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machinability
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Real – time Transient Stability Assessment Using Adaboost Algorithm
, M.Sc. Thesis Sharif University of Technology ; Ranjbar, Ali Mohammad (Supervisor)
Abstract
Because of deregulation and economic issues, power systems operate closer to their stability limits than before. So, security assessment of power system has gained a lot of attention in power system studies. Transient stability and its real time assessment is a great concern in power system security. Among all different methods for transient stability assessment, Automatic Learning methods are used the most in real time assessment problems. These methods can provide fast assessment of transient stability, sensitivity analysis and means of control of the transient stability phenomena. In this paper Adaboost algorithm is used as a brand new method in transient stability assessment of a medium...
VMs Allocation Algorithms Aimed at Minimizing Latency in Cloud Environment
, Ph.D. Dissertation Sharif University of Technology ; Movaghar, Ali (Supervisor)
Abstract
Cloud computing empower the big data management in a faster, cheaper and more effective way. Geo-distributed data-centers in cloud systems are becoming increasingly popular due to their lower end-user perceived latency and increased reliability in distributed applications. Therefore, the number of cloud service users has increased worldwide, and cloud service providers have been deploying and operating data centers to serve cloud users. The efficiency of a resource allocation is an important concern in cloud management. The cloud manager faces applications whose VMs are far apart and need to interact with end-users, access distributed data and communicate with each other. In such...
Control of the Concurrency and Consistency Problem in Readable/Writable Virtual Machine Introspection
, M.Sc. Thesis Sharif University of Technology ; Kharrazi, Mahdi (Supervisor)
Abstract
Over the last years, research about writable virtual machine introspection has been started. This approach has the benefits of readonly virtual machine introspection. Additionally, it has more applications, such as automated defense against malware programs, than the read-only approach. In the read-only VMI, data is gathered from virtual machine hardware states and then analysis in virtual machine monitor. In writable one, hypervisor can modify virtual machine kernel state. Consistency issue is an essential challenge for out-vm writable VMI. In the best of our knowledge, only one implementation try to solve this consistency issue. However it cannot resolve this issue completely. Other VMI...
Genome-Wide Association Study via Machine Learning Techniques
, M.Sc. Thesis Sharif University of Technology ; Fatemizadeh, Emad (Supervisor) ; Motahari, Abolfazl (Co-Advisor)
Abstract
Development of DNA sequencing technologies in the recent years magnifies the need for computational tools in genomic data processing, and thus has attracted inten- sive research interest to this area. Among them, Genome-Wide Association Study (GWAS) refers to discovering of causal relationships among genetic sequences of living organisms and the macroscopic phenotypes present in their physiological structure. Chosen phenotypes for genomic association studies are mostly vulnerability or im- munity to common genetic diseases. Conventional methods in GWAS consists of statistical hypothesis testing algorithms in case/control approaches; Most of which are based upon single-locus analysis and...
Hybrid Multiscale Modeling of Cancer Cell Behavior
, Ph.D. Dissertation Sharif University of Technology ; Habibi, Jafar (Supervisor)
Abstract
Cancer is a class of diseases characterized by out-of-control cell growth. Cancer is among the leading causes of death worldwide.Cancer modeling is increasingly being recognized as a powerful tool to refine hypotheses, focus experiments, and enable predictions that are more accurate.We investigate a three-dimensional multiscale model of vascular tumour growth, which couples blood flow, angiogenesis, vascular remodelling, nutrient/growth factor transport, movement of, and interactions between, normal and tumour cells. We constructed a hybrid multi- scale agent-based model that combines continuous and discrete methods.Each cell is represented as an agent. The agents have rules that they must...
Improving Graph Construction for Semi-supervised Learning in Computer Vision Applications
, M.Sc. Thesis Sharif University of Technology ; Rabiee, Hamid Reza (Supervisor)
Abstract
Semi-supervised Learning (SSL) is an extremely useful approach in many applications where unlabeled data can be easily obtained. Graph based methods are among the most studied branches in SSL. Since neighborhood graph is a key component in these methods, we focus on methods of graph construction in this project. Graph construction methods based on Euclidean distance have the common problem of creating shortcut edges. Shortcut edges refer to the edges which connect two nearby points that are far apart on the manifold. Specifically, we show both in theory and practice that using geodesic distance for selecting and weighting edges results in more appropriate neighborhood graphs. We propose an...
Numerical Simulation of Laser Assisted Machining of Hard-to-Machine Alloys
,
M.Sc. Thesis
Sharif University of Technology
;
Movahhedy, Mohammad Reza
(Supervisor)
;
Akbari, Javad
(Supervisor)
Abstract
Laser Assisted Machining is a novel type of machining in which laser beam warms up the workpiece locally. Using laser beam in machining leads to a reduction in machining forces, an increase in tool life and an improvement in surface quality. This study introduces the process, reviews literatures related to it and then, simulates the process thermo-mechanically. A process in which a Gaussian pulsed ND-YAG laser beam of 700w power is used for machining of AISI 52100 is simulated, considering sufficient properties of material. Simulations are done using Abaqus®/Standard and Abaqus®/Explicit softwares. Also, Abaqus®/CAE visual interface, Intel® Visual Fortran compiler alongside with Microsoft...
Automatic Evaluation of Machine Translation Using Abstract Meaning Representation
, M.Sc. Thesis Sharif University of Technology ; Rezae, Saeed (Supervisor) ; Bahrani, Mohammad (Supervisor)
Abstract
Machine Translation Quality Evaluation, compared to the other issues dealt with in the field of Natural Language Processing, is faced with the challenge that the repetition of the translation process from the same linguistic form in the source language will not necessarily lead to a unique linguistic form in the target language. Therefore, considering the fact that the Abstract Meaning Representation (AMR) graph is the same for all the sentences of similar meaning, this thesis has been an attempt to extend the efficiency of AMR graphs to the area of Machine Translation Quality Evaluation. The main research question dealt with in the present thesis was whether the similarity of the AMR graphs...
Machine Learning in 2D Compressed Sensing Datasets
, M.Sc. Thesis Sharif University of Technology ; Babaiezadeh, Massoud (Supervisor)
Abstract
Compressed Sensing (CS) technique refers to the digitalization process that efficiently reduces the number of measurements below the Nyquist rate while preserving signal structure. This technique was originally developed for the analysis of vector datasets. An x ∈R^n vector is transformed into an y ∈R^m vector so that n≪m. For a sufficient number of measurements, this transformation has been shown to preserve the signal structure. Therefore, the technique has been applied to machine learning applications.2D-CS was further developed for matrices (image datasets) so that they could be directly applied to matrices without flattening. X ∈R^(n×n) is transformed into Y ∈R^(m×m) via 2D-CD such...
Steady-state analysis and performance of a brushless doubly fed machine accounting for core loss
, Article IET Electric Power Applications ; Volume 7, Issue 3 , 2013 , Pages 170-178 ; 17518660 (ISSN) ; Tahami, F ; Tavner, P ; Tohidi, S ; Sharif University of Technology
2013
Abstract
In this study a steady-state equivalent circuit for a brushless doubly fed machine (BDFM), based upon earlier work, is introduced which takes account of core losses. Based upon some loss approximations, simple relationships have been derived, which show that the synchronous mode operation, in terms of core loss, of the BDFM is similar to the cascaded doubly fed machine. The slip-dependence of core loss resistances in the equivalent circuit has been investigated by applying energy conservation to derive machine steady-state torque-speed relations in the presence of core loss. Experimental speed measurements of the BDFM in the simple induction mode were used to identify the core loss...
Stochastic scheduling with minimizing the number of tardy jobs using chance constrained programming
, Article Mathematical and Computer Modelling ; Volume 57, Issue 5-6 , 2013 , Pages 1154-1164 ; 08957177 (ISSN) ; Salmasi, N ; Sharif University of Technology
2013
Abstract
In this research, two scheduling problems i.e., single machine scheduling problem with minimizing the number of tardy jobs (1∥∑Uj) and two machine flow shop scheduling problem with a common due date and minimizing the number of tardy jobs (F2{pipe}dj=d{pipe}∑Uj) are investigated in a stochastic setting in the class of non-preemptive static list policies. It is assumed that the processing times of jobs are independent random variables. The stochastic problems are solved based on chance constrained programming. An equivalent deterministic problem is generated for each stochastic problem by linearization of the chance constraints. Then, the generated deterministic problems are solved using...
Dynamic model for Brushless Doubly-Fed Machine with stator winding faults
, Article PEDSTC 2010 - 1st Power Electronics and Drive Systems and Technologies Conference, 17 February 2010 through 18 February 2010 ; February , 2010 , Pages 316-322 ; 9781424459728 (ISBN) ; Sotoodeh, P ; Oraee, H ; Sharif University of Technology
2010
Abstract
In this paper, a detailed analytical model for dynamic analysis of the Brushless Doubly-Fed Machine is presented. The model is capable to predict the machine behavior under different modes of operation including: simple induction mode, cascade mode and synchronous mode, both with and without winding faults and unbalanced excitations. The proposed approach employs the basic principles of the generalized harmonic theory for calculating self inductances and mutual inductances of circuits with any distribution of conductors. Dynamic equations of modified coupled-circuit method are then solved to compute the currents flowing in the stator windings and rotor loops
BSS: Boosted steganography scheme with cover image preprocessing
, Article Expert Systems with Applications ; Volume 37, Issue 12 , December , 2010 , Pages 7703-7710 ; 09574174 (ISSN) ; Jamzad, M ; Sharif University of Technology
2010
Abstract
The existing powerful steganalyzers can find out the presence of secret information in images with high accuracy. Increasing the embedding capacity of cover images reduces the detection risk of stego images. In this respect, we introduce boosted steganography scheme (BSS) that has a preprocessing stage before applying steganography methods. The goal of BSS is increasing the undetectability of stego images. Due to the dependence of embedding capacity of images to their content, we proposed an ensemble steganalyzer to estimate the embedding capacity of each cover image. Since the content of cover images has less significance in steganography, therefore to have more security, the steganographer...
The brushless doubly-fed machine vector model in the rotor flux oriented reference frame
, Article 34th Annual Conference of the IEEE Industrial Electronics Society, IECON 2008, Orlando, FL, 10 November 2008 through 13 November 2008 ; January , 2008 , Pages 1415-1420 ; 9781424417667 (ISBN) ; Oraee, H ; Abdi, E ; Shao, S ; Mc Mahon, R ; Sharif University of Technology
IEEE Computer Society
2008
Abstract
The paper presents the vector model of the Brushless Doubly-Fed Machine (BDFM) in the rotor flux oriented reference frame. The rotor flux oriented reference frame is well known in the standard AC machines analysis and control. Similar benefits can be sought by employing this method for the BDFM The vector model is implemented in MATLAB/SIVIULINK to simulate the BDFM dynamic performance under different operating conditions. The predictions from the vector model are compared to those from the coupled circuit model in simulation. The results are shown for the cascade mode of operation. © 2008 IEEE
Another approach to detection of abnormalities in MR-images using support vector machines
, Article ISPA 2007 - 5th International Symposium on Image and Signal Processing and Analysis, Istanbul, 27 September 2007 through 29 September 2007 ; 2007 , Pages 98-101 ; 9789531841160 (ISBN) ; Dehestani Ardekani, R ; Torabi, M ; Fatemizadeh, E ; Sharif University of Technology
2007
Abstract
In this paper we will address two major problems in mammogram analysis for breast cancer in MR-images. The first is classification between normal and abnormal cases and then, discrimination between benign and malignant in cancerous cases. Our proposed method extracts textural and statistical descriptive features that are fed to a learning engine based on the use of Support Vector Machine learning framework to categorize them. The obtained results show excellent accuracy in both classification problems, that proves the appropriate combination of our features and selecting powerful classifier i.e. Support Vector Machine leads us to a brilliant outcome
An investigation on the compressibility of aluminum/nano-alumina composite powder prepared by blending and mechanical milling
, Article Materials Science and Engineering A ; Volume 454-455 , 2007 , Pages 89-98 ; 09215093 (ISSN) ; Hafizpour, H. R ; Simchi, A ; Sharif University of Technology
2007
Abstract
The densification response of aluminum powder reinforced with 5 vol.% nanometric alumina particles (35 nm) during uniaxial compaction in a rigid die was studied. The composite powder was prepared by blending and mechanical milling procedures. To determine the effect of the reinforcement nanoparticles on the compressibility of aluminum powder, monolithic Al powder, i.e. without the addition of alumina, was also examined. It was shown that at the early stage of compaction when the rearrangement of particles is the dominant mechanism of the densification, disintegration of the nanoparticle clusters and agglomerates under the applied load contributes in the densification of the composite powder...
A new upper bound solution for analysis of the radial forging process
, Article International Journal of Mechanical Sciences ; Volume 48, Issue 11 , 2006 , Pages 1264-1272 ; 00207403 (ISSN) ; Karimi Taheri, A ; Movahhedy, M. R ; Sharif University of Technology
2006
Abstract
Radial forging is an open die forging process used for reducing diameter of shafts, tubes, stepped shafts and axels, and creating the internal profiles for tubes such as rifling the gun barrels. In the present research, a new model based on calculating the deformation work was developed to find an upper bound limit for the deformation load in the case of radial forging of rods and tubes. Also, the model was used to assess the effects of the process parameters. The accuracy of the model was tested by comparing the predicted results with those achieved from the experiment at work of Uhlig [Investigation of the motions and the forces in radial swaging. Doctoral Dissertation, Technical...
A compiler for multi-key homomorphic signatures for Turing machines
, Article Theoretical Computer Science ; Volume 889 , 2021 , Pages 145-170 ; 03043975 (ISSN) ; Fiore, D ; Venturi, D ; Amini, M ; Sharif University of Technology
Elsevier B.V
2021
Abstract
At SCN 2018, Fiore and Pagnin proposed a generic compiler (called “Matrioska”) allowing to transform sufficiently expressive single-key homomorphic signatures (SKHSs) into multi-key homomorphic signatures (MKHSs) under falsifiable assumptions in the standard model. Matrioska is designed for homomorphic signatures that support programs represented as circuits. The MKHS schemes obtained through Matrioska support the evaluation and verification of arbitrary circuits over data signed from multiple users, but they require the underlying SKHS scheme to work with circuits whose size is exponential in the number of users, and thus can only support a constant number of users. In this work, we propose...
Using a combination of vibration absorber and a classical active controller to suppress the chatter vibration and increase the stability in turning process
, Article 10th International Conference on Modern Circuits and Systems Technologies, MOCAST 2021, 5 July 2021 through 7 July 2021 ; 2021 ; 9781665418478 (ISBN) ; Moradi, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
Free, forced, and self-excited vibrations are the three main types of machine tool vibrations. Self-excited vibration is the most important type of destructive vibration in machining. The most important factor in increasing the chipping rate, stability, and tool life is decreasing this type of destructive vibration. In this paper, we aim to introduce a method to control the self-excited vibrations by the means of the combining a vibration absorber as a passive controlling method and a classical active controller such as PID or compensator or the other classical methods. Utilizing the SIMULINK toolbox of MATLAB software, first, we designed and added the vibration absorber to the model...
Compressed coded distributed computing
, Article IEEE Transactions on Communications ; Volume 69, Issue 5 , 2021 , Pages 2773-2783 ; 00906778 (ISSN) ; Li, S ; Maddah Ali, M. A ; Avestimehr, A. S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
Communication overhead is one of the major performance bottlenecks in large-scale distributed computing systems, in particular for machine learning applications. Conventionally, compression techniques are used to reduce the load of communication by combining intermediate results of the same computation task as much as possible. Recently, via the development of coded distributed computing (CDC), it has been shown that it is possible to enable coding opportunities across intermediate results of different computation tasks to further reduce the communication load. We propose a new scheme, named compressed coded distributed computing (in short, compressed CDC), which jointly exploits the above...