Finite element analysis of mechanical performance of nitinol biliary stent: effect of material properties [electronic resource]

, Article Materials Research Innovations ; Vol 17, No. 2, 2013, 53-59 Nematzadeh, F. (Fardin) ; Sadrnezhaad, K ; Sharif University of Technology

Abstract

Stent implantation has been regarded as a major strategy to solve gastrointestinal diseases such as biliary obstruction during the last decade. The application of nitinol superelastic stents has been recently considered for minimising such problems as restenosis after stent implantation, the ability to low stent twist, unsuitable dynamic behaviour and inadequate strength radial of stent. In the present article, the effects of material properties on mechanical performance of Z shaped nitinol wire stent under crushing test for clinical applications are studied by finite element modelling. Nitinol stent shows better mechanical and clinical performance after applying 90% crushing, less chronic...

Effects of design parameters and A f temperature on superelastic behaviour of Nitinol stent for application in biliary duct: finite element analysis [electronic resource]

, Article Materials Technology: Advanced Performance Materials ; Vol. 29, No. 2, 2014, 65-75 Nematzadeh, F. (Fardin) ; Sadrnezhaad, K ; Sharif University of Technology

Abstract

For more than a decade, stent implantation has been strategically used for solving gastrointestinal dilemmas such as biliary stenosis. Predicaments like insufficient radial strength, low twisting ability, inappropriate dynamic behaviour and restenosis are expected to be solved by the introduction of new designs. Superelastic Nitinol stent is an interesting alternative for minimising these tight spots. The application of finite element method to predict metallurgical and geometric behaviour of superelastic Nitinol stents for biliary duct dilatation is supported by conventional crimp tests. Model calculations show that all stents encounter the highest stress in their intersegment curvature....

Effects of Crimping on Mechanical Performance of Nitinol Stent Designed for Femoral Artery: Finite Element Analysis [electronic resource]

, Article Journal of Materials Engineering and Performance ; November 2013, Volume 22, Issue 11, pp 3228-3236 Nematzadeh, F. (Fardin) ; Sadrnezhaad, K ; Sharif University of Technology

Abstract

Nitinol stents are used to minimize improper dynamic behavior, low twistability, and inadequate radial mechanical strength of femoral artery stents. In this study, finite element method is used to investigate the effect of crimping and Austenite finish temperature (A f) of Nitinol on mechanical performance of Z-shaped open-cell femoral stent under crimping conditions. Results show that low A f Nitinol has better mechanical and clinical performance due to small chronic outward force, large radial resistive force, and appropriate superelastic behavior

Utilization of CT Scan Technique to Manipulate the Heterogeneity Effect
in Reservoir Rock Properties Determination

, M.Sc. Thesis Sharif University of Technology Salehi, Maryam (Author) ; Ayatollahi, Shahabodin (Supervisor) ; Fazel Abdol Abadi, Babak (Supervisor) ; Nematzadeh, Mostafa (Co-Advisor)

Abstract

Petrophysical properties of reservoir rocks are of the most important parameters in fluid flow simulation and reservoir characterization. Although in core laboratories some well-known procedures for determination of these parameters are applied, in almost all of them the rocks are assumed to be homogeneous and their properties are taken up as identical in all directions. To eliminate these unrealistic assumptions, an accurate, non-destructive technique with appropriate degree of resolution is required for recognition of internal heterogeneity of cores. Medical “CT Scanner” is one of these techniques whose information in conjunction of conventional experiments could reduce their limitations...

Erratum: Effects of crimping on mechanical performance of nitinol stent designed for femoral artery: Finite element analysis

, Article Journal of Materials Engineering and Performance ; Vol. 23, issue. 4 , 2014 , pp. 1511- ; ISSN: 1059-9495 Nematzadeh, F ; Sadrnezhaad, S. K ; Sharif University of Technology

2014

Abstract

[No abstract available]

Finite element analysis of mechanical performance of nitinol biliary stent: effect of material properties

, Article Materials Research Innovations ; Volume 17, Issue SUPPL 2 , December , 2013 , Pages S53-S59 ; 14328917 (ISSN) Nematzadeh, F ; Sadrnezhaad, S. K ; Sharif University of Technology

2013

Abstract

Stent implantation has been regarded as a major strategy to solve gastrointestinal diseases such as biliary obstruction during the last decade. The application of nitinol superelastic stents has been recently considered for minimising such problems as restenosis after stent implantation, the ability to low stent twist, unsuitable dynamic behaviour and inadequate strength radial of stent. In the present article, the effects of material properties on mechanical performance of Z shaped nitinol wire stent under crushing test for clinical applications are studied by finite element modelling. Nitinol stent shows better mechanical and clinical performance after applying 90% crushing, less chronic...

Effects of crimping on mechanical performance of nitinol stent designed for femoral artery: Finite element analysis

, Article Journal of Materials Engineering and Performance ; Volume 22, Issue 11 , 2013 , Pages 3228-3236 ; 10599495 (ISSN) Nematzadeh, F ; Sadrnezhaad, S. K ; Sharif University of Technology

2013

Abstract

Nitinol stents are used to minimize improper dynamic behavior, low twistability, and inadequate radial mechanical strength of femoral artery stents. In this study, finite element method is used to investigate the effect of crimping and Austenite finish temperature (A f) of Nitinol on mechanical performance of Z-shaped open-cell femoral stent under crimping conditions. Results show that low A f Nitinol has better mechanical and clinical performance due to small chronic outward force, large radial resistive force, and appropriate superelastic behavior

Effects of material properties on mechanical performance of Nitinol stent designed for femoral artery: Finite element analysis

, Article Scientia Iranica ; Volume 19, Issue 6 , December , 2012 , Pages 1564-1571 ; 10263098 (ISSN) Nematzadeh, F ; Sadrnezhaad, S. K ; Sharif University of Technology

2012

Abstract

The Finite element method was used for evaluation of the effects of material properties on the mechanical performance of the new geometry designed for the Z-shaped open-cell femoral artery self-expanding stent, made of Nitinol wire, by application of crushing force. The behavior of the stents, having two sets of properties, was compared. The stents with higher Af temperature show better clinical behavior due to lower chronic outward force, higher radial resistive strength and more suitable superelastic behavior. Model calculations show that a large change of Af temperature could exert a substantial effect on the practical performance of the stent

Effects of the ageing treatment on the superelastic behavior of a nitinol stent for an application in the esophageal duct: A finite-element analysis

, Article Materiali in Tehnologije ; Volume 47, Issue 4 , 2013 , Pages 453-459 ; 15802949 (ISSN) Nematzadeh, F ; Sadrnezhaad, S. K ; Sharif University of Technology

2013

Abstract

The effects of design parameters and material properties obtained with the ageing treatment on the mechanical performance of a z-shaped esophageal-duct nitinol wire stent under the crushing tests for clinical applications are investigated with a finite-element simulation. With 90 % crushing, low chronic outward force, high radial resistive strength and favorable superelastic behavior are attained at the segment angle of 65° and the Af temperature of 24 °C. The performance of the stent is seen to drastically vary with a change of only 1° in the segment angle

Modeling and Analysis of the Effect of Weak link Coupling Between the Mesas Structures of Intrinsic Layered Superconductors

, M.Sc. Thesis Sharif University of Technology Nematzadeh, Mohsen (Author) ; Fardmanesh, Mehdi (Supervisor)

Abstract

During the last decade there have been many attempts to push THz science and technology achievement to the appropriate solid state source for this purpose is a main challenge in this area. One of the best devices which can be used as a source in this gap is the stack of intrinsic Josephson junctions. Josephson junction include a dielectric which is sandwiched between two superconductors and convert the voltage to the electromagnetic wave. After studies in this field for obtaining a suitable source using stack of intrinsic Josephson junctions, an idea which is raised in this area is having a mixer in terahertz gap. The main purpose of this thesis is checking the idea of a structure which can...

Computer Familiarity and Test Validity: Investigating the Relationship among Gender, Age, Mother Tongue, Field of Study and TOEFL iBT ® Results

, M.Sc. Thesis Sharif University of Technology Nematzadeh, Arash (Author) ; Salehi, Javad (Supervisor)

Abstract

Technology introduces different possibilities to different contexts. Educational milieu is one of those situations where technology plays a crucial role. Computer as an outstanding technological feature has changed our daily life. Computer in the educational contexts has affected the way we learn. Every new innovation has its specifications and problems. Computer like other innovations has aspects that should be investigated. In some cases, computer can distort the tests results and be a source of threat for test validity (construct irrelevant variance). Therefore, the researcher chose to analyze the role of this phenomenon in the assessing procedure. Gender, age, mother tongue, and field of...

Attitude towards azeri language in Iran: a large-scale survey research

, Article Journal of Multilingual and Multicultural Development ; Volume 38, Issue 10 , 2017 , Pages 931-941 ; 01434632 (ISSN) Rezaei, S ; Latifi, A ; Nematzadeh, A ; Sharif University of Technology

2017

Abstract

This survey research investigated the attitude of Iranian Azeri native speakers towards Azeri language. A questionnaire was developed and its reliability was estimated (r = 0.74) through a piloting phase on 54 Azeri native speakers. The participants, for the main phase of this study, were 400 Azeri native speakers with different social and educational backgrounds and from some densely Azeri-populated provinces in Iran. They completed either the online or the printed version of the survey, the results of which indicated that Iranian Azeri native speakers have a high level of positive attitude towards their mother tongue in spite of the negligence of this language in the Iranian educational...

Persuasion in political discourse: barak obama’s presidential speeches against ISIS

, Article Vestnik Rossiiskogo Universiteta Druzhby Narodov, Seriya Lingvistika ; Volume 22, Issue 2 , 2018 , Pages 278-291 ; 23129182 (ISSN) Alemi, M ; Latifi, A ; Nematzadeh, A ; Sharif University of Technology

Peoples' Friendship University of Russia 2018

Abstract

The current study was concerned with the use of persuasion by President Obama, the former US president, as a discursive strategy in his two speeches delivered on 7/Aug/2014 and 10/Sep/2014 regarding ISIS. Analysis of these speeches was done by the application of Searle’s typology theory (1978), and pronoun analysis. That is, assertive, directive, commissive, expressive, and declarative speech acts, first person singular and plural pronouns (inclusiveness and exclusiveness), and agency. The findings of the study revealed that assertives were the most frequent speech act utilized in both speeches. Considering the function of assertives, this study showed that President Obama’s major intention...

Effect of material properties on the mechanical performance of nitinol esophageal stent: finite element analysis [electronic resource]

, Article Materials Science Forum ; Volumes 773 - 774, 2014, 9-17 Nematzadeh, F. (Fardin) ; Sadrnezhaad, K ; Kokabi, H. A ; Razani, M ; Mohagheghi, A. H ; Sharif University of Technology

Abstract

Stent placement has been a main approach to treat gastrointestinal diseases during past decade. Nitinol superelastic stents have been considered as a solution to such difficulties as restenosis after implantation, low twisting ability, inadequate radial mechanical strength and inappropriate dynamic behaviors associated with the ducts. In this paper, effects of Af temperatures on mechanical performance of z-shaped Nitinol wire stent under crimping test for clinical applications are investigated by finite element simulation. Having 60% crimping and high radial resistive strength, favorable superelastic behaviors are attained at Af temperature of 22°C. The performance of the stent is seen to be...

Structural changes of radial forging die surface during service under thermo-mechanical fatigue

, Article Materials Science and Engineering A ; Volume 527, Issue 1-2 , 2009 , Pages 98-102 ; 09215093 (ISSN) Nematzadeh, F ; Akbarpour, M. R ; Kokabi, A. H ; Sadrnezhaad, S. k ; Sharif University of Technology

2009

Abstract

Radial forging is one of the modern open die forging techniques and has a wide application in producing machine parts. During operation at high temperatures, severe temperature change associated with mechanical loads and the resultant wearing of the die surface lead to intense variation in strain on the die surface. Therefore, under this operating condition, thermo-mechanical fatigue (TMF) occurs on the surface of the radial forging die. TMF decreases the life of the die severely. In the present research, different layers were deposited on a 1.2714 steel die by SMAW and GTAW, with a weld wire of UDIMET 520. The microstructure of the radial forging die surface was investigated during welding...

Periodic solutions for a semi-ratio-dependent predator-prey dynamical system with a class of functional responses on time scales

, Article Discrete and Continuous Dynamical Systems - Series B ; Volume 9, Issue 2 , 2008 , Pages 267-279 ; 15313492 (ISSN) Mostafa, F ; Hesaaraki, M ; Sharif University of Technology

2008

Abstract

In this paper we explore the existence of periodic solutions of a nonautonomous semi-ratio-dependent predator-prey dynamical system with functional responses on time scales. To illustrate the utility of this work, we should mention that, in our results this system with a large class of monotone functional responses, always has at least one periodic solution. For instance, this system with some celebrated functional responses such as Holling type-II (or Michaelis-Menten), Holling type-III, Ivlev, mx (Holling type I), sigmoidal [e.g., Real and mx2/((A + x)(B +x))] and some other monotone functions, has always at least one ω-periodic solution. Besides, for some well-known functional responses...

Modified Load Scheduling Using Smart Meters

, M.Sc. Thesis Sharif University of Technology Bahrami, Shahab (Author) ; Parniani, Mostafa (Supervisor)

Abstract

Implementation of various incentive-based demand response strategies has great potential to decrease peak load growth and customer electricity bill cost. Using advanced metering and automatic demand management makes it possible to optimize energy consumption, to reduce grid loss, and to release generation capacities for the sake of providing sustainable electricity supply, and reducing electricity bills for the customers. With these objectives, this thesis examines the previously suggested load scheduling programs in both residential and industrial sectors, and proposes new practical strategies for load management. This thesis has mainly focuses on three subdivisions of load management...

The Analysis of Total Productive Maintenance Based on Computerized Maintenance Management System

, M.Sc. Thesis Sharif University of Technology Behshad, Amir (Author) ; mostafavi, mostafa (Supervisor)

Abstract

The main purpose of this thesis is to analyze the total productive maintenance based on computerized maintenance management system. At first, a detailed study on total productive maintenance is performed and then the requirements of this maintenance strategy are specified. Also, a computerized maintenance management system is defined which can help total productive maintenance to reach to its requirements. Finally, a conceptual model and entity-relationship model for computerized maintenance management system data base has been created

Study of HVDC Transmission for Offshore Wind Farms Based on Voltage Source Converters

, M.Sc. Thesis Sharif University of Technology Safaeian, Reza (Author) ; Parniani, Mostafa (Supervisor)

Abstract

In this thesis, DC transmission of offshore wind farms is studied thoroughly. Various system configurations that are introduced in the literatures are discussed and their control scheme for normal conditions and grid faults are studied. Then, the HVDC transmission based on voltage source converter, located between a local offshore ac grid and the onshore ac system is investigated as the most practical choice. The HVDC linke circuit elements are calculated and the control strategies of the offshore and onshore converters are introduced. DFIGs are considered to be the best choice for the offshore wind turbine generators. Then, the system is simulated and the frequency of the offshore grid is...

Feasibility Study of Producing Active Pharmaceutical Ingredient from Conceptual Process to Mass Production-Case Study

, M.Sc. Thesis Sharif University of Technology Tavakoli, Meysam (Author) ; Mostafavi, Mostafa (Supervisor)

Abstract

The main aim of this thesis is to develop the technical knowledge of designing and making active ingredients of domestically produced drugs, decreasing the costs, independency in producing these products, and checking outflow of currency. It also aims to reduce the financial challenges of patients who have to pay huge amounts for such drugs. Conducting research in the field of reverse engineering and using its definition, and attempt in made to get knowledge into the stages of product development process, to determine the technical standards associated with each stage, to recognize how knowledge is shared during this process, and to present some methods of establishing the infrastructure...