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Analytical Modelling and Optimization of Disk Type, Slot Less Resolver
, M.Sc. Thesis Sharif University of Technology ; Nasiri Gheidari, Zahra (Supervisor)
Abstract
Resolvers, due to their robust structure, are widely used in automation systems. Among the types of resolvers, the accuracy of the Wound Rotor (WR) resolver in the occurrence of common mechanical errors is higher than other types of resolvers. therefore, in this thesis, an AFWRR is studied to improve the performance. Increasing the number of poles in WR resolvers is a good solution for increasing the accuracy of these electromagnetic position sensors. However, high-speed WR resolvers due to employing fractional slot windings suffer from rich sub-harmonics in the induced voltages. A common solution for suppressing the undesirable sub-harmonics is using multi-layer winding with appropriate...
The Synthesis of Graphene-Nanobubbles and Investigation of their Potential Synergistic Effect on Bacterial Cells
, Ph.D. Dissertation Sharif University of Technology ; Akhavan, Omid (Supervisor) ; Maddah Hosseini, Hamid Reza (Supervisor) ; Bakhsi, Bita (Co-Supervisor)
Abstract
Recently, nanotechnology has promised to create and/ or improve therapeutic methods which in turn remain minimum side effects by employing synergistic effects of nanostructures. However, a comprehensive understanding of the interactions between nanostructures and building blocks of the biological systems (cells) is essential to create innovative therapeutic methods and compound and also predict their behavior for upcoming applications. In this thesis for the first time, synergistic effects of graphene-nanobubbles in interactions with bacterial (as the simplest model) cells were investigated. Therefore, at the first step, production of nanobubbles (NBs) in the presence of two-dimensional...
Design, analysis, and prototyping of a new wound-rotor axial flux brushless resolver
, Article IEEE Transactions on Energy Conversion ; Volume PP, Issue 99 , 2016 ; 08858969 (ISSN) ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
Resolvers are electromagnetic position sensors that are widely used in industrial applications. In this study, a new axial flux brushless resolver (AFBR) with a wound rotor is introduced. In the proposed resolver, the core of the rotary transformer (RT) is omitted, and an innovative design is used to supply the excitation winding of the resolver. The proposed resolver can be built with smaller dimensions, and its thermal stability and mechanical strength are increased compared with conventional AFBRs. The performance of the proposed structure is simulated and optimized by using a 3-D time-stepping finite element method. The effect of the leakage flux of the rotary transformer on the...
Design, performance analysis, and prototyping of linear resolvers
, Article IEEE Transactions on Energy Conversion ; Volume 32, Issue 4 , 2017 , Pages 1376-1385 ; 08858969 (ISSN) ; Sharif University of Technology
2017
Abstract
Linear position sensors are widely used in linear motion-control systems. In this paper, the design, optimization, performance analysis, and prototyping of a linear resolver (LR) are discussed. Mathematical model of the proposed structure is presented based on a simple design-oriented method. Then, a comprehensive iterative design algorithm considering design constraints of linear electromagnetic sensors is proposed. All resistances and inductances of the designed LR are calculated based on the design parameters. Then, a 3-D time-stepping finite-element method is used to validate the design, optimization, and analytical model. Finally, a prototype of the sensor is built and tested....
Design, Analysis, and prototyping of a new wound-rotor axial flux brushless resolver
, Article IEEE Transactions on Energy Conversion ; Volume 32, Issue 1 , 2017 , Pages 276-283 ; 08858969 (ISSN) ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
Resolvers are electromagnetic position sensors that are widely used in industrial applications. In this study, a new axial flux brushless resolver (AFBR) with a wound rotor is introduced. In the proposed resolver, the core of the rotary transformer (RT) is omitted, and an innovative design is used to supply the excitation winding of the resolver. The proposed resolver can be built with smaller dimensions, and its thermal stability and mechanical strength are increased compared with conventional AFBRs. The performance of the proposed structure is simulated and optimized by using a three-dimensional time-stepping finite element method. The effect of the leakage flux of the RT on the excitation...
"The Paakshooy": A Robotics Cell for Washing and Preparation of a Cropse for Burial Compatible with Islamic Laws
, M.Sc. Thesis Sharif University of Technology ; Meghdari, Ali (Supervisor)
Abstract
Washing a dead person’s body and dressing the corpse prior to burial is an act of love and necessity in many religions. Since the deceased loses all bodily functions at time of death, cleaning the body to eliminate odors is generally a hard and unpleasant task for many to perform. It has also been reported that tens of thousands of microbes are present on every square centimeter of a human corpse which is always a health risk to the persons performing the task. Among Islamic nations, preparation of the corpse is usually carried out in washing rooms (Ghassalkhaneh) of cemeteries in large cities. This preparation consists of two important operations namely as washing of the corpse (Ghosl)...
Inventory Ordering System with Fuzzy Parameters in Supply Chain
, M.Sc. Thesis Sharif University of Technology ; Hajji, Rasool (Supervisor)
Abstract
Inventory control has been always considered important due to its prominent role in managing and better application of resources in the field of operational systems. Ordering system or review stock policy in supply chain management can be mentioned as one of the inventory control study fields of management. A lot of researches have been done in investigating ordering system in supply chain under certainty conditions; however, since the real world is full of uncertainties, parameters such as demand cannot be predicted exactly and we encounter with ambiguity. In this case, using crisp (exact) values can cause to decide wrongly (a wrong decision). On the other hand, due to absence of sufficient...
Path-planning and Control of Space Robots
, M.Sc. Thesis Sharif University of Technology ; Namvar, Mehrzad (Supervisor)
Abstract
Control of many mechanical systems such as satellites lies on the control of space robots. Control of space robots has many theoric complexities because of the presence of non-holonomic constraints due to angular momentum conservation. Unlike fixed-base robots, any movement of space robots manipulator has a reaction on the robot base and moves it. Thus manipulator’s movement toward desired configuration rotates the robot base and as a result appropriate attitude may not be attained. Therefore an appropriate path is required to achieve the desired configuration and the base attitude reaches its desired value. In this thesis, first the dynamic of space robots and the interaction between the...
Two Methods of Backtesting for Evaluating Value-at-Risk Models
, M.Sc. Thesis Sharif University of Technology ; Zamani, Shiva (Supervisor)
Abstract
This thesis proposes two methods for backtesting VaR models. The first is the combination of saddlepoint technique with Berkowitz backtesting and the second is based on maximum loss which uses Fischer-Tippet theorem to backtest VaR models. Monte Carlo simulation studies show that the power of these new backtests, especially the latter which is easy to use, is not less than complex Backtests that are well-known for their accuracy
Managing Shared Use of an FPGA-based Accelerator among Virtual Machines
, M.Sc. Thesis Sharif University of Technology ; Goudarzi, Maziar (Supervisor)
Abstract
Using accelerators inside high speed servers can reduce execution time of applications and total power usage of the system. Sharing accelerator between virtual machines of a server decrease both cost and power, however it won’t provide the gained speedup of using dedicated accelerator for each virtual machines. Creation of an appropriate set of accelerators required for virtual machines, management of accesses to the accelerator, prioritizing and scheduling of requests and reconfiguration type of accelerator are the most important challenges that this project has been dealt with. The main objective of this project is implementing the necessary infrastructure to share an FPGA-based...
Structural Health Monitoring of Aerospace Stiffened Panels Using Lamb Wave Propagation
, M.Sc. Thesis Sharif University of Technology ; Abedian, Ali (Supervisor)
Abstract
In recent years world countries faced with the ageing aircraft fleet problem which increased the repair and maintenance costs of these aircrafts. The non-destructive inspection methods are common inspection methods of old aircrafts. To do this, the aircraft must test with a certain time scheduled inspection programme in a hangar. This method not only increased the repair and maintenance costs but also affects the flight schedule. To overcome this problem, the structural health monitoring can use to online monitoring the structure and when it needs for repair, the aircraft send to hanger. So, repair and maintenance costs minimize while the flight schedule less affected. One of the structural...
Fabrication of porous scaffolds with decellularized cartilage matrix for tissue engineering application
, Article Biologicals ; Volume 48 , 2017 , Pages 39-46 ; 10451056 (ISSN) ; Mashayekhan, S ; Sharif University of Technology
Academic Press
2017
Abstract
Due to the avascular nature of articular cartilage, damaged tissue has little capacity for spontaneous healing. Three-dimensional scaffolds have potential for use in tissue engineering approach for cartilage repair. In this study, bovine cartilage tissue was decellularized and chemically crosslinked hybrid chitosan/extracellular matrix (ECM) scaffolds were fabricated with different ECM weight ratios by simple freeze drying method. Various properties of chitosan/ECM scaffolds such as microstructure, mechanical strength, swelling ratio, and biodegradability rate were investigated to confirm improved structural and biological characteristics of chitosan scaffolds in the presence of ECM. The...
Dynamic FPGA-accelerator sharing among concurrently running virtual machines
, Article Proceedings of 2016 IEEE East-West Design and Test Symposium, EWDTS 2016, 14 October 2016 through 17 October 2016 ; 2017 ; 9781509006939 (ISBN) ; Goudarzi, M ; Sharif University of Technology
2017
Abstract
Using an FPGA as a hardware accelerator has been prevalent, to speed up compute intensive workloads. However, employing an accelerator in virtualized environment enhances complexity, because accessing the accelerator from virtual machines has significant overhead and sharing it needs some considerations. We have implemented adequate infrastructure to share an FPGA-based accelerator between multiple virtual machines with negligible access overhead which dynamically implements virtual machines' accelerators. In our architecture each user process from a virtual machine can directly access the FPGA over PCIe link and reconfigure its accelerator in the specified part of FPGA at run-time. The...
Laboratory Investigation of the Effects of Sodium Chloride Concentration on Soil Water Retention Curve and Volumetric behavior Using an Unsaturated Automatic Oedometer
, M.Sc. Thesis Sharif University of Technology ; Sadeghi, Hamed (Supervisor)
Abstract
Laboratory studies to investigate the effects of different saline concentrations (such as sodium chloride or calcium chloride) on the soil water retention behavior of clayey soils and their volumetric changes have received much attention recently. However, many previous studies have investigated these effects in only one path of the SWRC (wetting or drying path) and the effects of saline concentration on hydraulic hysteresis have not been considered. In addition, researchers have frequently studied these effects on SWRC on clay samples, and little research has been done on collapsible soils. Therefore, the most important purpose of this study is to investigate the effects of increasing...
Simulation and visualization environment for nonlinear helicopter flight dynamics
, Article General Aviation Technology Conference and Exhibition, Wichita, KS, 29 August 2006 through 31 August 2006 ; 2006 ; 01487191 (ISSN) ; Rezazade, M ; Sharif University of Technology
SAE International
2006
Abstract
The Analytic 6 D.O.F. dynamic model of a helicopter is developed for 3D computer generated imagery simulator. Analytic expressions for the forces and moments on the various helicopter components are derived. By using the forces and moments equilibrium, helicopter trim point is determined using Newton's method of solving the nonlinear set of trim equations. The equations of motion for the fuselage six degree of freedom are assembled by applying Newton's law of motion relating the applied forces and moments to the resulting translational and rotational acceleration. Visual C++ programming software, utilized as a platform will interact to MATLAB Aircraft Instrument ActiveX and 3DSTATE for...
Improvement of Level Crossing Sampling’s Performance in Sample Reconstruction, Data Compression and Sampler Stages
, M.Sc. Thesis Sharif University of Technology ; Marvasti, Farokh (Supervisor)
Abstract
Level crossing sampling is a sampling method in which a sample is taken whenever signal crosses predefined and specific levels. In this dissertation, some recommendations are made in order to increase the sampler’s performance in the sampling, data compression, and reconstruction stages.The IMATMirror algorithm is introduced in the sample reconstruction stage. This algorithm is derived from the IMAT reconstruction method. However, additional data processing is done in each iteration, causing the reconstructed signal to satisfy some properties of the Level-Crossing samples.In order to solve the problem of level crossing sampling of extremely bursty signals (ECG signals for example), a sampler...
Effect of Laser Shock Peening on Fretting Fatigue Behaviour of 316L Stainless Steel
, M.Sc. Thesis Sharif University of Technology ; Farrahi, Gholamhossein (Supervisor)
Abstract
Fretting fatigue occurs at the point of contact of two parts that are under dynamic loading. During this phenomenon, due to the force applied at the contact point, deformation occurs and causes slip-stick zones, which intensifies the effect of surface degradation and crack nucleation happens earlier. In this research, the improvement of fretting fatigue life under combined loading by induction of compressive residual stresses by laser pinning process in the sample has been investigated. The laser shock peening process is a method by which residual stress is created in the sample and can improve fatigue life. The material used is 316L stainless steel, which has many industrial applications....
Comparison of Active and Passive Control for Suppressing the Vibration of Regenerative Chatter in Nonlinear Milling Process: Application for Machining of Nonlinear Cantilever Plates
, M.Sc. Thesis Sharif University of Technology ; Moradi, Hamed (Supervisor)
Abstract
One of the most important processes in the manufacture of mechanical parts in the industry is the machining process. High-speed milling is growing in aerospace, automotive, and many other industries due to advantages such as high material removal rates and better surface finish. However, the instability caused by self-excited vibration (chatter) is not only one of the main limitations for the productivity and quality of the workpiece but also reduces the life of machines and tools. In this research, after introducing the matter of milling flexible parts, the basic concepts of machining are first described, and common terms in machining are explained. Then, a review of past research has been...
Planning Before, and Emergency Response After, Disaster in Transportarion Networks
, Ph.D. Dissertation Sharif University of Technology ; Nasiri, Habibollah (Supervisor)
Abstract
Natural disasters claim major losses in human lives and belongings, as well as national infrastructures. Taking major earthquake as an example, the study has considered two sides of the problem, both before and after the incident. The former side is formulated as a multipartite optimization problem, in which each party’s activities are directed toward the long-term solution of the original problem. A heuristic method to solve the multipartite problem, and solve three example problems to show the applicability of the method was proposed. The solutions of example problems show that a directed problem solution reaches a better solution (in terms of the objective function value) than the...
Modeling International Air Itinerary Choice
, Ph.D. Dissertation Sharif University of Technology ; Nasiri, Habibollah (Supervisor)
Abstract
Modelling passengers’ itinerary choice behaviour is valuable to understand the increasingly competitive airline market and predicting air travel demand. Research in the choice behaviour of air travellers has evolved to include an analytical focus on variation in the sensitivities of travellers to factors influencing itinerary choice. That is, some choice studies have moved beyond a focus on assumed representative, mean-level sensitivities toward a goal of representing the distribution of preferences across a sample. An important issue that remains is whether the insight gained in previous studies, which focussed on preferences in mature markets with relatively high per-capita rates of air...