Swampland Program in String Theory and Its Consequences in Cosmology

, M.Sc. Thesis Sharif University of Technology Ahangar, Amir (Author) ; Faraji Astaneh, Amin (Supervisor)

Abstract

Not all effective theories in the low energy limit are compatible with quantum gravity. The goal of the swampland program is bringing the necessary criteria to test these effective theories and examine their compatibility with quantum gravity. This set of conjectures determines which theory is effective in the perspective of the self-consistent theory of quantum gravity which is actually string theory. A very important connection (through the swamp program) between high energy physics (UV) And the physics of the low energy limit (IR) can provide very important explanations for our questions. Among them are the cosmological constant problem in general relativity and the hierarchy problem in...

Liquid-liquid-liquid microextraction followed by HPLC with UV detection for quantitation of ephedrine in urine

, Article Journal of Separation Science ; Volume 31, Issue 18 , 2008 , Pages 3212-3217 ; 16159306 (ISSN) Bagheri, H ; Khalilian, F ; Ahangar, L. E ; Sharif University of Technology

2008

Abstract

Liquid-liquid-liquid microextraction (LLLME) in combination with HPLC and UV detection has been used as a sensitive method for the determination of ephedrine in urine samples. Extraction process was performed in a homemade total glass vial without using a Teflon ring, usually employed. Ephedrine was first extracted from 3.5 mL of urine sample (pH 12) into a microfilm of toluene/benzene (50:50). The analyte was subsequently back extracted into an acidic microdrop solution (pH 2) suspended in the organic phase. The extract was then injected into the HPLC system directly. An enrichment factor of 137 along with a good sample clean-up was obtained under the optimized conditions. The calibration...

Identification of Reaction Wheel Disturbance and its impact on Attitude Determination Enhancement for Satellites with Magnetometer Sensors

, M.Sc. Thesis Sharif University of Technology Ahangar Parvin, Mohammad Mahdi (Author) ; Pourtakdoust, Hossein (Supervisor)

Abstract

The attitude determination (AD) and control system (ADCS) tasks in an operational satellite includes attitude determination, stabilization and pointing against internal and external disturbance moments. Where these tasks are carried out using several sensors, actuators as well as some pertinent attitude determination algorithms. In this sense, the magnetometer (MAG) sensor is among the most common sensors used to attitude estimation that can be utilized in association of reaction wheels (RWs) as a reliable and efficient actuation mechanism for a three-axis attitude control satellite. Unfortunately, RWs generate magnetic field disturbances during operation as commanded by ADCS that adversely...

Bioregeneration of Granular activated carbon (GAC) contaminated with phenolic compounds

, M.Sc. Thesis Sharif University of Technology Ahangar, Ata Ollah (Author) ; Vossoughi, Manouchehr (Supervisor) ; Borghei, Mehdi (Supervisor)

Abstract

This project surveys bioregeneration of granular activated carbons contaminated with phenolic compounds. To carry out this survey, the procedure of phenol absorption on the surface of activated carbon was studied and their adsorption isotherms were calculated. In the first step, newly activated carbon was contaminated with phenol solution and optimum amount of carbon in phenol elimination was 0.5g. Then, the effect of time contact on phenol elimination was studied and eventually 1 hour of time contact was determined as the equilibrium time of phenol adsorption. In the second step, kinetics of adsorption of phenol and different stages of adsorption were studied. The results of this study...

Synthesis of Bone graft Substitute for Clinical Applications

, M.Sc. Thesis Sharif University of Technology Khodabakhshi Tabar Ahangar, Zahra (Author) ; Abdekhodaie, Mohammad Jafar (Supervisor)

Abstract

The natural tissue of the bones consists of organic and inorganic parts. The bone mineral part contains calcium phosphate and its organic part is mainly of collagen fibers. The combination of these fibers and calcium phosphate makes the bone flexible and resistant to stresses. Many conditions, including osteoporosis and crashes, lead to fractures and cavities in bone. Bone cements are the most used materials used in orthopedic surgeries and spinal cord.The purpose of this study was to synthesis acrylic bone cement with properties determined by ASTM F 451 and Iso5833 for orthopedic applications, including joint replacement. Polymethyl methacrylate polymer was synthesized as the main component...

Factors influencing adoption of e-payment systems: an empirical study on Iranian customers

, Article Information Systems and e-Business Management ; Volume 15, Issue 1 , 2017 , Pages 89-116 ; 16179846 (ISSN) Barkhordari, M ; Nourollah, Z ; Mashayekhi, H ; Mashayekhi, Y ; Ahangar, M. S ; Sharif University of Technology

Springer Verlag 2017

Abstract

Internet technology has influenced the banking systems because of its capability to enhance performance of financial operations. A major concern of Internet banking systems is the customers’ perception of security and trust. This study presents an experimental investigation on important factors influencing trust in e-payments systems in Iran. A set of potentially determinant factors of trust is developed and organized in three major groups: technical and transaction procedures, access to security guidelines, and usability. The direct effect of the factors on perceived trust, along with their indirect effect through perceived security, is evaluated in an empirical study. The data are...

A general model for I/O system theory, Proceedings of AIMC31 [electronic resource]

, Article Iranian Journal of Fuzzy Systems ; 2006, Volume 3, Issue 2, Page 1-19 Daneshgar, A. (Amir) ; Hashem, Amir ; Sharif University of Technology

Hole transport material based on modified N-annulated perylene for efficient and stable perovskite solar cells

, Article Solar Energy ; Volume 194 , 2019 , Pages 279-285 ; 0038092X (ISSN) Sheibani, E ; Amini, M ; Heydari, M ; Ahangar, H ; Keshavarzi, R ; Zhang, J ; Mirkhani, V ; Sharif University of Technology

Elsevier Ltd 2019

Abstract

N-annulated perylene based materials show outstanding and tunable optical and physical properties, making them suitable to be charge transport materials for optoelectronic applications. However, this type of materials has so far not been well studied in solar cells. Here, we develop a new hole transport material (HTM), namely S5, based on perylene building block terms, for organic-inorganic hybrid perovskite solar cells (PSCs). We have systematically studied the influences of the film thickness of S5 on their photovoltaic performance, and a low concentration of S5 with a thinner HTM film is favorable for obtaining higher solar cell efficiency. S5 shows excellent energy alignment with...

Experimental and Numerical Study of Spray Combustion under Hot-diluted Conditions

, M.Sc. Thesis Sharif University of Technology Azimi, Amir Hossein (Author) ; Mardani, Amir (Supervisor)

Abstract

In this thesis, combustion of liquid fuel spray under the condition of hot and diluted oxidizer, has been investigated. To this end, a novel type laboratory-scale test rig was designed to study the physics governing the MILD-Spray combustion conditions with an applied approach. The underlined test rig eliminates the operational problems of its predecessor test stands and is used for a heavier fuel with much more complex chemical composition (kerosene). The test section is axially symmetrical, in which the fuel is injected by a pressure-swirl atomizer in the direction of hot and diluted co-flowing air. With the use of the aforesaid test rig, the effect of variables such as oxygen...

3D asymmetric carbozole hole transporting materials for perovskite solar cells

, Article Solar Energy ; Volume 189 , 2019 , Pages 404-411 ; 0038092X (ISSN) Sheibani, E ; Heydari, M ; Ahangar, H ; Mohammadi, H ; Taherian Fard, H ; Taghavinia, N ; Samadpour, M ; Tajabadi, F ; Sharif University of Technology

Elsevier Ltd 2019

Abstract

Carbazole compounds are p-type hole-transporting materials (HTMs) useful for perovskite solar cells (PSCs). In this work, we developed a new class of carbazol based HTMs; non-fused 3-D asymmetric structures (S14 and S12) as HTM of PSCs. To the best of our knowledge, there is no report on non-fused HTMs with a high glass transition temperature (Tg = 165 °C), which reduces crystallization and suppresses grain boundaries in glassy film, resulting in long-term durability. Experimental results show that tuning the carbazole moiety in S14 structure has a constructive influence on geometrical alignment, hole mobility, hydrophobicity, stability as well as efficiency. The resultant power conversion...

General theory of translation invariant systems [electronic resource]

, Article Mathematics and Its Applications ; Volume 329, 1995, pp 77-89 Daneshgar, A. (Amir) ; Sharif University of Technology

Abstract

The basic goal of this article is to present an abstract system-theoretic approach to morphological filtering and the theory of translation invariant systems which is mainly based on residuated semigroups. Some new results as well as a number of basic questions are also introduced

Duality in a generalized model for translation invariant systems [electronic resource]

, Article Fuzzy Sets and Systems ; 1996, Volume 83, Issue 3, Pages 347–352 Daneshgar, A. (Amir) ; Sharif University of Technology

Abstract

In a previous paper we introduced a generalized model for translation invariant (TI) operators. In this model we considered the space, φ of all maps from an abelian group G to ω U {-∞}, called LG-fuzzy sets, where ω is a complete lattice-ordered group; and we defined TI operators on this space. Also, in that paper, we proved strong reconstruction theorem to show the consistency of this model. This theorem states that for an order-preserving TI operator Y one can explicitly compute Y(A), for any A, from a specific subset of φ called the base of Y. In this paper duality is considered in the same general framework, and in this regard, continuous TI operators are studied. This kind of operators...

Reconstruction in a generalized model for translation invariant systems [electronic resource]

, Article Fuzzy Sets and Systems ; 1996, Volume 83, Issue 1, Pages 51–55 Daneshgar, A. (Amir) ; Sharif University of Technology

Abstract

We consider translation invariant (TI) operators on Φ, the set of maps from an abelian group G to Ω ∪ {−∞} , called LG-fuzzy sets, where 0 is a complete lattice ordered group. By defining Minkowski and morphological operations on Φ and considering order preserving operators, we prove a reconstruction theorem. This theorem, which is called the Strong Reconstruction Theorem (SRT), is similar to the Convolution Theorem in the theory of linear and shift invariant systems and states that for an order preserving TI operator Y one can explicitly compute Y ( A ), for any A , from a specific subset of Φ called the base of Y . The introduced framework is a general model for the theory of translation...

Residuated semigroups and morphological aspects of translation invariant systems [electronic resource]

, Article 1997, Volume 90, Issue 1, Pages 69–81 ; Fuzzy Sets and Systems Daneshgar, A. (Amir) ; Sharif University of Technology

Abstract

The main goal of this paper is to verify classical properties of morphological operators within the general model of translation invariant (TI) systems. In this model, TI operators are defined on the space of LG-fuzzy sets Φ i.e. Φ = {A: G → Ω ∪ {− ∞}} in which G is an abelian group and Ω is a complete lattice ordered group. A TI operator Y is an operator on Φ which is invariant under translation on G and Ω as groups. We consider the generalization of Minkowski addition (D on Φ and we emphasize that (Φ,⊛) is an involutive residuated topological monoid. We verify all properties of traditional (set-theoretic) morphological operators as well as classical representations (Matheron, 1967) for...

Forcing structures and cliques in uniquely vertex colorable graphs [electronic resource]

, Article SIAM Journal on Discrete Mathematics ; 2001, Volume 14, Issue 4, Pages 433-445 Daneshgar, A. (Amir) ; Sharif University of Technology

Abstract

Let G be a simple undirected uniquely vertex k-colorable graph, or a k-UCG for short. M. Truszczyński [Some results on uniquely colorable graphs, in Finite and Infinite Sets, North-Holland, Amsterdam, 1984, pp. 733--748] introduced $e^{^{*}}(G)=|V(G)|(k-1)-{k \choose 2}$ as the minimum number of edges for a k-UCG and S. J. Xu [J. Combin. Theory Ser. B, 50 (1990), pp. 319--320] conjectured that any minimal k-UCG contains a Kk as a subgraph. In this paper, first we introduce a technique called forcing. Then by applying this technique in conjunction with a feedback structure we construct a k-UCG with clique number k-t, for each $t \geq 1$ and each k, when k is large enough. This also...

Graph homomorphisms and nodal domains [electronic resource]

, Article Linear Algebra and its Applications ; 2006, Volume 418, Issue 1, Pages 44–52 Daneshgar, A. (Amir) ; Sharif University of Technology

Abstract

In this paper, we derive some necessary spectral conditions for the existence of graph homomorphisms in which we also consider some parameters related to the corresponding eigenspaces such as nodal domains. In this approach, we consider the combinatorial Laplacian and co-Laplacian as well as the adjacency matrix. Also, we present some applications in graph decompositions where we prove a general version of Fisher’s inequality for G-designs

On defining numbers of circular complete graphs

, Article Discrete Mathematics ; Volume 307, Issue 2, 28 January 2007, Pages 173–180 Daneshgar, A. (Amir) ; Sharif University of Technology

Abstract

Let d(σ)d(σ) stand for the defining number of the colouring σσ. In this paper we consider View the MathML sourcedmin=minγd(γ) and View the MathML sourcedmax=maxγd(γ) for the onto χχ-colourings γγ of the circular complete graph Kn,dKn,d. In this regard we obtain a lower bound for dmin(Kn,d)dmin(Kn,d) and we also prove that this parameter is asymptotically equal to χ-1χ-1. Also, we show that when χ⩾4χ⩾4 and s≠0s≠0 then dmax(Kχd-s,d)=χ+2s-3dmax(Kχd-s,d)=χ+2s-3, and, moreover, we prove an inequality relating this parameter to the circular chromatic number for any graph G

Modeling Driving Behaviors Using Smartphone Sensors

, M.Sc. Thesis Sharif University of Technology Azizzadeh Delshad, Amir Hossein (Author) ; Samimi, Amir (Supervisor)

Abstract

Monitoring driving behaviors of drivers, would avoid their dangerous behaviors and remarkably raise the safety. Nowadays real-time supervision is considered as one of the modern methods of controlling driving behaviors. Previously, due to expensive costs of required equipments and other restrictions, this kind of supervision hasn't been considered fairly. Nowadays increasing usage of smart phones, which contain multiple sensors, enables this type of supervision with lower costs. In the present study we would present some models, to assess the driving behavior via smart phone sensors such as accelerometer, gyroscope and rotation vector

Crack Propagation Modeling in Arched Concrete Structures Reinforced by FRP Using XFEM and Damage Model

, M.Sc. Thesis Sharif University of Technology Mohammadi, Amir Hossein (Author) ; Khoei, Amir Reza (Supervisor)

Abstract

In practice, structures made of concrete are full of cracks. The strength of concrete is mainly determined by the tensile strength, which is about 10% of the compressive strength. As long as cracking in concrete is unavoidable, we have to try to minimize their detrimental effects. This objective can be achieved by resisting (or limiting) propagation of existing cracks. Because of this, reinforcement (mostly steel) is used to increase the carrying capacity of the material and to control the development of cracks. Concrete structures that fail, already shows a large number of large and small cracks before their maximum carrying capacity is reached. The failure of concrete can be characterized...

Structural Health Monitoring Using Optimal Finite Element Model Based on Digital Image Correlation

, M.Sc. Thesis Sharif University of Technology Amir Hossein Amir Ahmadi (Author) ; Khaloo, Alireza (Supervisor)

Abstract

The purpose of this research is to monitor the health of structures using the updated finite element model, in which digital images are used to optimize the numerical model. Structural Health Monitoring (SHM) is always an important and significant issue that has attracted the attention of many researchers in recent years. In general, some researches have been conducted in this field using physical sensors that provide discrete data to the system for analysis. Using cameras to monitor the structure makes it possible to extract continuous and integrated data from the structure using digital images, which is a significant advantage compared to physical sensors.In this research, a steel...