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Transport and Localization in Classical and Quantum Billiards
Črt Lozej, 2020, doktorska disertacija

Opis: In this thesis the classical and quantum dynamics in billiard systems are considered. Extensive numerical studies of the classical transport properties in several examples of billiard families including the ergodic Bunimovich stadium and cut-circle billiards and the mixed-type Robnik and lemon billiards are performed. The analysis of the transport is based on the random model of diffusion which assumes that due the strongly chaotic dynamics the motion of the orbit on the discretized phase space is temporally uncorrelated. The cause of the deviations from the random model dynamics is traced to dynamical trapping due to stickiness. A novel approach to locally quantifying stickiness based on the statistics of the recurrence times is presented and applied to distinguish between exponential decays of recurrence times and other types of decays. This enables the identification of sticky areas in the chaotic components. Detailed maps of their structure for a wide range of parameter values, mapping the evolution of the mixed-phase spaces and revealing some particularly interesting special examples are presented. The recurrence time distributions in sticky areas are found to be well described by a mixture of exponential decays. The transport of particle ensembles in the momentum space of classical billiards is described by using an inhomogeneous diffusion model and the classical transport times are determined. The classical transport times are vital for the analysis of the localization of chaotic eigenstates in quantum billiards. The control parameter that describes the the degree of localization of the chaotic quantum eigenstates is the ratio between the Heisenberg time (Planck's constant divided by the mean level spacing) and the classical transport time. Extensive numerical calculations of the high-lying spectra and eigenstates of the stadium, Robnik and lemon quantum billiards are performed. The spectral statistics are analysed in terms of the standard methods of quantum chaos. The level repulsion exponent of localized eigenstates is found to be a rational function of the control parameter. The degree of localization is determined with respect to localization measures based on the Poincaré-Husimi representation of the eigenstates. The mean localization measure is found to be a rational function of the control parameter and linearly related to the level repulsion exponent. The distributions of the localization measures are analysed and found to be of a universal shape well described by a two parameter empirical distribution in billiards with no apparent stickiness. The nonuniversal system specific features of localization measure distributions are related to the presence of sticky areas in the phase spaces of classical billiards with specific examples shown.
Ključne besede: Transport, localization, chaos, quantum chaos, Hamiltonian systems, level spacing distribution, mixed phase space, billiard, quantum billiard, Husimi functions, stickiness, cantorus, chaotic eigenstates, level repulsion.
Objavljeno: 13.01.2021; Ogledov: 274; Prenosov: 46
.pdf Celotno besedilo (24,93 MB)

Prometno-tehničko projektiranje "shared space" prostora primjenom metoda konflikata
Patricia Blažić, 2020, magistrsko delo

Opis: Osnovni uvjet za pravilno prometno-tehničko projektiranje Shared space prostora je pravilna primjena urbanih i infrastrukturnih elemenata i zadovoljavanje parametara za tehničko projektiranje prostora kao rezultat sigurnosne analize primjenom metode konflikata. Ovim magistarskim radom obuhvatit će se sigurnosna analiza primjenom metode konflikata u svrhu pravilnog prometno – tehničkog projektiranja. Sigurnosna analiza sastojat će se od analize specifičnih konflikata korisnika Shared space-a i ozbiljnosti njihovih međusobnih sukoba. Ozbiljnost sukoba ponajviše ovisi o kretanju i ponašanju korisnika. Navedenom analizom ustvrdit će se konfliktne površine i konfliktne točke. Na temelju rezultata određuje se pravilni odabir projektno – tehničkih elemenata u svrhu smanjenja konfliktnih površina i smanjenju ozbiljnosti sukoba. Kroz praktični dio primijenit će se prometno sigurnosna analiza primjenom metode konflikata, analiza kretanja i ponašanja korisnika te analiza ozbiljnosti sukoba. Praktični primjer ovog magistarskog rada bit će rekonstrukcija Vojašniške ulice u Shared space prostor. Karakteristika Vojašniške ulice je neposredna blizina trga i ugostiteljskih sadržaja s jedne strane te šetnica s druge strane. Atraktivnost prostora privlači mnogobrojne posjetitelje različite životne dobi te njihove potrebe. Upravo ta različitost potreba dovodi do učestalih prijelaza pješaka i biciklista na nepredviđenim prijelazima. Navedeno čini predmetnu lokaciju mjestom za opravdanu primjenu Shared space prostora.
Ključne besede: Shared space, metoda konflikata, projektiranje, parametri, oprema
Objavljeno: 14.07.2020; Ogledov: 212; Prenosov: 29
.pdf Celotno besedilo (34,68 MB)

Nonlinear control of a one-dimensional self-balancing system with an inertia wheel
Marko Boršić, 2019, magistrsko delo

Opis: The master’s thesis describes the development of a one-dimensional self-balancing system with an inertia wheel. The plan was to establish all the theoretical knowledge that was gathered throughout the process of studying at the University and to finish the practical model which has the ability to balance in one dimension. The paper contains a description of constructing the mechanical part of the pendulum, developed in SolidWorks software. It also contains the execution of the mathematical model of the inverted pendulum. The simulation was conducted in Matlab/Simulink software. Based on the results of the simulation, the design of the controller for the EC motor was made. Designed controllers and measured data required for the active balance of the system were implemented on the microcontroller STM32F4. To measure the angle and angle velocity, the gyroscope and accelerometer on the MPU6050 sensor were used. The results of the simulation and of the practical model are presented in this paper.
Ključne besede: modeling, inertia wheel, backstepping, state space, sliding mode
Objavljeno: 29.03.2019; Ogledov: 1087; Prenosov: 207
.pdf Celotno besedilo (3,00 MB)

Green's function for tangentialy loaded horizontaly layered half-space
Tomaž Pliberšek, Andrej Umek, 2008, izvirni znanstveni članek

Opis: The topic of this paper is a novel evaluation of the integral representation of the surface Greenćs function for a layered half-space, loaded on its surface by a harmonic tangential point force. The equations of motions are reduced to wave equations by the introduction of wave potentials. The Hankel transform is applied to them and they are consecutively solved leading to the integral representation of surface displacements. They are consecutively evaluated by the proposed three step procedure. First the singularity is extracted. It is further noted that so obtained integrals, after suitably chosen branch cuts and analytic continuation of integrands are introduced, can be evaluated by contour integration for an arbitrary number of layers. They are, therefore, expressed by number of residues at the poles of integrand and the integrals along finite portions of the branch cuts. The latter ones can easily be evaluated to any desired accuracy leading to a closed form solution. Some numerical results corroborating the presented approach are given.
Ključne besede: elastodynamics, elastic wave propagation, Green`s function, horizontaly layered half-space, horizontal point load
Objavljeno: 05.06.2018; Ogledov: 476; Prenosov: 56
.pdf Celotno besedilo (329,66 KB)
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Shopping and business centres in Sarajevo
Rahman Nurković, 2012, izvirni znanstveni članek

Opis: In the paper, influence of shopping and business centres: Mercator, Tuš, Obi Robot, Konzum and BBI on development of Sarajevo city is analysed. Results of the survey made among visitors indicate to presence of social functions (walk, leisure, recreation, fun, socialization) in five centres. The mentioned functions are more expressed in new shopping centres, while shopping is the most important motive of visits to commercial centres. Sarajevo city makes, with its surrounding, a functionally connected wholeness – city, respectively an urban region.
Ključne besede: shopping and business centres, central business centre, public space, social functions, Sarajevo
Objavljeno: 10.04.2018; Ogledov: 481; Prenosov: 61
.pdf Celotno besedilo (233,01 KB)
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Restraints and opportunities of the Romanian rural areas
Vasile Surd, 2010, pregledni znanstveni članek

Opis: Although Romania disposes of an extremely valuable agricultural land, it has proved to be insufficient and irrationally exploited in the last two decades, as a direct consequence of the programme for returning the agricultural areas to the former individual landowners. The lack of technological agricultural means for cultivating the land, its excessive allotment, as well as the rather inappropriate involvement of the political factor in the decision making process and the invasion of imported agricultural products have generated a continuous process of degradation of the rural life as a whole and certain repercussions on the food safety. Currently, more than 50% of the Romanian agricultural area is not being cultivated, while the state imports more than 70% of alimentary products every year.
Ključne besede: urban-rural space, rural state, rural policy infrastructure, agricultural land, Romania
Objavljeno: 29.03.2018; Ogledov: 396; Prenosov: 44
.pdf Celotno besedilo (181,12 KB)
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Development of rural space in post-communist southeast Europe after 1989
Peter Jordan, 2009, pregledni znanstveni članek

Opis: This paper investigates the reasons for the current state of rural space in Southeast Europe, as well as its current structure. It is confirmed that pre-Communist structures, as well as divergent Communist systems and policies, contributed as much to current structures as have divergent post-Communist approaches and developments. Thus, we meet today very different situations in the rural space of Yugoslavian successor states on the one hand, and of other post-Communist countries of Southeast Europe with a planned economy (Romania, Bulgaria and Albania) on the other. But even the countries of former Yugoslavia show many divergences, mainly due to divergent demographic development in the wake of the Yugoslavian dissolution wars.
Ključne besede: structure of rural space, communist systems, transformation, agricultural policies, Southeast Europe
Objavljeno: 19.03.2018; Ogledov: 430; Prenosov: 80
.pdf Celotno besedilo (226,19 KB)
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Parameter space for a dissipative Fermi-Ulam model
Diego F. M. Oliveira, Edson D. Leonel, 2011, izvirni znanstveni članek

Opis: The parameter space for a dissipative bouncing ball model under the effect of inelastic collisions is studied. The system is described using a two-dimensional nonlinear area-contracting map. The introduction of dissipation destroys the mixed structure of phase space of the non-dissipative case, leading to the existence of a chaotic attractor and attracting fixed points, which may coexist for certain ranges of control parameters. We have computed the average velocity for the parameter space and made a connection with the parameter space based on the maximum Lyapunov exponent. For both cases, we found an infinite family of self-similar structures of shrimp shape, which correspond to the periodic attractors embedded in a large region that corresponds to the chaotic motion.
Ključne besede: parameter space, Fermi-Ulam model, inelastic collision
Objavljeno: 03.07.2017; Ogledov: 997; Prenosov: 305
.pdf Celotno besedilo (2,84 MB)
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AdS(2) holographic dictionary
Mirjam Cvetič, Ioannis Papadimitriou, 2016, izvirni znanstveni članek

Opis: We construct the holographic dictionary for both running and constant dilaton solutions of the two dimensional Einstein-Maxwell-Dilaton theory that is obtained by a circle reduction from Einstein-Hilbert gravity with negative cosmological constant in three dimensions. This specific model ensures that the dual theory has a well de fined ultraviolet completion in terms of a two dimensional conformal field theory, but our results apply qualitatively to a wider class of two dimensional dilaton gravity theories. For each type of solutions we perform holographic renormalization, compute the exact renormalized one-point functions in the presence of arbitrary sources, and derive the asymptotic symmetries and the corresponding conserved charges. In both cases we find that the scalar operator dual to the dilaton plays a crucial role in the description of the dynamics. Its source gives rise to a matter conformal anomaly for the running dilaton solutions, while its expectation value is the only non trivial observable for constant dilaton solutions. The role of this operator has been largely overlooked in the literature. We further show that the only non trivial conserved charges for running dilaton solutions are the mass and the electric charge, while for constant dilaton solutions only the electric charge is non zero. However, by uplifting the solutions to three dimensions we show that constant dilaton solutions can support non trivial extended symmetry algebras, including the one found by Comp ere, Song and Strominger [1], in agreement with the results of Castro and Song [2]. Finally, we demonstrate that any solution of this specific dilaton gravity model can be uplifted to a family of asymptotically AdS(2) x S-2 or conformally AdS(2) x S-2 solutions of the STU model in four dimensions, including non extremal black holes. The four dimensional solutions obtained by uplifting the running dilaton solutions coincide with the so called 'subtracted geometries', while those obtained from the uplift of the constant dilaton ones are new.
Ključne besede: 2D gravity, AdS-CFT correspondence, black holes, space-time symmetries
Objavljeno: 27.06.2017; Ogledov: 666; Prenosov: 300
.pdf Celotno besedilo (1,01 MB)
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A benchmark of lidar-based single tree detection methods using heterogeneous forest data from the alpine space
Lothar Eysn, Markus Hollaus, Eva Lindberg, Frédéric Berger, Jean-Matthieu Monnet, Michele Dalponte, Milan Kobal, Marco Antonio Pellegrini, Emanuele Lingua, Domen Mongus, Norbert Pfeifer, 2015, izvirni znanstveni članek

Opis: In this study, eight airborne laser scanning (ALS)-based single tree detection methods are benchmarked and investigated. The methods were applied to a unique dataset originating from different regions of the Alpine Space covering different study areas, forest types, and structures. This is the first benchmark ever performed for different forests within the Alps. The evaluation of the detection results was carried out in a reproducible way by automatically matching them to precise in situ forest inventory data using a restricted nearest neighbor detection approach. Quantitative statistical parameters such as percentages of correctly matched trees and omission and commission errors are presented. The proposed automated matching procedure presented herein shows an overall accuracy of 97%. Method based analysis, investigations per forest type, and an overall benchmark performance are presented. The best matching rate was obtained for single-layered coniferous forests. Dominated trees were challenging for all methods. The overall performance shows a matching rate of 47%, which is comparable to results of other benchmarks performed in the past. The study provides new insight regarding the potential and limits of tree detection with ALS and underlines some key aspects regarding the choice of method when performing single tree detection for the various forest types encountered in alpine regions.
Ključne besede: single tree extraction, airborne laser scanning, forest inventory, comparative testing, co-registration, mountain forests, Alpine space, matching
Objavljeno: 21.06.2017; Ogledov: 468; Prenosov: 294
.pdf Celotno besedilo (13,97 MB)
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