Estimating Probability Distribution of Remaining Useful Life of Rolling Element Bearing, Using Data-driven Methods

, M.Sc. Thesis Sharif University of Technology Mollaali, Amirhossein (Author) ; Behzad, Mehdi (Supervisor)

Abstract

Predicting the probability distribution of asset remaining useful life is an essential procedure in the intelligent maintenance. It also plays an important role in improving system reliability and optimizing further decisions. The main concern of this project is to estimate the probability distribution of rolling element bearing remaining useful life. For this purpose, the bearing degradation process is modeled through the statistical models, considering the major variabilities in the degradation process. The models parameters are updated, once a new measurement of the equipment is available. Then, the constructed model is utilized in order to predict the probabitity distribution of...

A new methodology to deal with the multi-phase degradation in rolling element bearing prognostics

, Article Smart Innovation, Systems and Technologies, 3 September 2019 through 5 September 2019 ; Volume 166 , 2020 , Pages 855-869 Mollaali, A ; Behzad, M ; Mirfarah, M ; Sharif University of Technology

Springer Science and Business Media Deutschland GmbH 2020

Abstract

Predicting the residual-life (RL) of rolling element bearings (REBs) is an essential procedure of rotating machinery condition monitoring, in industries. Since the bearing fault propagation has a complicated stochastic nature, the multi-phase phenomenon is probable to happen in the degradation process. By occurrence of the multi-phase phenomenon, the degradation process experiences different phases, with distinct failure rate in each phase. Therefore, the mentioned phenomenon leads to large error in the prediction results of single-phase degradation models. The main concern of the present paper is to consider the effect of multi-phase phenomenon on the prediction confidence level of REBs. In...

Location-aware Key Management in Wireless Sensor Networks

, M.Sc. Thesis Sharif University of Technology Nikounia, Hossein (Author) ; Jahangir, AmirHossein (Supervisor)

Abstract

Wireless sensor networks have many applications, vary in size, and are deployed in a wide variety of areas. They are often deployed in potentially adverse or even hostile environment so security issues are of much concern in these networks. Key management is a fundamental security issue in sensor networks. In this thesis, we are mainly focusing on key establishment and group rekeying schemes aspects of key management. Due to limited resources of sensor networks, key pre-distribution schemes are currently viewed as the most promising solution. Key predistribution in sensor networks refers to the problem of distributing secret keys among sensor nodes prior to deployment. Recently, many key...

A new Temporal Locality Method for Multi-Core Processor data Cache

, M.Sc. Thesis Sharif University of Technology Banihashemi, Borzoo (Author) ; Jahangir, AmirHossein (Supervisor)

Abstract

By increasing speed gap between microprocessors and off-chip Last Level Cache, Optimization in Last Level Cache makes improvement in system performance. With development of new generation of multi-core processors and sharing LLC between these cores, the so called issue of Memory Wall has caused an incremental effect of LLC on system performance. There are three approaches to use this memory more efficiently:
1. Increasing cache capacity
2. Making cache hierarchical and adding different layers to hierarchy
3. Improvement of replacement algorithms in cache memory
The first approach has not been used in regard with limitation of technology and growth of access time due to...

Strain rate sensitivity, work hardening, and fracture behavior of an Al-Mg TiO2 nanocomposite prepared by friction stir processing [electronic resource]

, Article Journal of Metallurgical and Materials Transactions A ; August 2014, Volume 45, Issue 9, P.4073-4088 Khodabakhshi, F ; Simchi, A. (Abdolreza) ; Kokabi, Amirhossein ; Nosko, Martin ; Svec, Peter ; Sharif University of Technology

Abstract

Annealed and wrought AA5052 aluminum alloy was subjected to friction stir processing (FSP) without and with 3 vol pct TiO2 nanoparticles. Microstructural studies by electron backscattered diffraction and transmission electron microscopy showed the formation of an ultra-fine-grained structure with fine distribution of TiO2 nanoparticles in the metal matrix. Nanometric Al3Ti and MgO particles were also observed, revealing in-situ solid-state reactions between Al and Mg with TiO2. Tensile testing at different strain rates determined that FSP decreased the strain rate sensitivity and work hardening of annealed Al-Mg alloy without and with TiO2 nanoparticles, while opposite results were obtained...

, M.Sc. Thesis Sharif University of Technology Khodabakhshi, Farzad (Author) ; Kazeminezhad, Mohsen (Supervisor) ; Kokabi, Amirhossein (Supervisor)

Abstract

Considering that automobile weigth reduction in industry is important, improvement the strength of low carbon steel sheets is important. These sheets can be supported the service condition in lower thicknesses. Bulk nano-structured materials have been mostly attracted in materials science due to their unique physical and mechanical properties. Severe plastic deformation (SPD) is one of the most efficient methods to produce ultra fine grained or nano-structured materials. Materials produced by SPD are of great importance because of (1) non-porous structure, (2) great mechanical properties such as high strength and toughness and (3) proper dimension for mechanical and physical testing. ...

Development of High Entropy Filler Alloy for Brazing of Precipitation Hardened Ni-Base Superalloy IN-738

, M.Sc. Thesis Sharif University of Technology Amirhossein Sajjadi (Author) ; Pouranvari, Majid (Supervisor) ; Tavakoli, Rouhollah (Supervisor)

Abstract

Brazing is a crucial process for repairing and manufacturing high-temperature components made of precipitation-hardened superalloys. Boron-containing filler metals are amongst the most common filler metals used for repairing and joining superalloys. Although boron is an effective MPD in such filler metals, the formation of brittle boride intermetallics in the joining area (Athermal solidification zone and diffusion affected zone), due to the low solubility of boron in the matrix of superalloys, is inevitable. Isothermal Solidification is known as an effective technique for removing boride compounds in the joining area of brazed components. but as the time of isothermal solidification...

The relationship between energy consumption and income inresidential and commercialsectors of Iran using STR

, Article World Applied Sciences Journal ; Volume 22, Issue 6 , Oct , 2013 , Pages 824-830 ; 18184952 (ISSN) Mollaali Kani, A. H ; Abbaspour, M ; Amiri, H ; Beshkhoor, M ; Talaie Shokri, S ; Sharif University of Technology

2013

Abstract

Residential and commercial sectors, share a significant portion of energy consumption in Iran; 37 percent of the total per capita consumption. Therefore, identification of the relation between revenue and energy consumption could be a great assistance to policy makers for clarification of policies employed in energy sector. This paper attempts to explore and analyze the relationship between revenue and energy consumption in residential and commercial sectors for the years 1969 to 2009 in Iran by Smooth Transition Regression Models. Smooth transition regression model is a nonlinear time series model which can be considered as a developed form of Switching Regression Model. The obtained...