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jafarzadeh-esfehani--r
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Telemedicine and computer-based technologies during coronavirus disease 2019 infection; a chance to educate and diagnose
, Article Archives of Iranian Medicine ; Volume 23, Issue 8 , 2020 , Pages 561-563 ; Mirzaei Fard, M ; Habibi Hatam Ghale, F ; Rezaei Kalat, A ; Fathi, A ; Shariati, M ; Sadr Nabavi, A ; Miri, R ; Bidkhori, H. R ; Aelami, M. H ; Sharif University of Technology
Academy of Medical Sciences of I.R. Iran
2020
Abstract
Coronavirus disease 2019 (COVID-19) is now of global concern due to its rapid dissemination across the globe. The rapid spread of this viral infection, along with many of its unknown aspects, has posed new challenges to the health care systems. The main challenging effects of COVID-19 are rapid dissemination through close contact and varying clinical severity among different individuals. Furthermore, the medical staff in endemic areas are becoming exhausted and deal with a considerable level of job burnout, which can negatively affect their medical decision making. Also, due to the variable pulmonary manifestations of COVID-19, some physicians may misdiagnose patients. To overcome these...
Numerical simulation of interaction of mode-coupling and regenerative chatter in machining
, Article Journal of Manufacturing Processes ; Volume 27 , 2017 , Pages 252-260 ; 15266125 (ISSN) ; Movahhedy, M. R ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
Chatter vibration is a major obstacle in achieving high performance machining. In order to present a realistic model of chatter vibration, in this research, a finite element simulation of orthogonal chip formation combined with a 2D model of machine tool dynamics is developed. The proposed approach has the ability to incorporate various, mostly nonlinear, phenomena affecting chatter occurrence. The dynamic allows the tool to vibrate as a result of chip load variation leading to chatter. The 2DOF model makes it possible to observe the occurrence of model coupling phenomenon, in addition to the regeneration of waviness mechanism. The investigation of mode-coupling and regeneration phenomena in...
Plant-wide Control of an Integrated SOFC Plant with Direct Thermal Coupling Scheme
, M.Sc. Thesis Sharif University of Technology ; Pishvaie, Mahmoud Reza (Supervisor)
Abstract
Fuel cells are considered as one of the most promising for production of efficient and low-polluting electrical power. Hence, they can be a suitable alternative for fossil fuel sources. The solid oxide fuel cell (SOFC) is a direct conversion process, which works at high operating temperature (about 1000 °C). This high operating temperature makes them suitable for combining with gas turbines to achieve high overall fuel and power efficiency. A hybrid comportment consisting of an SOFC and a turbine (GT) is a multivariable nonlinear and strongly coupled system. On the other hand, total power generation in these systems which is a principal parameter should not be so sensitive to operating...
Collapse settlement of a clay core rockfill dam during the first impoundment
, Article 10th International Conference on Civil, Structural and Environmental Engineering Computing, Civil-Comp 2005, Rome, 30 August 2005 through 2 September 2005 ; 2005 ; 1905088000 (ISBN); 9781905088003 (ISBN) ; Heidari, T ; Azami, A. R ; Sharif University of Technology
2005
Abstract
In this paper the effects of the first reservoir filling on rockfill dams were studied numerically. To simulate the problem a simplified coupled formulation based on Biot's theory associated with unsaturated soils was presented. The finite element method was applied to the governing equations for the spatial discretization, followed by a generalized Newmark scheme used for the time domain discretization. The three effects of reservoir filling, collapse settlement produced by wetting the rockfill, water load on the dam body and buoyancy in the upstream shell were introduced. The nature of collapse settlement and how to numerically capture that by using the proper constitutive model is...
Sulfide stress corrosion cracking and hydrogen induced cracking of A216-WCC wellhead flow control valve body
, Article Case Studies in Engineering Failure Analysis ; Volume 1, Issue 3 , 2013 , Pages 223-234 ; 22132902 (ISSN) ; Kokabi, A. H ; Nasr Esfehani, M ; Sharif University of Technology
2013
Abstract
The wellhead flow control valve bodies which are the focal point of this failure case study were installed in some of the upstream facilities of Khangiran's sour gas wells. These valve bodies have been operating satisfactorily for 3 years in wet H2S environment before some pits and cracks were detected in all of them during the periodical technical inspections. One failed valve body was investigated by chemical and microstructural analytical techniques to find out the failure cause and provide preventive measures. The valve body alloy was A216-WCC cast carbon steel. During investigation many cracks were observed on the inner surface of the valve body grown from the surface pits. The results...
Prediction of machining chatter in milling based on dynamic FEM simulations of chip formation
, Article Advances in Manufacturing ; Volume 6, Issue 3 , 2018 , Pages 334-344 ; 20953127 (ISSN) ; Movahhedy, M. R ; Khodaygan, S ; Ghorbani, M ; Sharif University of Technology
Shanghai University Press
2018
Abstract
Chatter vibration is a major obstacle in achieveing increased machining performance. In this research, a finite element model of chip formation in a 2D milling process is used to predict the occurrence of chatter vibrations, and to investigate the effects of various machining parameters on this phenomenon. The dynamic properties of the machine tool at the tool tip are obtained based on experimental modal analysis, and are used in the model as the cutter dynamics. The model allows for the natural development of vibration as the result of the chip-tool engagement, and accounts for various phenomena that occur at the chip-tool interface ultimately leading to stable or unstable cutting. The...
Dynamic compaction method in physical model tests
, Article Scientia Iranica ; Volume 13, Issue 2 , 2006 , Pages 187-192 ; 10263098 (ISSN) ; Sharif University of Technology
Sharif University of Technology
2006
Abstract
In this paper, physical modeling tests are conducted to study some aspects of the dynamic compaction method. The loose models are prepared with dry sand. Four cylindrical tampers with different weight and cross section areas are used for compaction of the models and dropped from various heights. Strain gage type total stress measuring sensors are placed at different levels inside the model to measure the transferred vertical stresses due to collision of the tamper with the surface of the models. The typical stress time histories are presented. Improvement depth and crater depth and diameter created on the model surface are studied, among the various parameters affecting the phenomena. Using...
3D response of the Masjed-Soleyman rockfill dam during strong motions
, Article International Journal on Hydropower and Dams ; Volume 12, Issue 2 , 2005 , Pages 84- ; 13522523 (ISSN) ; Sharif University of Technology
2005
Vibration isolation of foundations subjected to impact loads by open trenches using physical models
, Article 16th International Conference on Soil Mechanics and Geotechnical Engineering: Geotechnology in Harmony with the Global Environment, ICSMGE 2005, Osaka, 12 September 2005 through 16 September 2005 ; Volume 3 , 2005 , Pages 1497-1500 ; 9059660285 (ISBN); 9789059660281 (ISBN) ; Sharif University of Technology
2005
Abstract
Surface waves generated during vibration of machine foundations are sometimes troublemaking and cause some damages to the nearby sensitive structures or people. Considering the function of the machines located on the foundations the dynamic loading could be harmonic or impact type. The main part of the generated energy is transferred to the ground by Rayleigh surface waves. One of the most reliable and economic methods for reduction of the effects of these generated waves is using open trenches around the dynamic sources, so called active isolation in literature. In this paper applicability and affecting parameters of the open trenches around the impact dynamic source is studied using...
Metabolomics fingerprinting of the human seminal plasma of asthenozoospermic patients
, Article Molecular Reproduction and Development ; Vol. 81, Issue. 1 , 2014 , pp. 84-86 ; ISSN: 1098-2795 ; Moazeni-Pourasil, R. S ; Jafarzadeh, N ; Savadi-Shiraz, E ; Sharif University of Technology
2014
Abstract
It is estimated that 20% of couples are infertile, and half of these infertility cases are linked to men. One of conditions that can affect male fertility is asthenozoospermia. We applied Raman spectroscopy to the analysis of the metabolome of the human seminal plasma, and used chemometrics on the patterns of Raman spectra obtained. Significant changes were observed in the metabolome of the human seminal plasma of asthenozoospermic patients
Dynamic Parameters of Saturated and Unsaturated Sand at Different Range of Shear Strain Levels in Cyclic Simple Shear Test
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
In this investigation, a series of cyclic simple shear tests were carried out in order to evaluate dynamic parameters of Babolsar and Toyoura sand at levels of saturation 25, 50, 75 and 100%. 96 tests were conducted using SGI type cyclic simple shear device. The specimens were cylindrical, with 7cm diameter and 2.2 cm height. The tests were performed under both drained condition (constant-load) at levels of saturation 25, 50%, and undrained condition at levels of saturation 75, 100%. All tests were performed under vertical consolidation stress of 50 and 150 kPa, relative density of 30 and 70% and cyclic shear strain of 0.5, 5 and 10%. The tests were shear strain-controlled with an...
Evaluation of Dynamic Properties of Plastic Concrete Using Bending Disk Tests in Small Strain Range
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
Evaluation of the compression wave velocity (Vp ) and small strains elastic modulii of various types of plastic concrete specimens in unconfined and triaxial compression tests using piezoelectric transducers was performed in this study. Plastic concrete consists of aggregates, cement, water and bentonite, mixed at a high water cement ratio, to produce a ductile material. It is used for creating an impermeable cut-off wall for seepage control in highly permeable dam foundations. A plastic concrete cut-off wall acts essentially as a barrier to stop or reduce the groundwater flow. In this study the effect of specimen age, water-cement ratio, bentonite-cement ratio, confining pressure, wave...
Evaluation of Strength Parameters of Plastic Concrete by Triaxial Tests
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
This research are divided into the two main parts. In the first part, effective parameters for prediction of 28 days strength of plastic concrete have been determined. In this part, data mining operation was done on some informations which was sent from Silveh Dam construction site. In dam construction site, for quality control of plastic concrete which used in building of cut off wall some tests are done regurlarly in 7 and 28 days of concrecte production. In first part we used artificial neural network for predicting of relation between 28 days strength parameter and varios parameters of dam mixture content. The results has shown that the most effective parametes on 28 days strength...
Investigation of Dynamic Response of Shallow Foundations on Layered Soil Medium by Physical Modeling
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
Dynamic impedance functions method is most recent approach in the analysis of soil-foundation dynamic interaction, and presented for massless rigid foundations. Impedance functions are frequency dependent functions, and used to obtain dynamic response of foundation with arbitrary mass subjected to dynamic loading of any frequency and magnitude. The important assumptions for appropriate useof mentioned method are rigidity of foundation and visco-elastic behavior of the soil beneath the foundation. In this study, experimental vertical impedance functions of square and circular foundations have been investigated,using physical modeling tests. A granular soil layer with finite thickness...
Investigation of Dynamic Response of Shallow Foundations on Sandy Soil to Horizontal Harmonic Loading by Physical Model Tests
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
The most important step in current dynamic analysis of machine foundations is determining dynamic impedance functions. Impedance functions are defined as ratios of applied force or moment to induced displacement or rotation angle of foundation. In this research, horizontal dynamic response of foundation on homogeneous halfspace was investigated using physical modeling. Soil medium was built in a 1mx1mx0.8m steel box whose interior walls were covered by 0.1m of sawdust (a material with high damping). In order to prevent possible reflection of waves, this cover was extended to the box bottom with 0.2 m thickness. Sand raining method was used to build soil medium. In this method, with...
Electrochemical Preparation and Study of Transitional Metal Mixed Oxides as Supercapacitor Electrodes
, Ph.D. Dissertation Sharif University of Technology ; Gobal, Fereydoon (Supervisor)
Abstract
In this thesis, the improving effects of deposited metal oxides onto or next to each other and the advantages of every metal oxide were considered. In the next step, the substrate improvement was studied and the porous metal oxides with ideal supercapacitive properties with porosity increase of substrate were obtained.CoFeO2 supercapacitor was prepared by chronoamperometric ethod.CoFeO2waselectrodeposited at room temperature and presents wide potential window and good capacitive properties in comparison with other metal oxides.Layers of cobalt and manganese oxides were co-deposited or deposited on top of each other or next to each other by chronometric method onto stainless steel substrate....
Survey the Change of Phreatic Line Position in the First Filling of Earth Dams until Steady State Seepage
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
Since seepage-related problems account for the cause of more than forty percent of dam failure seepage analysis serves as one of the most significant stage in the design process of an embankment dam. Currently a steady seepage analysis in a typical or maximum cross section of the dam is formed instead of transient seepage analysis for simplicity. In this way, for the change of condition (unsaturated to saturated) in the first filling of dams and it’s effects on behavior and reaction of dams until the steady seepage condition established; the results of steady seepage analysis cannot be satisfactory. In this thesis, based on finite element method and with assumption of saturated-unsaturated...
Comparison of Slopes' Pgds Derived From Newmark Rigid Block Theory With 1g Shaking Table Model Tests
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
Moderate to large magnitude earthquakes trigger hundreds to thousands of slope stability failures and landslides in coherent masses. In many earthquakes, landslides have been responsible for as much or more damage than all other seismic hazards combined. Earthquake-induced landslides have a detrimental impact on the serviceability of slopes by damaging nearby structures, roadways, utilities, power lines and communication networks. In this research large-scale shaking table model tests were conducted to study slope behavior under earthquake conditions on Sharif University shaking table. The model slopes were installed into a model box with a length of 3 m, width of 1 m, and height of 1.5 m. A...
Investigation of Dynamic Response of Shallow Foundations on Layered Soils to Horizontal Harmonic Loading by Physical Model Tests
, M.Sc. Thesis Sharif University of Technology ; Jafarzadeh, Fardin (Supervisor)
Abstract
Increasing requirements of industries and research institutes to analytical results of interaction soil-foundation related systems, reveals the importance of the dynamic impedance functions than ever before. The dynamic impedance function relations are presented for massless rigid foundations which is possible to obtain dynamic response of foundations for different frequencies and masses accordingly. In this study, the dynamic impedance functions were investigated using physical modeling tests on sandy soil with finite thickness soil stratum over bedrock. The tests were carried out inside a steel container of dimensions 110.8m in length, width and height respectively which was filled into...
Determination of Mechanical and Fracture Properties of Nanostructure of Severe Shot Peened A356.0 at Room Temperature
,
M.Sc. Thesis
Sharif University of Technology
;
Farrahi, Gholamhossein
(Supervisor)
Abstract
The most failures caused by wear, fatigue and corrosion are very sensitive to surface of material. Since the most failures starts or occurs at the surface of material, so control and improvement of the surface properties can have a significant effect on increasing the service life and improve the overall behavior of the material. Reforming of the structure and grain size is one of the methods to improve elastic properties, hardness, softness, toughness, etc. Also the macroscopic residual stresses in fracture toughness test specimens, can have tremendous effect on fracture toughness measurements. Many methods are used to modify the surface structure and to create a compressive residual stress...