11. Optimized PID position control of a nonlinear system based on correlating the velocity with position errorNenad Muškinja, Matej Rižnar, 2015, izvirni znanstveni članek Opis: We examined a design approach for a PID controller for a nonlinear ball and beam system. Main objective of our research was to establish a nonmodel-based control system, which would also not be dependent on a specific ball and beam hardware setup. The proposed PID controller setup is based on a cascaded configuration of an inner PID ball velocity control loop and an outer proportional ball position control loop. The effectiveness of the proposed controller setup was first presented in simulation environment in comparison to a hardware dependent PD cascaded controller, along with a more comprehensive study on possible design approach for optimal PID controller parameters in relation to main functionality of the controller setup. Experimental real-time control results were then obtained on a laboratory setup of the ball and beam system on which PD cascaded controller could not be applied without parallel system model processing.
Ključne besede: position control, nonlinear system, position error
Objavljeno v DKUM: 15.06.2017; Ogledov: 1171; Prenosov: 450
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12. Reduction of the mean hedging transaction costsMiklavž Mastinšek, 2015, izvirni znanstveni članek Opis: Transaction costs of derivative hedging appear in financial markets. This paper considers the problem of delta hedging and the reduction of expected proportional transaction costs. In the literature the expected approximate proportional transaction costs are customarily estimated by the gamma term, usually the largest term of the associated series expansion. However, when options are to expire in a month or few weeks, other terms may become even larger so that more precise estimates are needed. In this paper, different higher-order estimates of proportional transaction costs are analyzed. The problem of the reduction of expected transaction costs is considered. As a result, a suitably adjusted delta is given, for which the expected approximate proportional transaction costs can be reduced. The order of the mean and the variance of the hedging error can be preserved. Several examples are provided.
Ključne besede: derivatives, delta hedging, transaction costs, hedging error
Objavljeno v DKUM: 03.04.2017; Ogledov: 1276; Prenosov: 197
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13. ERROR PROBABILITY MODEL FOR IEEE 802.15.4 WIRELESS TRANSMISSION WITH CO-CHANNEL INTERFERENCE AND BACKGROUND NOISEUroš Pešović, 2016, doktorska disertacija Opis: Data transmission sent through wireless channel is usually affected by background noise, multipath fading and interference which cause data errors. Influence of such disturbances is the most commonly expressed in a form of error probability statistics. Effects of these disturbances on IEEE 802.15.4 wireless transmissions are previously studied, except influence of co-channel interference (CCI) which originates from collision between IEEE 802.15.4 devices which perform simultaneous radio transmission. Our thesis puts forward the assumption that it is possible to derive more accurate analytical error probability model for higher data level error probability parameters without the idealization of PN spreading sequences. Additionally, thesis is that is possible to derive an accurate analytical error probability model in the case of CCI influenced by background noise by consideration of constellation diagram. IEEE 802.15.4 standard uses CSMA/CA (Carrier Sense Multiple Access with Collision Detection) channel access mechanism to prevent collisions between devices, but this mechanism doesn't provide protection from hidden node problem which is primary source of co-channel interference. Using Monte Carlo simulations we determined frequency of hidden node collisions, which shown that co-channel interference frequently occur in parts of the network with high traffic load. Some prior works in this field tend to idealize these non-ideal spreading sequences in order to simplify calculations for error probability parameters. Our doctor thesis presents analytical model of data level error probability parameters (symbol, bit and packet) for IEEE 802.15.4, which uses original non-ideal spreading sequences without their idealization. Proposed error probability model consists of mutually dependent chip, symbol, bit and packet error probability models. Derived error probability models are linked together, so each of error probability parameters can be determined using error probability parameter from the previous stage. Error probability model for IEEE 802.15.4 wireless communication could be used in network simulation tools in order to accurately simulate energy efficient medium access protocols in realistic scenarios. Presented theoretical results are tested by independent numerical simulation of IEEE 802.15.4 transmission according to Monte Carlo method. Simulation results shows that derived models for error probability parameters were matched by two simulation scenarios in background noise, for multipath fading and co-channel interface, respectively Furthermore, the accuracy of derived mathematical models was tested in real-world experiment using IEEE 802.15.4 compliant wireless transceivers for creating co-channel interference. Packets were received by software defined radio platform, which enabled realization of coherent receiver in which all error probability statistics could be collected. The results of the experiment show consistency with proposed analytical error probability models, but some deviations are caused by poor preamble synchronization under low SNR (Signal to Noise Ratio) value. The thesis was proved with Monte Carlo simulations of the physical level of the IEEE 802.15.4 communication and experimental measurements on a real physical communication system.
Ključne besede: IEEE 802.15.4 standard, error probability model, co-channel interference, Rician fading channel, additive white Gaussian noise, wireless transmission, wireless sensor networks, numerical simulations, software defined radio
Objavljeno v DKUM: 14.10.2016; Ogledov: 2502; Prenosov: 149
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14. Foreign students' speech in EnglandManca Potušek, 2016, diplomsko delo Opis: The diploma thesis focuses on the influence of the French, Italian and Spanish language on the Standard Southern British English pronunciation. The research is based on the recordings of 10 French, 9 Italian and 9 Spanish students who spent half a year in England as Erasmus exchange students.
The theoretical part starts with an introductory chapter describing a short history of all four languages, as well as the position of the English language in the world and in the European Union. East Midlands English and Standard Southern British English are then presented with their phonological characteristics. Furthermore, the vowel systems of French, Italian and Spanish language are presented together with the most common errors the speakers of these languages encounter when pronouncing English vowels. In the following chapter the term “interlanguage” and research methods as Contrastive Analysis and Error Analysis are described. In the last segment of the theoretical part we are dealing with so-called formants which are frequencies that the vowels are made of and are essential for identification of a vowel.
In the empirical part, Error Analysis is used as a research method. The key part of the research is the analysis of the recordings of foreign students’ pronunciation of 11 SSBE vowels. The results of the research clearly prove a strong influence of the French, Italian, and Spanish accents on the pronunciation of SSBE vowels, as well as a great impact of General American. To analyse the data, the descriptive method was used.
The findings of the dissertation could be of help to other researchers or English teachers should they find themselves teaching in France, Italy or Spain.
Ključne besede: Standard Southern British English, vowels, formants, foreign students, Error Analysis
Objavljeno v DKUM: 08.09.2016; Ogledov: 1601; Prenosov: 92
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15. Perfect codes in direct products of cycles - a complete characterizationJanez Žerovnik, 2008, izvirni znanstveni članek Opis: Let ▫$G = times^n_{i=1}C_{ell_i}$▫ be a direct product of cycles. It is known that for any ▫$r le 1$▫, and any ▫$n le 2▫$, each connected component of ▫$G$▫ contains a so-called canonical ▫$r$▫-perfect code provided that each ▫$ell_i$▫ is a multiple of ▫$r^n + (r+1)^n$▫. Here we prove that up to a reasonably defined equivalence, these are the only perfect codes that exist.
Ključne besede: matematika, teorija grafov, korekcijske kode, direktni produkt grafov, popolne kode, cikli, mathematics, graph theory, error-correcting codes, direct product of graphs, perfect codes, cycles
Objavljeno v DKUM: 10.07.2015; Ogledov: 1886; Prenosov: 94
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16. An almost complete description of perfect codes in direct products of cyclesSandi Klavžar, Simon Špacapan, Janez Žerovnik, 2006, izvirni znanstveni članek Opis: Let ▫$G = times_{i=1}^nC_{ell_i}$▫ be a direct product of cycles. It is proved that for any ▫$r ge 1$▫, and any ▫$n ge 2$▫, each connected component of ▫$G$▫ contains an ▫$r$▫-perfect code provided that each ▫$ell_i$▫ is a multiple of ▫$r^n + (r+1)^n▫$. On the other hand, if a code of ▫$G$▫ contains a given vertex and its canonical local vertices, then any ▫$ell_i$▫ is a multiple of ▫$r^n + (r+1)^n$▫. It is also proved that an ▫$r$▫-perfect code ▫$(r ge 2)$▫ of ▫$G$▫ is uniquely determined by ▫$n$▫ vertices, and it is conjectured that for ▫$r ge 2$▫ no other codes in ▫$G$▫ exist other than the constructed ones.
Ključne besede: mathematics, graph theory, error-correcting codes, direct product of graphs, perfect codes, cycles
Objavljeno v DKUM: 10.07.2015; Ogledov: 24186; Prenosov: 104
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