligible. To calculate inertial lift force, which is exerted on the particle from the fluid, the interaction between the fluid and particle is investigated...
A novel algorithm for fast and efficient multifocus wavefront shaping
, Article Photons Plus Ultrasound: Imaging and Sensing 2018, 28 January 2018 through 1 February 2018 ; Volume 10494 , 2018 ; 16057422 (ISSN); 9781510614734 (ISBN) ; Nasiriavanaki, M ; Sharif University of Technology
SPIE
2018
Abstract
Wavefront shaping using spatial light modulator (SLM) is a popular method for focusing light through a turbid media, such as biological tissues. Usually, in iterative optimization methods, due to the very large number of pixels in SLM, larger pixels are formed, bins, and the phase value of the bins are changed to obtain an optimum phase map, hence a focus. In this study an efficient optimization algorithm is proposed to obtain an arbitrary map of focus utilizing all the SLM pixels or small bin sizes. The application of such methodology in dermatology, hair removal in particular, is explored and discussed. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only
Rubber-toughened epoxies: A critical review
, Article Polymer Reviews ; Volume 49, Issue 3 , 2009 , Pages 201-225 ; 15583724 (ISSN) ; Marouf, B. T ; Pearson, R. A
2009
Abstract
Epoxy resins have been used as structural materials since the late 1940s. Despite their desirable properties such as high strength, excellent creep resistance, and good adhesion, they suffer from low fracture energy. Rubber modification as a major toughening approach to overcome the inherent brittleness of epoxy polymers was introduced during the early 1970s. Since then, a large number of investigations have been conducted to elucidate different aspects of rubber-toughened epoxies. The present work is a critical review of the field focusing on the important parameters affecting rubber-toughening. The studies reviewed are classified in five categories including roles of matrix ductility,...
High intensity focused ultrasound (HIFU) ablation of porous liver: numerical analysis of heat transfer and hemodynamics
, Article Applied Thermal Engineering ; Volume 170 , April , 2020 ; Firoozabadi, B ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In the present study, the influence of the liver vascular bed on heat transfer in a tumor located close to the hepatic artery and exposed to high intensity focused ultrasound (HIFU), is studied numerically. For this purpose, an acoustics-thermal-fluid coupling model based on the porous media theory under the local thermal non-equilibrium assumption is used to calculate the temperature field in the tumor, porous liver, and the hepatic artery. Different generations of the liver vasculature including arterial branches, terminal arterial branches, terminal veins and venous branches are examined at different porosities (the volume fraction of the vasculature). It is found that the liver...
Effect of laser additive manufacturing parameters on hardness and geometry of Inconel 625 parts manufactured by direct laser metal deposition
, Article Optik ; Volume 249 , 2022 ; 00304026 (ISSN) ; Akbari, J ; Moradi, M ; Malekshahi Beiranvand, Z ; Sharif University of Technology
Elsevier GmbH
2022
Abstract
This research investigates the effect of process parameters on the geometry and properties of In625 parts, manufactured by the direct laser metal deposition (DLMD) process. For this purpose, eight parts, consisting of 5 layers on top of each other, were manufactured, and the effect of laser power, laser focal plane position, and scanning speed on the height, width, and surface smoothness of each of them was investigated using design of experiment (DOE). The experimental results showed that the height of the parts manufactured by 800 W/mm and 200 W/mm of energy density is 3.69 mm and 6.12 mm, respectively. The thickness of the parts manufactured by 80 W/mm and 200 W/mm of energy density is...
Numerical study of the effect of vascular bed on heat transfer during high intensity focused ultrasound (HIFU) ablation of the liver tumor
, Article Journal of Thermal Biology ; Volume 86 , 2019 ; 03064565 (ISSN) ; Firoozabadi, B ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
In this study, the influence of vascular bed comprising terminal arterial branches on heat transfer in a liver tumor exposed to high intensity focused ultrasound (HIFU) is studied numerically. Also, the effect of vascular density on temperature distribution is investigated. A coupled set of acoustics, thermal, and fluid models is used to calculate the temperature distribution in the liver. The numerical model is established based on the Westervelt and bioheat equations along with the Navier-Stokes equations. Moreover, the acoustic streaming effect is included with Newtonian and non-Newtonian flow assumptions. It is found that in a vascular bed comprising terminal arterial branches, the...
Analysis of the Ultrasonic Cavitation on the Cancer Tumors
, M.Sc. Thesis Sharif University of Technology ; Ahmadian, Mohammad Taghi (Supervisor) ; Fallah Rajabzadeh, Famida (Supervisor)
Abstract
A complete understanding of high-intensity focused ultrasound-induced temperature changes in tissue requires insight into all potential mechanisms for heat deposition. Applications of therapeutic ultrasound often utilize acoustic pressures capable of producing cavitation activity. Recognizing the ability of bubbles to transfer acoustic energy into heat generation, a study of the role bubbles play in tissue hyperthermia becomes necessary. These bubbles are typically less than 50μm.
This dissertation examines the contribution of bubbles and their motion to an enhanced eating effect observed in a tissue-mimicking phantom. A series of experiments established a lationship between bubble...
This dissertation examines the contribution of bubbles and their motion to an enhanced eating effect observed in a tissue-mimicking phantom. A series of experiments established a lationship between bubble...
Pattern of the Acoustic Wave Penetration Into Soft Tissue and the Related Heat Generation
, M.Sc. Thesis Sharif University of Technology ; Assempour, Ahmad (Supervisor) ; Ahmadian, Mohamad Taghi (Supervisor)
Abstract
nowadays Acoustic play an important role in the treatment of various diseases, especially cancer. in 2020 cancer has been the cause of death for more than 10 million patients. High intensity focused ultrasound is a non-invasive technique that used successfully to treat Malignant cancers like liver, pancreas and prostate. One of the major problems of using acoustic waves is the absorption of high frequency waves by the tissue before reaching the target area. in this study, a finite element model used to find the relation between frequency and acoustic pressure of transducer and focal region intensity. the results show, the maximum intensity in focal region linearly proportional to frequency...
Deposition of metallic molybdenum thin films on 304L steel substrate by SUT-PF
, Article Surface and Coatings Technology ; 2016 ; 02578972 (ISSN) ; Nazmabadi, M ; Vosoughi, N ; Sharif University of Technology
Elsevier B. V
Abstract
The present research work aims to employ plasma focus in order to deposit molybdenum (Mo) on the 304 stainless steel substrate. The processing parameters were shot numbers as well as the distance of substrate from the anode tip. Stereo, atom force microscopy (AFM) and field emission-scanning electron microscopy (FE-SEM) equipped with energy dispersive X-ray spectroscopy (EDS) were used to study the deposited coatings. Microhardness measurements were also performed on the coatings. Results indicated that the plasma focus can be successfully applied to deposit Mo anode on the stainless steel substrate. The coatings contained discrete pores with sizes varying by processing parameters. The...
Methods for failure analysis and diagnosis of millimeter-wave system-in-packages
, Article IEEE Transactions on Device and Materials Reliability ; Volume 17, Issue 2 , 2017 , Pages 371-380 ; 15304388 (ISSN) ; Tazlauanu, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
This paper presents a sequence of affordable methods applied to diagnose a millimeter-wave system-in-package. The module used in this paper is a 60 GHz transceiver with a waveguide interface, designed to transmit 8 dBm of saturated power. It consists of a flip-chipped RFIC, a multi-layer organic substrate, a metal enclosure with a standard waveguide interface, passive components and a 30-pin connector. The first measured output power was 3 to 6 dB below the desired value over the 60 GHz band. Thus, all parts of the module were thoroughly investigated to detect the cause of power drop. By 3-D electromagnetic simulation of the enclosure, the cavity modes and power leakage in the enclosure were...
Effect of angular position on the quality of dense plasma focus-based additive layer manufactured molybdenum coatings
, Article International Journal of Advanced Manufacturing Technology ; Volume 99, Issue 9-12 , 2018 , Pages 2717-2725 ; 02683768 (ISSN) ; Hosseinzadeh, A ; Nazmabadi, M ; Vosoughi, N ; Sharif University of Technology
Springer London
2018
Abstract
The present research aims at depositing molybdenum on stainless steel substrate using dense plasma focus (DPF) device. The varying parameter was the angular position of substrate surface from the anode tip. The deposited layers were characterized using various analyses such as X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and microhardness measurements. Microstructural observations revealed that the deposited coatings had rough surfaces containing holes as well as a stripe-featured structure covering the whole surface including the interior regions of the holes and the regions among them....
The effects of anxiety and external attentional focus on postural control in patients with Parkinson’s disease
, Article PLoS ONE ; Volume 13, Issue 2 , 2018 ; 19326203 (ISSN) ; Azad, A ; Mehdizadeh, H ; Habibi, S. A ; Mandehgary Najafabadi, M ; Saberi, Z. S ; Rahimzadegan, H ; Moradi, S ; Behzadipour, S ; Parnianpour, M ; Taghizadeh, G ; Khalaf, K ; Sharif University of Technology
Public Library of Science
2018
Abstract
Background Although anxiety is a common non-motor outcome of Parkinson's disease (PD) affecting 40% of patients, little attention has been paid so far to its effects on balance impairment and postural control. Improvement of postural control through focusing on the environment (i.e. external focus) has been reported, but the role of anxiety, as a confounding variable, remains unclear. Objectives This study aimed to investigate the influence of anxiety and attentional focus instruction on the standing postural control of PD patients. Methods Thirty-four patients with PD (17 with high anxiety (HA-PD) and 17 with low anxiety (LA-PD)), as well as 17 gender- and age-matched healthy control...
A mixture of vortex terahertz radiation generation in inhomogeneous plasma by considering pump depletion
, Article Laser Physics ; Volume 29, Issue 1 , 2019 ; 1054660X (ISSN) ; Bahrampour, A. R ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
An attempt to extend helical terahertz radiation generation based on pump depletion is presented here. By considering an upward plasma density ramp, such a reasonable extension is examined to improve the results. It is claimed that the output terahertz energy is saturated which is attributed to laser pump divergence. The saturation effect is enhanced by considering suitable laser and plasma parameters. The adjustable slope of the density ramp is an important parameter for tuning terahertz generation effciency, which is restricted to the up and down limit. For the resonant excitation of terahertz radiation, the ripple wave number is suitably chosen to satisfy the phase matching condition....
A mixture of vortex terahertz radiation generation in inhomogeneous plasma by considering pump depletion
, Article Laser Physics ; Volume 29, Issue 1 , 2019 ; 1054660X (ISSN) ; Bahrampour, A. R ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
An attempt to extend helical terahertz radiation generation based on pump depletion is presented here. By considering an upward plasma density ramp, such a reasonable extension is examined to improve the results. It is claimed that the output terahertz energy is saturated which is attributed to laser pump divergence. The saturation effect is enhanced by considering suitable laser and plasma parameters. The adjustable slope of the density ramp is an important parameter for tuning terahertz generation effciency, which is restricted to the up and down limit. For the resonant excitation of terahertz radiation, the ripple wave number is suitably chosen to satisfy the phase matching condition....
An interface–particle interaction approach for evaluation of the co-encapsulation efficiency of cells in a flow-focusing droplet generator
, Article Sensors (Switzerland) ; Volume 20, Issue 13 , 2020 , Pages 1-17 ; Saidi, M. S ; Ghadami, S ; Kashaninejad, N ; Sharif University of Technology
MDPI AG
2020
Abstract
Droplet-based microfluidics offers significant advantages, such as high throughput and scalability, making platforms based on this technology ideal candidates for point-of-care (POC) testing and clinical diagnosis. However, the efficiency of co-encapsulation in droplets is suboptimal, limiting the applicability of such platforms for the biosensing applications. The homogeneity of the bioanalytes in the droplets is an unsolved problem. While there is extensive literature on the experimental setups and active methods used to increase the efficiency of such platforms, passive techniques have received less attention, and their fundamentals have not been fully explored. Here, we develop a novel...
Super-resolution photoacoustic microscopy using structured-illumination
, Article IEEE Transactions on Medical Imaging ; Volume 40, Issue 9 , 2021 , Pages 2197-2207 ; 02780062 (ISSN) ; Mostafavi, M ; Chen, J ; Kavehvash, Z ; Zhu, J ; Wang, L ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
A novel super-resolution volumetric photoacoustic microscopy, based on the theory of structured-illumination, is proposed in this paper. The structured-illumination will be introduced in order to surpass the diffraction limit in a photoacoustic microscopy (PAM) structure. Through optical excitation of the targeted object with a sinusoidal spatial fringe pattern, the object's frequency spectrum is forced to shift in the spatial frequency domain. The shifting in the desired direction leads to the passage of the high-frequency contents of the object through the passband of the acoustic diffraction frequency response. Finally, combining the low-frequency image with the high-frequency parts in...
Investigating the effects of precursor concentration and gelling parameters on droplet-based generation of Ca-Alginate microgels: identifying new stable modes of droplet formation
, Article Materials Today Chemistry ; Volume 24 , 2022 ; 24685194 (ISSN) ; Rezaeian, M ; Mahmoudi, Z ; Shamloo, A ; Kazemzadeh Hannani, S ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Droplet-based microfluidics is an attractive approach for producing microgels due to its high potential to control the size and shape of the particles and precisely entrap the substances within the hydrogel matrix. However, the microfluidic generation of monodisperse microgels with desired structures is still challenging. Indeed, the rheological and interfacial properties of the immiscible fluids, as well as the adopted gelling strategy, play important roles in microfluidic methods. Herein, sodium alginate droplets with different concentrations are generated via a microfluidic device with a flow-focusing unit. Besides, a combined in situ and ex situ strategy is optimized to crosslink sodium...
Investigation of the different parameters contributing to bubble sticking inside physiological bifurcations
, Article Medical and Biological Engineering and Computing ; Volume 60, Issue 2 , 2022 , Pages 599-618 ; 01400118 (ISSN) ; Saidi, M. S ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
Gas embolotherapy (GE) is a developing medical method which can be utilized either as an autonomous therapeutic method to treat vascularized solid tumors, or it can be combined with other medical procedures—such as high-intensity focused ultrasound—to improve their efficiency. This paper is dedicated to investigating the different parameters which influence bubble lodging inside human vasculature via 2D-modeling of bubble dynamics in arteries’ and arterioles’ bifurcations which are potential sticking positions. Values used in the simulations are in accordance with the non-dimensional physiological numbers. It is found out that inlet pressure plays a decisive role in bubble lodging; the lower...