Loading...
Search for:
voronoi
0.006 seconds
Total 24 records
A voronoi-based reactive approach for mobile robot navigation
, Article 13th International Computer Society of Iran Computer Conference on Advances in Computer Science and Engineering, CSICC 2008, Kish Island, 9 March 2008 through 11 March 2008 ; Volume 6 CCIS , 2008 , Pages 901-904 ; 18650929 (ISSN); 3540899847 (ISBN); 9783540899846 (ISBN) ; Hazar, N ; Sharif University of Technology
2008
Abstract
Robot navigation is a challenging problem in robotics, which involves determining of robot positioning relative to objects in the environment, and also the mobility of robot through obstacles without colliding into them. The former is known as localization, while the latter is called motion planning. This paper introduces a roadmap method for solving motion planning problem in a dynamic environment based on Generalized Voronoi Diagram (GVD). The efficiency of the proceeding work is verified by examining it in a sample home environment. © 2008 Springer-Verlag
Extended hexagonal constellations as a means of multicarrier PAPR reduction
, Article 1st EurAsian Conference on Advances in Information and Communication Technology, EurAsia-ICT 2002, Shiraz, 29 October 2002 through 31 October 2002 ; Volume 2510 LNCS , 2002 , Pages 926-936 ; 03029743 (ISSN); 3540000283 (ISBN); 9783540000280 (ISBN) ; Khalaj, B. H ; Sharif University of Technology
Springer Verlag
2002
Abstract
An efficient, easy to implement method for OFDM and DMT Peak to Average Power Ratio (PAPR) reduction is proposed based on constellation extension. A PAPR reduction of more than 5 dB at clip rate of 10-5, is achieved with no rate loss and improved noise margin with low complexity. Various versions of the proposed method have been studied and compared in terms of PAPR reduction, complexity and average power, with each other and earlier methods. © Springer-Verlag Berlin Heidelberg 2002
Continuous and discrete radius functions on voronoi tessellations and delaunay mosaics
, Article Discrete and Computational Geometry ; Volume 67, Issue 3 , 2022 , Pages 811-842 ; 01795376 (ISSN) ; Cultrera di Montesano, S ; Edelsbrunner, H ; Saghafian, M ; Sharif University of Technology
Springer
2022
Abstract
The Voronoi tessellation in Rd is defined by locally minimizing the power distance to given weighted points. Symmetrically, the Delaunay mosaic can be defined by locally maximizing the negative power distance to other such points. We prove that the average of the two piecewise quadratic functions is piecewise linear, and that all three functions have the same critical points and values. Discretizing the two piecewise quadratic functions, we get the alpha shapes as sublevel sets of the discrete function on the Delaunay mosaic, and analogous shapes as superlevel sets of the discrete function on the Voronoi tessellation. For the same non-critical value, the corresponding shapes are disjoint,...
Molecular Dynamics Study of Tungsten and Iron Addition on the Glass Formability of Cobalt-based Electrodeposited Coatings
, M.Sc. Thesis Sharif University of Technology ; Tavakoli, Rouhollah (Supervisor)
Abstract
Recent research suggests that the electrochemical deposition of cobalt-based binary alloys, such as cobalt-tungsten and cobalt-iron, can lead to the formation of amorphous structures in the coatings. Theoretical studies suggest that these structures are equivalent to structures created by the melt cooling of the alloy at speeds of about 〖10〗^10 Kelvin per second. The formation of a glass phase can significantly increase the abrasion resistance and corrosion resistance of these coatings. Empirical studies show that the ability of the glass to become glassy, or more precisely, the transition from crystalline to amorphous, is largely a function of the chemical composition. Simulation of...
Microstructure generation of severely deformed materials using Voronoi diagram in Laguerre geometry: Full algorithm
, Article Computational Materials Science ; Volume 50, Issue 9 , July , 2011 , Pages 2698-2705 ; 09270256 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
2011
Abstract
A new Voronoi diagram in Laguerre geometry based on closed-pack non-overlapping circles was proposed. This diagram was used to simulate microstructure of severely deformed materials at different applied strains. Grains size and their fractions were introduced by controlling the size and distribution of nuclei. Edge number distribution and neighboring cells edge number along with area distribution of the simulated Voronoi cells were determined. The edge number distribution was observed to fit gamma distribution more accurately. However, due to high inhomogeneity in the microstructure of the deformed samples at low strains, edge number distribution could not be matched by any distribution...
Molecular dynamics study of structural formation in Cu50-Zr50 bulk metallic glass
, Article Journal of Non-Crystalline Solids ; 2015 ; 00223093 (ISSN) ; Tavakoli, R ; Aashuri, H ; Sharif University of Technology
Elsevier
2015
Abstract
In this work, the evolution of the local structure in Cu50-Zr50 bulk metallic glass during glass formation was studied by molecular dynamics simulation. The pair distribution function and Voronoi analysis were adopted to characterize local structures in this alloy. The stability of icosahedral clusters and the role of other local clusters in the formation of icosahedra were evaluated. It was found that the (0,2,8,2) polyhedron is not only the dominant cluster in this alloy, but also the most prone cluster to convert into an icosahedron in the course of cooling. Moreover, it acts as an intermediate state during the icosahedron formation. The onset of stability of icosahedra emerges at the...
Molecular dynamics study of structural formation in Cu50–Zr50 bulk metallic glass
, Article Journal of Non-Crystalline Solids ; Volume 432 , 2016 , Pages 334-341 ; 00223093 (ISSN) ; Tavakoli, R ; Aashuri, H ; Sharif University of Technology
Elsevier B. V
2016
Abstract
In this work, the evolution of the local structure in Cu50–Zr50 bulk metallic glass during glass formation was studied by molecular dynamics simulation. The pair distribution function and Voronoi analysis were adopted to characterize local structures in this alloy. The stability of icosahedral clusters and the role of other local clusters in the formation of icosahedra were evaluated. It was found that the (0,2,8,2) polyhedron is not only the dominant cluster in this alloy, but also the most prone cluster to convert into an icosahedron in the course of cooling. Moreover, it acts as an intermediate state during the icosahedron formation. The onset of stability of icosahedra emerges at the...
Maximizing Payoff in Competitive Facility Location
, M.Sc. Thesis Sharif University of Technology ; Zarrabi Zadeh, Hamid (Supervisor)
Abstract
In the competitive facility location problem, two service providers fight over winning consumers by establishing a series of well-located facilities on the line. The consumers seek their required services from the facility which is closest to them. The order in which service providers locate and build their facilities is as follows: the first service provider establishes k facilities after which the second service provider locates another k facilities and this goes on for m rounds. The payoff of each service provider equals the number of consumers that choose that provider’s facilities to seek service from. In this dissertation, we address different types of this problem and try to analyze...
Stable transports between stationary random measures
, Article Electronic Journal of Probability ; Volume 21 , 2016 ; 10836489 (ISSN) ; Khezeli, A ; Sharif University of Technology
University of Washington
Abstract
We give an algorithm to construct a translation-invariant transport kernel between two arbitrary ergodic stationary random measures on Rd, given that they have equal intensities.As a result, this yields a construction of a shift-coupling of an arbitrary ergodic stationary random measure and its Palm version.This algorithm constructs the transport kernel in a deterministic manner given a pair of realizations of the two measures.The (non-constructive) existence of such a transport kernel was proved in [9].Our algorithm is a generalization of the work of [3], in which a construction is provided for the Lebesgue measure and an ergodic simple point process.In the general case, we limit ourselves...
Real-time trajectory generation for mobile robots
, Article 10th Congress of the Italian Association for Artificial Intelligence, AI IA 2007, Rome, 10 September 2007 through 13 September 2007 ; Volume 4733 LNAI , 2007 , Pages 459-470 ; 03029743 (ISSN); 9783540747819 (ISBN) ; Manzuri, M. T ; Razvan, M. R ; Tajfard, M ; Khoshbakht, S ; Sharif University of Technology
Springer Verlag
2007
Abstract
This paper presents a computationally effective trajectory generation algorithm for omni-directional mobile robots. This method uses the Voronoi diagram to find a sketchy path that keeps away from obstacles and then smooths this path with a novel use of Bezier curves. This method determines velocity magnitude of a robot along the curved path to meet optimality conditions and dynamic constrains using Newton method. The proposed algorithm has been implemented on real robots, and experimental results in different environments are presented. © Springer-Verlag Berlin Heidelberg 2007
Counting cells of order-k voronoi tessellations in ℝ3 with morse theory
, Article 37th International Symposium on Computational Geometry, SoCG 2021, 7 June 2021 through 11 June 2021 ; Volume 189 , 2021 ; 18688969 (ISSN) ; 9783959771849 (ISBN) ; di Montesano, S. C ; Edelsbrunner, H ; Saghafian, M ; Sharif University of Technology
Schloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing
2021
Abstract
Generalizing Lee's inductive argument for counting the cells of higher order Voronoi tessellations in ℝ2 to ℝ3, we get precise relations in terms of Morse theoretic quantities for piecewise constant functions on planar arrangements. Specifically, we prove that for a generic set of n ≥ 5 points in ℝ3, the number of regions in the order-k Voronoi tessellation is Nk−1 − (k/2)n + n, for 1 ≤ k ≤ n − 1, in which Nk−1 is the sum of Euler characteristics of these function's first k − 1 sublevel sets. We get similar expressions for the vertices, edges, and polygons of the order-k Voronoi tessellation. © Ranita Biswas, Sebastiano Cultrera di Montesano, Herbert Edelsbrunner, and Morteza Saghafian;...
Prediction of Microstructure Evolution of Severely Deformed Pure Aluminum during Annealing
, M.Sc. Thesis Sharif University of Technology ; Kazeminezhad, Mohsen (Supervisor)
Abstract
Severe Plastic Deformation (SPD) Processes have drawn lots of attention due to their ability to refine grain size and develop some properties of bulk metals and alloys. After deformation, however, ductility and formability of metals are reduced. Annealing has been used as a solution for improvement of these characteristics after deformations even after SPD processes. On the other hand, there is a possibility that during annealing grains could grow, therefore it can neutralize the effect of SPD process. Consequently, predicting behavior and evolution of microstructure during annealing finds an important role. In this research, accordingly, vertex model have been used in order to predict...
Local Homogenization of 2D Foams with Circle-Based Voronoi Structures
, M.Sc. Thesis Sharif University of Technology ; Vafai, Abolhassan (Supervisor) ; Shahbeyk, Sharif (Co-Advisor)
Abstract
The unique characteristics of solid foams make them ideal for both natural and man-made structures. The cellular structure of these materials allows for the construction of natural structures such as bone and wood that have high strength and use minimal primary materials. Their unique structure has inspired studies in the automotive and aerospace industries, leading to a new generation of lightweight materials. The focus of this study was the effects of the microstructure of foams on the macro mechanical response of specific structures. Homogenization methods are well suited for the study of these effects due to the random nature of the microstructures. One major problem in using numerical...
Parallelizing Voronoi Diagrams and Polygon Overlaying Algorithms for Multi-core Systems
,
M.Sc. Thesis
Sharif University of Technology
;
Ghodsi, Mohammad
(Supervisor)
Abstract
Todays we do not have the traditional hardware speed acceleration anymore. We have reached to the highest possible speed of single core processors. Thus, in order to run an algorithm faster we need either to improve the algorithm and make it more efficient, or to use a more powerful hardware to run it. For algorithms which we have reached to their lower bounds, we can not improve their efficiency. Furthermore, we can not have any faster traditional processor, so the only way is to use the power of parallel computation. With the advent of multicore processors the software industry has faced a new challenge, to adapt the softwares to use the power of these new processors. There are a lot of...
Sending a Gaussian source over an AWGN channel in the presence of an unknown interference
, Article 2012 46th Annual Conference on Information Sciences and Systems, CISS 2012, Princeton, NJ, 21 March 2012 through 23 March 2012 ; 2012 ; 9781467331401 (ISBN) ; Behroozi, H ; Sharif University of Technology
2012
Abstract
This paper analyzes the problem of transmitting a Gaussian source over an additive white Gaussian noise (AWGN) channel in the presence of an unknown interference. The goal is to estimate the source at the receiver with minimum mean squared error (MMSE) distortion. We introduce a lattice-based coding scheme and calculate its achievable distortion. If the interference distribution and the lattice voronoi region satisfy some conditions, the effect of interference can be reduced
A distributed algorithm for proportional task allocation in networks of mobile agents
, Article IEEE Transactions on Automatic Control ; Volume 56, Issue 2 , October , 2011 , Pages 405-410 ; 00189286 (ISSN) ; Moarref, M ; Sharif University of Technology
2011
Abstract
In a proportional task allocation problem, it is desired for robotic agents to have equal duty to capability ratios. Here, this problem is addressed as a combination of deployment and consensus problems. Tasks occur in a convex region and each task is assigned to its nearest agent. Agents are deployed on this area in order to reach consensus over the value of their duty to capability ratio. A distributed, asynchronous, and scalable algorithm is presented for solving this problem in continuous time domain
Volume degeneracy of the typical cell and the chord length distribution for Poisson-Voronoi tessellations in high dimensions
, Article Advances in Applied Probability ; Volume 40, Issue 4 , July , 2008 , Pages 919-938 ; 00018678 (ISSN) ; Sharifitabar, M ; Sharif University of Technology
2008
Abstract
This paper is devoted to the study of some asymptotic behaviors of Poisson-Voronoi tessellation in the Euclidean space as the space dimension tends to ∞. We consider a family of homogeneous Poisson-Voronoi tessellations with constant intensity λ in Euclidean spaces of dimensions n = 1, 2, 3,... First we use the Blaschke-Pètkantschin formula to prove that the variance of the volume of the typical cell tends to 0 exponentially in dimension. It is also shown that the volume of intersection of the typical cell with the co-centered ball of volume u converges in distribution to the constant λ-1 (1-e-λu). Next we consider the linear contact distribution function of the Poisson-Voronoi tessellation...
A real-time clearance-based approach for motion planning of mobile robots
, Article 7th IEEE International Conference on Cognitive Informatics, ICCI 2008, Stanford University, CA, 14 August 2008 through 16 August 2008 ; 2008 , Pages 394-401 ; 9781424425389 (ISBN) ; Iraji, R ; Manzuri Shalmani, M. T ; Sharif University of Technology
2008
Abstract
In this paper, two different important quality metrics, clearance and execution time, for motion planning of mobile robots are studied. Then a new approach, called Clearance-Based Probabilistic Roadmap Method (CBPRM (c)), is proposed which in contrast to VV(c) method, Visibility-Voronoi with clearance c, beside satisfaction of a predefined clearance is very efficient in running time. This provides the CBPRM (c) to be applicable in dynamic environments which require realtime approaches. Experiments showed that the CBPRM(c) is able to generate paths with very low execution time considering determined clearance. © 2008 IEEE
Comparing short–range and medium–range ordering in Cu–Zr and Ni–Zr metallic glasses – Correlation between structure and glass form ability
, Article Journal of Non-Crystalline Solids ; Volume 499 , 2018 , Pages 227-236 ; 00223093 (ISSN) ; Tavakoli, R ; Foroughi, A ; Sharif University of Technology
Elsevier B.V
2018
Abstract
According to recent studies, Cu–Zr and Ni–Zr binary alloying systems are very similar based on known glass-forming ability criteria, however, they exhibit significant difference in glass-forming ability in practice. In this work, local atomic structures of Cu–Zr and Ni–Zr metallic glasses are studied by molecular dynamics simulation to explain the source of mentioned difference. The total and partial distribution functions, coordination number and voronoi analysis are utilized to characterize the local atomic structures around Zr, Ni and Cu atoms. It was found that the local environment around Zr atoms is almost similar in both systems. The difference in the atomic structure in these systems...
A delaunay triangulation architecture supporting churn and user mobility in MMVEs
, Article Proceedings of the International Workshop on Network and Operating System Support for Digital Audio and Video, 3 June 2009 through 5 June 2009, Williamsburg, VA ; 2009 , Pages 61-66 ; 9781605584331 (ISBN) ; Hariri, B ; Shirmohammadi, S ; ACM SIGMM ; Sharif University of Technology
2009
Abstract
This article proposes a new distributed architecture for update message exchange inmassively multi-user virtual environments (MMVE) MMVE applications require delivery of updates among various locations in the virtual environment. The proposed architecture here exploits the location addressing of geometrical routing in order to alleviate the need for IP-specific queries. However, the use of geometrical routing requires careful choice of overlay to achieve high performance in terms of minimizing the delay. At the same time, the MMVE is dynamic, in sense that users are constantly moving in the 3D virtual space. As such, our architecture uses a distributed topology control scheme that aims at...