The densification behavior of metals and alloys during spark plasma sintering: A mini-review

, Article Science of Sintering ; Volume 51, Issue 2 , 2019 , Pages 1-18 ; 0350820X (ISSN) Sovizi, S ; Esmaeeli Seraji, M ; Sharif University of Technology

International Institute for the Science of Sintering (IISS) 2019

Abstract

As of today, metals and alloys are widely utilized as structural, mechanical, electrical, and magnetic materials in every aspect of technology and industry. The complexity and diversity of metals applications emphasize the need for a new production method to quickly and easily manufacture metallic components. Spark plasma sintering as a new solid-state sintering method has been recently developed to respond to these needs. Up to now, numerous papers and researches have been published in the field of spark plasma sintering and its ability to manufacture metallic samples. Density is a significant property that has a great influence on the physical, mechanical, and functional properties of...

Co-precipitation Synthesis Parameters of Lithium-rich Cathode Material

, M.Sc. Thesis Sharif University of Technology Seraji, Pardis (Author) ; Sadrnezhaad, Khatiboleslam (Supervisor)

Abstract

Electric vehicles and electronics such as laptops and smartphones require an efficient amount of energy conversion and storage. As one of the reliable systems in this field, lithium-ion batteries have high energy density and lower emissions. Cathodic material is a bottleneck in the development of lithium-ion systems due to its high cost and limited energy capacity. In this study, lithium-rich oxide cathode was synthesized in the liquid phase using the co-precipitation synthesis method using six-aqueous nickel nitrate and four-aqueous manganese chloride precursors. The material was analyzed by structural characterization analysis as well as electrochemical characterizations. In this project,...

Geodesic spanners for points in R3 amid axis-parallel boxes

, Article Information Processing Letters ; Volume 166 , 2021 ; 00200190 (ISSN) Abam, M. A ; Rezaei Seraji, M. J ; Sharif University of Technology

Elsevier B.V 2021

Abstract

Let P be a set of n points in R3 amid a bounded number of obstacles. Consider the metric space M=(P,dM) where dM(p,q) is the geodesic distance of p and q, i.e., the length of a shortest path from p to q avoiding obstacles. When obstacles are axis-parallel boxes, we prove that M admits an 83-spanner with O(nlog3⁡n) edges. In other words, let S be a complete graph on n vertices where each node corresponds to a point p∈P. For nodes u and v of S corresponding to p,q∈P, the edge (u,v) is associated with the geodesic distance of p and q as its weight. We indeed prove that S admits a near linear-size t-spanner for some constant t. © 2020 Elsevier B.V

Geodesic spanners for points in R3 amid axis-parallel boxes

, Article Information Processing Letters ; Volume 166 , 2021 ; 00200190 (ISSN) Abam, M. A ; Rezaei Seraji, M. J ; Sharif University of Technology

Elsevier B.V 2021

Abstract

Let P be a set of n points in R3 amid a bounded number of obstacles. Consider the metric space M=(P,dM) where dM(p,q) is the geodesic distance of p and q, i.e., the length of a shortest path from p to q avoiding obstacles. When obstacles are axis-parallel boxes, we prove that M admits an 83-spanner with O(nlog3⁡n) edges. In other words, let S be a complete graph on n vertices where each node corresponds to a point p∈P. For nodes u and v of S corresponding to p,q∈P, the edge (u,v) is associated with the geodesic distance of p and q as its weight. We indeed prove that S admits a near linear-size t-spanner for some constant t. © 2020 Elsevier B.V

Geodesic spanners for points on a polyhedral terrain

, Article SIAM Journal on Computing ; Volume 48, Issue 6 , 2019 , Pages 1796-1810 ; 00975397 (ISSN) Abam, M. A ; De Berg, M ; Rezaei Seraji, M. J ; Sharif University of Technology

Society for Industrial and Applied Mathematics Publications 2019

Abstract

Let S be a set of n points on a polyhedral terrain T in ℝ3, and let ϵ > 0 be a fixed constant. We prove that S admits a (2 + ϵ )-spanner with O(n log n) edges with respect to the geodesic distance. This is the first spanner with constant spanning ratio and a near-linear number of edges for points on a terrain. On our way to this result, we prove that any set of n weighted points in Rd admits an additively weighted (2 + ϵ )-spanner with O(n) edges; this improves the previously best known bound on the spanning ratio (which was 5 + ϵ ) and almost matches the lower bound. © 2019 Society for Industrial and Applied Mathematics Publications. All rights reserved

Geodesic spanners for points on a polyhedral terrain

, Article SIAM Journal on Computing ; Volume 48, Issue 6 , 2019 , Pages 1796-1810 ; 00975397 (ISSN) Abam, M. A ; De Berg, M ; Rezaei Seraji, M. J ; Sharif University of Technology

Society for Industrial and Applied Mathematics Publications 2019

Abstract

Let S be a set of n points on a polyhedral terrain T in ℝ3, and let ϵ > 0 be a fixed constant. We prove that S admits a (2 + ϵ )-spanner with O(n log n) edges with respect to the geodesic distance. This is the first spanner with constant spanning ratio and a near-linear number of edges for points on a terrain. On our way to this result, we prove that any set of n weighted points in Rd admits an additively weighted (2 + ϵ )-spanner with O(n) edges; this improves the previously best known bound on the spanning ratio (which was 5 + ϵ ) and almost matches the lower bound. © 2019 Society for Industrial and Applied Mathematics Publications. All rights reserved

Adaptive Lossless Image Compression of Pipelines in Smart Structures

, M.Sc. Thesis Sharif University of Technology Seraji, Amir (Author) ; Mortazavi, Mohammad (Supervisor) ; Ghorshi, Mohammad Ali (Supervisor)

Abstract

Structural Health Monitoring (SHM) means to give a diagnosis of the “state” of the subjects. Small leaks along the entire lengths of oil pipelines are detected and located by monitoring.Nowadays health monitoring of pipeline in water, gas, oil and chemical industry has been the focus of researchers. This is due to the fact that leak accidents may cause great economic problems to human resources as well as extreme environmental pollution. This project focuses on a visual and photographic observation system as leakage detection to monitor long range pipelines. In this system, several cameras with overlapping views are located along the entire lengths of pipelines. We are using digital cameras...

Online Conflict-free Coloring Of Intervals

, M.Sc. Thesis Sharif University of Technology Rezaei Seraji, Mohammad Javad (Author) ; Abam, Mohammad Ali (Supervisor)

Abstract

In this thesis, we consider the problem of online conflict-free coloring for regions. First, we analyze online variant of the conflict-free coloring of intervals on the line, where each newly inserted interval must be assigned a color upon insertion such that the coloring remains conflict-free, i.e. for every point p in the union of the current intervals, there must be an interval I with a unique color among all intervals covering p. we present deterministic algorithm for achieving this goal which uses O(log^3⁡n) color. Next, we consider the online conflict-free coloring of nearly-equal axis-parallel rectangles in the plane and present a deterministic algorithms which uses O(log^12⁡n)...

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

Geodesic spanners for points on a polyhedral terrain

, Article 28th Annual ACM-SIAM Symposium on Discrete Algorithms, SODA 2017, 16 January 2017 through 19 January 2017 ; 2017 , Pages 2434-2442 ; 9781611974782 (ISBN) Abam, M. A ; De Berg, M ; Rezaei Seraji, M. J ; Universitat Politecnica de Catalunya ; Sharif University of Technology

Association for Computing Machinery 2017

Abstract

Let S be a set S of n points on a polyhedral terrain T in R3, and let ϵ > 0 be a fixed constant. We prove that S admits a (2 + ϵ)-spanner with O(n log n) edges with respect to the geodesic distance. This is the first spanner with constant spanning ratio and a near-linear number of edges for points on a terrain. On our way to this result, we prove that any set of n weighted points in Rd admits an additively weighted (2 + ϵ)-spanner with O(n) edges; this improves the previously best known bound on the spanning ratio (which was 5 + ϵ), and almost matches the lower bound. Copyright © by SIAM

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...

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

The role of heat treatment on wear behavior of powder metallurgy low alloy steels

, Article Materials and Design ; Volume 23, Issue 7 , 2002 , Pages 667-670 ; 02641275 (ISSN) Khorsand, H ; Habibi, S. M ; Yoozbashizadea, H ; Janghorban, K ; Reihani, S. M. S ; Rahmani Seraji, H ; Ashtari, M ; Sharif University of Technology

Elsevier Ltd 2002

Abstract

The influence of manufacturing parameters such as compacting pressure, heat treatment and microstructure on the static and dynamic properties of Fe-1.75 Ni-1.5 Cu-0.5 Mo-0.6 C was investigated. Wear and fatigue tests were carried out on reciprocate wearing and tension compression mode, respectively. The results show that delamination wear mechanism of sintered steel is similar to that of conventional wrought or cast materials. But, in sintered material, open porosity acts as sites of generation and collection of wear debris or formation of subsurface cracks. Wear rate is decreased and fatigue strength is increased by heat treatment. © 2002 Elsevier Science Ltd. All rights reserved