Alireza Bagheri - Academia.edu (original) (raw)

Papers by Alireza Bagheri

arXiv (Cornell University), Apr 4, 2019

Given two point sets S and T on a line, we present the first linear time algorithm for finding th... more Given two point sets S and T on a line, we present the first linear time algorithm for finding the limited capacity many-to-many matching (LCMM) between S and T improving the previous best known quadratic time algorithm. The aim of the LCMM is to match each point of S (T) to at least one point of T (S) such that the matching costs is minimized and the number of the points matched to each point is limited to a given number.

arXiv (Cornell University), Apr 9, 2019

Given two point sets S and T , the minimum-cost many-to-many matching with demands (MMD) problem ... more Given two point sets S and T , the minimum-cost many-to-many matching with demands (MMD) problem is the problem of finding a minimum-cost many-to-many matching between S and T such that each point of S (respectively T) is matched to at least a given number of the points of T (respectively S). We propose the first O n 2 time algorithm for computing a one dimensional MMD (OMMD) of minimum cost between S and T , where |S| + |T | = n. In an OMMD problem, the input point sets S and T lie on the real line and the cost of matching a point to another point equals the distance between the two points. We also study a generalized version of the MMD problem, the many-to-many matching with demands and capacities (MMDC) problem, that in which each point has a limited capacity in addition to a demand. We give the first O(n 2) time algorithm for the minimum-cost one dimensional MMDC (OMMDC) problem.

arXiv (Cornell University), Aug 19, 2017

A hidden guard set G is a set of point guards in polygon P that all points of the polygon are vis... more A hidden guard set G is a set of point guards in polygon P that all points of the polygon are visible from some guards in G under the constraint that no two guards may see each other. In this paper, we consider the problem for finding minimum hidden guard sets in histogram polygons under orthogonal visibility. Two points p and q are orthogonally visible if the orthogonal bounding rectangle for p and q lies within P. It is known that the problem is NP-hard for simple polygon with general visibility and it is true for simple orthogonal polygon. We proposed a linear time exact algorithm for finding minimum hidden guard set in histogram polygons under orthogonal visibility. In our algorithm, it is allowed that guards place everywhere in the polygon.

Nowadays, identification and detection community structures in complex networks is an important f... more Nowadays, identification and detection community structures in complex networks is an important factor in extracting useful information from networks. Label propagation algorithm with near linear-time complexity is one of the most popular methods for detecting community structures, yet its uncertainty and randomness is a defective factor. Merging LPA with other community detection metrics would improve its accuracy and reduce instability of LPA. Considering this point, in this paper we tried to use edge betweenness centrality to improve LPA performance. On the other hand, calculating edge betweenness centrality is expensive, so as an alternative metric, we try to use local edge betweenness and present LPA-LEB (Label Propagation Algorithm Local Edge Betweenness). Experimental results on both real-world and benchmark networks show that LPA-LEB possesses higher accuracy and stability than LPA when detecting community structures in networks.

Artificial intelligence review, Feb 14, 2024

The creation and propagation of disinformation on social media is a growing concern. The widespre... more The creation and propagation of disinformation on social media is a growing concern. The widespread dissemination of disinformation can have destructive effects on people's attitudes and behavior. So, it is essential to detect disinformation as soon as possible. Therefore, the interest in effective detection techniques has grown rapidly in recent years. Major social media and social networking sites are trying to develop robust strategies to detect disinformation and prevent its spread. Machine learning techniques and especially neural networks, have an essential role in this task. In this paper, we review different approaches for automatic disinformation detection, with a focus on methods that leverage graph neural networks (GNNs). GNNs are very suitable tools for detecting disinformation in social networks. Because on the one hand, graphs are the most comprehensive way to model social networks and on the other hand, GNNs are the best tool for processing graph data. We define different forms of disinformation, and examine the features used and the methods presented from different perspectives. We also discuss relevant research areas, open problems, and future research directions for disinformation detection in social media.

The Freeze Tag Problem (FTP) aims at awakening a swarm of robots with one or more initial awake r... more The Freeze Tag Problem (FTP) aims at awakening a swarm of robots with one or more initial awake robots as soon as possible. Each awake robot must touch an sleeping robot to awake it. Once a robot is awakened, it can assist in awakening other sleeping robots. We study this problem inside a polygonal domain and present approximation algorithms for it.

arXiv (Cornell University), Aug 4, 2017

Given an orthogonal polygon P with n vertices, the goal of the watchman route problem is finding ... more Given an orthogonal polygon P with n vertices, the goal of the watchman route problem is finding a path S of the minimum length in P such that every point of the polygon P is visible from at least one of the point of S. In the other words, in the watchman route problem we must compute a shortest watchman route inside a simple polygon of n vertices such that all the points interior to the polygon and on its boundary are visible to at least one point on the route. If route and polygon be orthogonal, it is called orthogonal watchman route problem. One of the targets of this problem is finding the orthogonal path with the minimum number of bends as possible. We present a linear-time algorithm for the orthogonal watchman route problem, in which the given polygon is monotone. Our algorithm can be used also for the problem on simple orthogonal polygons P for which the dual graph induced by the vertical decomposition of P is a path, which is called path polygon.

ArXiv, 2017

We are interested in the problem of guarding simple orthogonal polygons with the minimum number o... more We are interested in the problem of guarding simple orthogonal polygons with the minimum number of $ r −guards.Theinteriorpoint-guards. The interior point −guards.Theinteriorpoint p $ belongs an orthogonal polygon $ P $ is visible from $ r −guard-guard −guard g ,iftheminimumarearectanglecontained, if the minimum area rectangle contained ,iftheminimumarearectanglecontained p $ and $ q $ lies within $ P .Asetofpointguardsinpolygon. A set of point guards in polygon .Asetofpointguardsinpolygon P $ is named guard set (as denoted $ G )iftheunionofvisibilityareasofthesepointguardsbeequaltopolygon) if the union of visibility areas of these point guards be equal to polygon )iftheunionofvisibilityareasofthesepointguardsbeequaltopolygon P $ i.e. every point in $ P $ be visible from at least one point guards in $ G .Foranorthogonalpolygon,ifdualgraphofverticaldecompositionisapath,itisnamedpathpolygon.Inthispaper,weshowthattheproblemoffindingtheminimumnumberof. For an orthogonal polygon, if dual graph of vertical decomposition is a path, it is named path polygon. In this paper, we show that the problem of finding the minimum number of .Foranorthogonalpolygon,ifdualgraphofverticaldecompositionisapath,itisnamedpathpolygon.Inthispaper,weshowthattheproblemoffindingtheminimumnumberof r −guards(minimumguardset)becomeslinear−timesolvableinorthogonalpathpolygons.Thepathpolygonmayhavedentedgesineveryfourorientations.Forthisclassoforthogonalpolygon,theproblemhasbeenconsideredbyWormanandKeilwhodescribedanalgorithmrunningin-guards (minimum guard set) becomes linear-time solvable in orthogonal path polygons. The path polygon may have dent edges in every four orientations. For this class of orthogonal polygon, the problem has been considered by Worman and Keil who described an algorithm running in −guards(minimumguardset)becomeslinear−timesolvableinorthogonalpathpolygons.Thepathpolygonmayhavedentedgesineveryfourorientations.Forthisclassoforthogonalpolygon,theproblemhasbeenconsideredbyWormanandKeilwhodescribedanalgorithmrunningin O(n^{17} poly\l...

International Journal of Scientific & Technology Research, 2014

Covering the set of points with a geometric shape is an important problem in computational geomet... more Covering the set of points with a geometric shape is an important problem in computational geometry. In this problem, given a set of points in the plane of total size n and a geometric shape, covering the points with the geometric shape with minimum perimeter or area is the goal. The points may have different colors or divided into desirable and non-desirable points. On the other hand, in the separability problem, it is required that all of the desirable points lay inside the geometric shape and all of the other lay outside it. There has been a fair amount of work on different kinds of separators such as rectangles, squares, circles, etc. In this paper, a new algorithm based on genetic algorithm is presented for finding the maximum monochromatic polygon, which contains the maximum number of desirable points while avoids non-desirable points. Finding the maximum monochromatic polygon is an important problem in computational geometry which has many applications in different fields. Al...

Innovaciencia Facultad de Ciencias Exactas Físicas y Naturales, 2019

The separation of color points is one of the important issues in computational geometry, which is... more The separation of color points is one of the important issues in computational geometry, which is used in various parts of science; it can be used in facility locating, image processing and clustering. Among these, one of the most widely used computational geometry in the real-world is the problem of covering and separating points with rectangles. In this paper, we intend to consider the problemof separating the two-color points sets, using three rectangles. In fact, our goal is to separate desired blue points from undesired red points by three rectangles, in such a way that these three rectangles contain the most desire points. For this purpose, we provide a metaheuristic algorithm based on the simulated annealing method that could separates blue points from input points, , in time order O (n) with the help of three rectangles. The algorithm is executed with C# and also it has been compared and evaluated with the optimum algorithm results. The results show that our recommended algo...

International Journal of Computer Applications, 2016

Today`s, cloud computing has been widely accepted in the industry. With the increasing popularity... more Today`s, cloud computing has been widely accepted in the industry. With the increasing popularity of cloud computing, many users and companies want to use and offer cloud computing services. The growth of cloud computing services may lead to consume a huge amount of energy and emit considerable amount of carbon dioxide. In recent years raising concerns about global warming and environment impact of greenhouse gases emission has led many researchers to engage in research in the field of green and energy aware computing. In this paper, "two phase carbon aware cloud broker" has been proposed that attempt to minimize energy and carbon by considering the energy and carbon efficiency of data centers.

Journal of Mathematics

A many-to-many matching (MM) between two sets matches each element of one set to at least one ele... more A many-to-many matching (MM) between two sets matches each element of one set to at least one element of the other set. A general case of the MM is the many-to-many matching with demands and capacities (MMDC) satisfying given lower and upper bounds on the number of elements matched to each element. In this article, we give a polynomial-time algorithm for finding a minimum-cost MMDC between two sets using the well-known Hungarian algorithm.

In this paper, a polyline grid drawing of free trees on two dimensional grids, bounded by simple ... more In this paper, a polyline grid drawing of free trees on two dimensional grids, bounded by simple polygons, is investigated. To the authors' knowledge, this is the rst attempt made to develop algorithms for drawing graphs on two dimensional grids bounded by simple polygons.

Given an undirected planar graph G with n vertices and a set S of n points inside a simple polygo... more Given an undirected planar graph G with n vertices and a set S of n points inside a simple polygon P , a point-set embedding of G on S is a planar drawing of G such that each vertex is mapped to a distinct point of S and the edges are polygonal chains surrounded by P. A special case of the embedding problem is that in which G is a balanced binary tree. In this paper, we present a new algorithm for embedding an n-vertex balanced binary tree BBT on a set S of n points inside a simple m-gon P in O(m 2 + nlog 2 n + mn) time with at most O(m) bends per edge.

With the advent of Web 2, the required platform for commenting and sharing it in web space was pr... more With the advent of Web 2, the required platform for commenting and sharing it in web space was provided for users, and it became a part of the daily activities of the users in cyberspace. Besides that, the emergence of social networks and boom of these networks intensified these activities, and today users' comments are frequently found in cyberspace. Unlike the past, users can easily express their views on political, sporting, or economic events, or they can even comment on a commodity they have bought and share their satisfaction or dissatisfaction of the purchased goods and make it available to other users. Today, prior to buying a product, every person looks for the comments of those who have purchased and used this product. All these reveal the importance of opinion mining field. Opinion mining (OM) area looks for a way to classify these comments. This is because due to the high volume of these opinions, one cannot manually review and sum up these comments, and the advantag...

Enterprise Architecture (EA) is a framework for description, coordination and alignment of all ac... more Enterprise Architecture (EA) is a framework for description, coordination and alignment of all activities across the organization in order to achieve strategic goals using ICT enablers. A number of EA-compatible frameworks have been developed. We, in this paper, mainly focus on Federal Enterprise Architecture Framework (FEAF) since its reference models are plentiful. Among these models we are interested here in its business reference model (BRM). The test process is one important subject of an EA project which is to somewhat overlooked. This lack of attention may cause drawbacks or even failure of an enterprise architecture project. To address this issue we intend to use International Software Testing Qualification Board (ISTQB) framework and standard test suites to present a method to improve EA testing process. The main challenge is how to communicate between the concepts of EA and ISTQB. In this paper, we propose a method for integrating these concepts.

Advances in Computer Science : an International Journal, 2014

Motion and locomotion planning have a wide area of usage in different fields. Locomotion planning... more Motion and locomotion planning have a wide area of usage in different fields. Locomotion planning with premade character animations has been highly noticed in recent years. Reinforcement Learning presents promising ways to create motion planners using premade character animations. Although RL-based motion planners offer great ways to control character animations but they have some problems that make them hard to be used in practice, including high dimensionality and environment dependency. In this paper we present a motion planner which can fulfill its motion tasks by selecting its best animation sequences in different environments without any previous knowledge of the environment. We combined reinforcement learning with a fuzzy motion planer to fulfill motion tasks. The fuzzy control system commands the agent to seek the goal in environment and avoid obstacles and based on these commands, the agent select its best animation sequences. The motion planner is taught through a reinforc...

ArXiv, 2019

Given two point sets S and T, a many-to-many matching with demands (MMD) problem is the problem o... more Given two point sets S and T, a many-to-many matching with demands (MMD) problem is the problem of finding a minimum-cost many-to-many matching between S and T such that each point of S (respectively T) is matched to at least a given number of the points of T (respectively S). We propose the first O(n^2) time algorithm for computing a one dimensional MMD (OMMD) of minimum cost between S and T, where |S|+|T| = n. In an OMMD problem, the input point sets S and T lie on the real line and the cost of matching a point to another point equals the distance between the two points. We also study a generalized version of the MMD problem, the many-to-many matching with demands and capacities (MMDC) problem, that in which each point has a limited capacity in addition to a demand. We give the first O(n^2) time algorithm for the minimum-cost one dimensional MMDC (OMMDC) problem.

2010 2nd International Conference on Software Technology and Engineering, 2010

Scheduling system of low earth orbit (LEO) satellite operations is one of the important tasks per... more Scheduling system of low earth orbit (LEO) satellite operations is one of the important tasks performed in satellites. Satellite specific constraints, satellite priorities, priorities of certain payload and special operations, as well as visibility conflicts are taken into consideration while generating the operations schedules in an optimum way. This paper proposes a tabu search heuristic for earth observation satellite scheduling problem, where as earth observing operations have to be scheduled on several resources while respecting time constraint and taking the priorities of the operations into account with the objective of scheduling as many operations as possible within its time window. The computational results indicate that this approach is typically effective to generate a near optimal and feasible schedule for imaging operations of the satellite.

Scientia Iranica

Separation of desired objects from undesired ones is one of the most important problems in comput... more Separation of desired objects from undesired ones is one of the most important problems in computational geometry. It is tended to cover the desired objects by one or a couple of geometric shapes in a way that all of the desired objects are included by the covering shapes, while the undesired objects are excluded. We study separation of polylines by minimal triangles with a given fixed angle and present () O NlogNtime algorithm, where N is the number of all the desired and undesired polylines. By a minimal triangle, we mean a triangle in which all of its edges are tangential to the convex hull of the desired polylines. The motivation for studying this separation problem stems from that we need to separate bichromatic objects that are modeled by polylines not points in real life scenarios.