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golmohammad--sadjad
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Robust Orientation Estimation Using Imu and Online Machine Learning Based Calibration in the Presence of Distortions
, M.Sc. Thesis Sharif University of Technology ; Khodaygan, Saeed (Supervisor)
Abstract
In this project an optimized and robust orientation estimation method using IMU and magnetic sensors is presented. Magnetic distortion effects in orientation estimation is also one of the main purposes. Proposed sensor fusion algorithm is based on a complementary filter which provides a quaternion estimation as the algebraic solution of a system from inertial/magnetic observations. To develop the basic sensor fusion algorithm some procedures including a simple calculation to deal better with non-gravitational accelerations, decrease the effect of magnetometer in the presence of distortions and online gyroscope bias estimation is added. Also, a method for classification the different types of...
A relation between choosability and uniquely list colorability
, Article Journal of Combinatorial Theory. Series B ; Volume 96, Issue 4 , 2006 , Pages 577-583 ; 00958956 (ISSN) ; Mirrokni, V. S ; Sadjad, B. S ; Sharif University of Technology
2006
Abstract
Let G be a graph with n vertices and m edges and assume that f : V ( G ) → N is a function with ∑v ∈ V ( G ) f ( v ) = m + n. We show that, if we can assign to any vertex v of G a list Lv of size f ( v ) such that G has a unique vertex coloring with these lists, then G is f-choosable. This implies that, if ∑v ∈ V ( G ) f ( v ) > m + n, then there is no list assignment L such that | Lv | = f ( v ) for any v ∈ V ( G ) and G is uniquely L-colorable. Finally, we prove that if G is a connected non-regular multigraph with a list assignment L of edges such that for each edge e = u v, | Le | = max { d ( u ), d ( v ) }, then G is not uniquely L-colorable and we conjecture that this result holds for...
Kr-free uniquely vertex colorable graphs with minimum possible edges
, Article Journal of Combinatorial Theory. Series B ; Volume 82, Issue 2 , 2001 , Pages 316-318 ; 00958956 (ISSN) ; Mirrokni, V. S ; Sadjad, B. S ; Sharif University of Technology
2001
Abstract
We construct counterexamples to the conjecture of Xu (1990, J. Combin. Theory Ser. B50, 319-320) that every uniquely r-colorable graph of order n with exactly (r-1)n-(r2) edges must contain a Kr. © 2001 Academic Press
Synthesis and characterization of nanocrystalline barium strontium titanate
, Article Materials Science- Poland ; Volume 28, Issue 2 , 2010 , Pages 421-426 ; 01371339 (ISSN) ; Nemati, Z. A ; Faghihi Sani, M. A ; Sharif University of Technology
2010
Abstract
Barium strontium titanate (BST) was prepared via the simple sol-gel method by using tetrabutyl ti-tanate, ethanol, citric acid and ethylene glycol as starting materials. Thermogravimetry and differential thermal analysis were used to examine the behaviour of the xerogel. The particle size of BST was approximately 21 nm, as calculated by the X-ray diffraction and confirmed by transition electron microscopy for the calcination temperature of 750 °C. It was found that the particles of BST powders calcined at 750 °C were smaller and more homogeneous and uniform than those obtained at 800 °C
Microstructural developments and electrical properties of novel coarse-grained SnO2 varistors obtained by CuO addition for low-voltage applications
, Article Ceramics International ; Volume 44, Issue 15 , 2018 , Pages 18478-18483 ; 02728842 (ISSN) ; Mahmoudi, P ; Golmohammad, M ; Delshad Chermahini, M ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
This research focused on making novel low-voltage SnO2 varistors by CuO addition on conventional high-voltage SnO2 varistors. Moreover, the withstand surge capability of samples was studied. The results showed that CuO addition enhances grain growth of SnO2 and coarse-grained SnO2 varistors with simple microstructures were acquired in 1 mol% CuO-doped sample. This coarse-grained SnO2 varistor presented a high nonlinear coefficient (23) and low leakage current density (23 µA/cm2) with low breakdown field value of 0.6 kV/cm. Despite the large grain size, the low residual voltage ratio (2.3) was obtained for this sample compared to the CuO-free sample. The decrease in grain electric resistivity...
Synthesis and characterization of rGO/Fe2O3 nanocomposite as an efficient supercapacitor electrode material
, Article Journal of Materials Science: Materials in Electronics ; Volume 31, Issue 17 , 2020 , Pages 14998-15005 ; Nemati, A ; Malek Khachatourian, A ; Golmohammad, M ; Sharif University of Technology
Springer
2020
Abstract
The reduced graphene oxide-Fe2O3 (rGO-Fe2O3) nanocomposites were synthesized by a facile and low-cost hydrothermal method employing rGO and Iron (III) nitrate precursors. The synthesis parameters including the reduction time and presence of reduction aid are studied. The structural and morphological studies of the nanocomposites were investigated by using Raman spectra, Fourier transform infrared spectroscopy, X-ray diffraction, and field emission scanning electron microscopy. The results indicate that Fe2O3 nanoparticles with average particle size of 25 nm are well anchored on graphene sheets and the weight percent of the nanoparticles in the nanocomposites was influenced by the reduction...
Synthesis of Sr3Fe2O7and Investigation of the Effect of Pr in Sr Site and Co in Fe Site as a Dopant on the Microstructure and its Function as a Solid Oxide Fuel Cathode
, M.Sc. Thesis Sharif University of Technology ; Nemati, Ali (Supervisor) ; Golmohammad, Mohammad (Supervisor)
Abstract
Nowday, one of the important goals of researchers is to develop and improve the properties of intermediate tempreture solid oxide fuel cells with range of 600-800˚C. Therefore, choosing the right material as a cathode with good performance in this temperature range is very important. For this purpose, various materials with ionic and electron conductivity mixtures (MIECs) are used, especially oxides with a Radelsden-Paper structure. These oxides are shown by the formula An+1BnC3n+1, which are actually composed of a combination of perovskite layers (ABO3) that are alternately superimposed between two layers of rock salt (AO). In the present study, Sr3Fe2O7 powder with different amounts...
Uniquely 2-list colorable graphs
, Article Discrete Applied Mathematics ; Volume 119, Issue 3 , 2002 , Pages 217-225 ; 0166218X (ISSN) ; Ghebleh, M ; Hajiabolhassan, H ; Mirzazadeh, M ; Sadjad, B. S ; Sharif University of Technology
2002
Abstract
A graph is said to be uniquely list colorable, if it admits a list assignment which induces a unique list coloring. We study uniquely list colorable graphs with a restriction on the number of colors used. In this way, we generalize a theorem which characterizes uniquely 2-list colorable graphs. We introduce the uniquely list chromatic number of a graph and make a conjecture about it which is a generalization of the well-known Brooks' theorem. © 2002 Elsevier Science B.V
The effect of doping Bi2O3 on sintering temperature, microstructure, electrical nonlinearity and stability of high-voltage SnO2 varistors
, Article Journal of Materials Science: Materials in Electronics ; Volume 34, Issue 15 , 2023 ; 09574522 (ISSN) ; Mahmoudi, P ; Golmohammad, M ; Akbarpour, M. R ; Sohrabi, N ; Sharif University of Technology
Springer
2023
Abstract
One of the significant drawbacks of SnO2 varistors compared to their old counterpart, ZnO varistors, in high-voltage applications is their higher sintering temperature. Although the researchers have been attempting to lower the sintering temperature by employing new techniques, the obtained varistors do not show an acceptable capability to absorb surge currents. In this research, by optimizing the Bi2O3 amount added to the well-known SnO2 varistor system, the sintering temperature of varistors reduced to 1250 °C. It is for the first time that the reduction in sintering temperature of SnO2 varistors was accompanied not only with maintaining the nonlinearity of the obtained varistors, but also...
The effect of phosphorus and nitrogen dopants on structural, microstructural, and electrochemical characteristics of 3D reduced graphene oxide as an efficient supercapacitor electrode material
, Article Diamond and Related Materials ; Volume 137 , 2023 ; 09259635 (ISSN) ; Dehghani Mohammad Abadi, M ; Malek Khachatourian, A ; Golmohammad, M ; Nemati, A ; Sharif University of Technology
Elsevier Ltd
2023
Abstract
Supercapacitors are environmentally friendly and safe energy storage devices for diverse applications. The electrode material's structural, microstructural, and electrochemical properties are crucial determinants of supercapacitor capacity. One effective method to improve electrode performance is introducing doping heteroatoms or synthesizing composite materials. In this study, three-dimensional reduced graphene oxide (3D rGO) doped with Phosphorus, Nitrogen, or both (N/P co-doped) was synthesized for high-efficiency, supercapacitors using a facile, fast, and cost-effective hydrothermal process. The hydrothermal reduction of graphene oxide involved substituting Phosphorus and Nitrogen...
Fabrication and characterization of KNN Piezoelectrics
, M.Sc. Thesis Sharif University of Technology ; Khachatourian, Adrineh Malek (Supervisor) ; Golmohammad, Mohammad (Supervisor)
Abstract
Due to the environmental problems of lead and the prohibition of its use, lead-free piezoceramic sodium-potassium niobate, KNN, are one of the main candidates to replace lead-containing piezoceramics, PZTs. High Curie temperature, low density, and compatibility with nickel electrodes are its distinguishing features from other piezoelectric materials. The crystal structure of this material varies with temperature and includes rhombohedral, orthorhombic, tetragonal, and cubic. Various synthesis and manufacturing methods including hydrothermal, solid-state reaction, sol-gel, molten salt, etc. are used for this material. In this research, the hydrothermal synthesis method is used due to its high...
Basic requirements for a teamwork in middle size RoboCup
, Article 5th Robot World Cup Soccer Games and Conferences, RoboCup 2001, Seattle, WA, 2 August 2001 through 10 August 2001 ; Volume 2377 LNAI , 2002 , Pages 621-626 ; 03029743 (ISSN); 3540439129 (ISBN); 9783540439127 (ISBN) ; Chitsaz, H ; Foroughnassirai, A ; Ghorbani, R ; Kazemi, M ; Mirrokni, V. S ; Sadjad, B. S ; Sharif University of Technology
Springer Verlag
2002
Abstract
In this paper we describe some mechanical, hardware and software aspects of our robots specially used in teamwork. The pneumatic design of the gripers and kicker enables the robot to make a good control of ball when dribbling and also passing the ball in short and long distances. The teamwork software enables our robots to perform a cooperative behavior by dividing the field to three major regions and assigning each robot a role such as defender, forward and middle in these three regions. The server can order the robots to change their role when needed and make them return to their original state after a short time. © 2002 Springer-Verlag Berlin Heidelberg
Middle sized soccer robots: ARVAND
, Article 3rd Robot World Cup Soccer Games and Conferences, RoboCup 1999, 27 July 1999 through 6 August 1999 ; Volume 1856 , 2000 , Pages 61-73 ; 03029743 (ISSN); 9783540410430 (ISBN) ; Foroughnassiraei, A ; Chiniforooshan, E ; Ghorbani, R ; Kazemi, M ; Chitsaz, H ; Mobasser, F ; Sadjad, S. B ; Sony Corporation ; Sharif University of Technology
Springer Verlag
2000
Abstract
Arvand is the name of robots specially designed and con-structed by sharif CE team for playing soccer according to RoboCup rules and regulations for the middle size robots. Two different types of robots are made, players and the goal keeper. A player robot consists of three main parts: mechanics (motion mechanism and kicker), hard-ware (image acquisition, processing unit and control unit) and software (image processing, wireless communication, motion control and decision making). The motion mechanism is based on two drive unit, two steer units and a castor wheel. We designed a special control board which uses two microcontrollers to carry out the software system decisions and transfers them...
Design and construction of a soccer player robot ARVAND
, Article 3rd Robot World Cup Soccer Games and Conferences, RoboCup 1999, 27 July 1999 through 6 August 1999 ; Volume 1856 , 2000 , Pages 745-749 ; 03029743 (ISSN); 9783540410430 (ISBN) ; Foroughnassiraei, A ; Chiniforooshan, E ; Ghorbani, R ; Kazemi, M ; Chitsaz, H ; Mobasser, F ; Sadjad, S. B ; Sony Corporation ; Sharif University of Technology
Springer Verlag
2000
Abstract
Arvand is a robot specially designed and constructed for playing soccer according to RoboCup rules and regulations for the medium size robots. This robot consists of three main parts: mechanics (motion mechanism and kicker), hardware (image acquisition, processing unit and control unit) and software (image processing, wireless communication, motion control and decision making). The motion mechanism is based on a drive unit, a steer unit and a castor wheel. We designed a special control board which uses two microcontrollers to carry out the software system decisions and transfers them to the robot mechanics. The software system written in C++ performs real time image processing and object...