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Search Results: 1 - 10 of 543351 matches for " Gábor Vásárhelyi "
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Identification of Behaviour in Freely Moving Dogs (Canis familiaris) Using Inertial Sensors
Linda Gerencsér, Gábor Vásárhelyi, Máté Nagy, Tamas Vicsek, Adam Miklósi
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0077814
Abstract: Monitoring and describing the physical movements and body postures of animals is one of the most fundamental tasks of ethology. The more precise the observations are the more sophisticated the interpretations can be about the biology of a certain individual or species. Animal-borne data loggers have recently contributed much to the collection of motion-data from individuals, however, the problem of translating these measurements to distinct behavioural categories to create an ethogram is not overcome yet. The objective of the present study was to develop a “behaviour tracker”: a system composed of a multiple sensor data-logger device (with a tri-axial accelerometer and a tri-axial gyroscope) and a supervised learning algorithm as means of automated identification of the behaviour of freely moving dogs. We collected parallel sensor measurements and video recordings of each of our subjects (Belgian Malinois, N=12; Labrador Retrievers, N=12) that were guided through a predetermined series of standard activities. Seven behavioural categories (lay, sit, stand, walk, trot, gallop, canter) were pre-defined and each video recording was tagged accordingly. Evaluation of the measurements was performed by support vector machine (SVM) classification. During the analysis we used different combinations of independent measurements for training and validation (belonging to the same or different individuals or using different training data size) to determine the robustness of the application. We reached an overall accuracy of above 90% perfect identification of all the defined seven categories of behaviour when both training and validation data belonged to the same individual, and over 80% perfect recognition rate using a generalized training data set of multiple subjects. Our results indicate that the present method provides a good model for an easily applicable, fast, automatic behaviour classification system that can be trained with arbitrary motion patterns and potentially be applied to a wide range of species and situations.
Patterns, transitions and the role of leaders in the collective dynamics of a simple robotic flock
Norbert Tarcai,Csaba Virágh,Dániel ábel,Máté Nagy,Péter L. Várkonyi,Gábor Vásárhelyi,Tamás Vicsek
Physics , 2012, DOI: 10.1088/1742-5468/2011/04/P04010
Abstract: We have developed an experimental setup of very simple self-propelled robots to observe collective motion emerging as a result of inelastic collisions only. A circular pool and commercial RC boats were the basis of our first setup, where we demonstrated that jamming, clustering, disordered and ordered motion are all present in such a simple experiment and showed that the noise level has a fundamental role in the generation of collective dynamics. Critical noise ranges and the transition characteristics between the different collective patterns were also examined. In our second experiment we used a real-time tracking system and a few steerable model boats to introduce intelligent leaders into the flock. We demonstrated that even a very small portion of guiding members can determine group direction and enhance ordering through inelastic collisions. We also showed that noise can facilitate and speed up ordering with leaders. Our work was extended with an agent-based simulation model, too, and high similarity between real and simulation results were observed. The simulation results show clear statistical evidence of three states and negative correlation between density and ordered motion due to the onset of jamming. Our experiments confirm the different theoretical studies and simulation results in the literature about collision-based, noise-dependent and leader-driven self-propelled particle systems.
Flocking algorithm for autonomous flying robots
Csaba Virágh,Gábor Vásárhelyi,Norbert Tarcai,Tamás Sz?rényi,Gerg? Somorjai,Tamás Nepusz,Tamás Vicsek
Physics , 2013, DOI: 10.1088/1748-3182/9/2/025012
Abstract: Animal swarms displaying a variety of typical flocking patterns would not exist without underlying safe, optimal and stable dynamics of the individuals. The emergence of these universal patterns can be efficiently reconstructed with agent-based models. If we want to reproduce these patterns with artificial systems, such as autonomous aerial robots, agent-based models can also be used in the control algorithm of the robots. However, finding the proper algorithms and thus understanding the essential characteristics of the emergent collective behaviour of robots requires the thorough and realistic modeling of the robot and the environment as well. In this paper, first, we present an abstract mathematical model of an autonomous flying robot. The model takes into account several realistic features, such as time delay and locality of the communication, inaccuracy of the on-board sensors and inertial effects. We present two decentralized control algorithms. One is based on a simple self-propelled flocking model of animal collective motion, the other is a collective target tracking algorithm. Both algorithms contain a viscous friction-like term, which aligns the velocities of neighbouring agents parallel to each other. We show that this term can be essential for reducing the inherent instabilities of such a noisy and delayed realistic system. We discuss simulation results about the stability of the control algorithms, and perform real experiments to show the applicability of the algorithms on a group of autonomous quadcopters.
Outdoor flocking and formation flight with autonomous aerial robots
Gábor Vásárhelyi,Csaba Virágh,Gerg? Somorjai,Norbert Tarcai,Tamás Sz?rényi,Tamás Nepusz,Tamás Vicsek
Computer Science , 2014,
Abstract: We present the first decentralized multi-copter flock that performs stable autonomous outdoor flight with up to 10 flying agents. By decentralized and autonomous we mean that all members navigate themselves based on the dynamic information received from other robots in the vicinity. We do not use central data processing or control; instead, all the necessary computations are carried out by miniature on-board computers. The only global information the system exploits is from GPS receivers, while the units use wireless modules to share this positional information with other flock members locally. Collective behavior is based on a decentralized control framework with bio-inspiration from statistical physical modelling of animal swarms. In addition, the model is optimized for stable group flight even in a noisy, windy, delayed and error-prone environment. Using this framework we successfully implemented several fundamental collective flight tasks with up to 10 units: i) we achieved self-propelled flocking in a bounded area with self-organized object avoidance capabilities and ii) performed collective target tracking with stable formation flights (grid, rotating ring, straight line). With realistic numerical simulations we demonstrated that the local broadcast-type communication and the decentralized autonomous control method allows for the scalability of the model for much larger flocks.
Sensitivity analysis of GSI based mechanical characterization of rock mass
P. Ván,B. Vásárhelyi
Physics , 2012,
Abstract: Recently, the rock mechanical and rock engineering designs and calculations are frequently based on Geological Strength Index (GSI) method, because it is the only system that provides a complete set of mechanical properties for design purpose. Both the failure criteria and the deformation moduli of the rock mass can be calculated with GSI based equations, which consists of the disturbance factor, as well. The aim of this paper is the sensitivity analysis of GSI and disturbance factor dependent equations that characterize the mechanical properties of rock masses. The survey of the GSI system is not our purpose. The results show that the rock mass strength calculated by the Hoek-Brown failure criteria and both the Hoek-Diederichs and modified Hoek-Diederichs deformation moduli are highly sensitive to changes of both the GSI and the D factor, hence their exact determination is important for the rock engineering design.
The BiSearch web server
Tamás Arányi, András Váradi, István Simon, Gábor E Tusnády
BMC Bioinformatics , 2006, DOI: 10.1186/1471-2105-7-431
Abstract: The web tool is composed of a primer-design and an electronic PCR (ePCR) algorithm. The completely reformulated ePCR module detects potential mispriming sites as well as undesired PCR products on both cDNA and native or bisulfite-treated genomic DNA libraries. Due to the new algorithm of the current version, the ePCR module became approximately hundred times faster than the previous one and gave the best performance when compared to other web based tools. This high-speed ePCR analysis made possible the development of the new option of high-throughput primer screening. BiSearch web server can be used for academic researchers at the http://bisearch.enzim.hu webcite site.BiSearch web server is a useful tool for primer-design for any DNA template and especially for bisulfite-treated genomes. The ePCR tool for fast detection of mispriming sites and alternative PCR products in cDNA libraries and native or bisulfite-treated genomes are the unique features of the new version of BiSearch software.Polymerase chain reaction (PCR) is a widely used technique both in clinical diagnosis and research applications. The success of a PCR reaction is essentially determined by the oligonucleotides used as primers for the amplification of the target sequence. Although a large variety of primer-design softwares exist, some aspects of the design are rarely considered by these programs. For example only very few programs can design primers to amplify bisulfite treated DNA [1,2]. This is surprising since the number of studies including PCR on bisulfite treated DNA templates is exponentially growing. Bisulfite treated DNA is used to determine CpG methylation profile [3,4]. Methylation of the mammalian DNA influences gene expression regulation, cell division and chromosome stability [5]. Aberrant DNA methylation profiles are generally observed in pathological processes, such as cancerogenesis [6]. Bisulfite genomic PCR based diagnostic tools were developed to detect these aberrant methylation
A simple combinatorial proof of Shapiro's Catalan convolution
Gábor V. Nagy
Mathematics , 2012, DOI: 10.1016/j.aam.2012.07.002
Abstract: Shapiro proved an elegant convolution formula involving Catalan numbers of even index. This paper gives a simple combinatorial proof of his formula. In addition, we show that it is equivalent with the alternating convolution formula of central binomial coefficients.
On Induced Subgraphs of Finite Graphs not Containing Large Empty and Complete Subgraphs
Gábor Sági
Mathematics , 2012,
Abstract: In their celebrated paper [Ramsey-Type Theorems, Discrete Appl. Math. 25 (1989) 37-52], Erd\H{o}s and Hajnal asked the following: is it true, that for any finite graph H there exists a constant c(H) such that for any finite graph G, if G does not contain complete or empty induced subgraphs of size at least |V(G)|^c(H), then H can be isomorphically embedded into G ? The positive answer has become known as the Erd\H{o}s-Hajnal conjecture. In Theorem 3.13 of the present paper we settle this conjecture in the affirmative. To do so, we are studying here the fine structure of ultraproducts of finite sets, so our investigations have a model theoretic character.
A generalization of the Erd?s-Ko-Rado Theorem
Gábor Hegedüs
Mathematics , 2015,
Abstract: Our main result is a new upper bound for the size of k-uniform, L-intersecting families of sets, where L contains only positive integers. We characterize extremal families in this setting. Our proof is based on the Ray-Chaudhuri--Wilson Theorem. As an application, we give a new proof for the Erd\H{o}s-Ko-Rado Theorem, improve Fisher's inequality in the uniform case and give an uniform version of the Frankl-F\"uredi conjecture .
A Bollobás-type theorem for affine subspaces
Gábor Hegedüs
Mathematics , 2015,
Abstract: Let $W$ denote the $n$-dimensional affine space over the finite field $\mathbb F_q$. We prove here a Bollob\'as-type upper bound in the case of the set of affine subspaces. We give a construction of a pair of families of affine subspaces, which shows that our result is almost sharp.
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