| |
|
Soubor publikovaných článků
DVOŘÁK, Petr
Cílem předkládaného souboru publikovaných článků je charakterizovat sociální dovednosti učitele jako součást jeho profesní kompetence a vymezit jejich význam ve výuce angličtiny komunikační metodou v edukačních interakcích ve školní třídě. Teoretickými východisky výzkumů jejichž výsledky jednotlivé články předkládají jsou funkčně komunikační přístupu k jazyku a z něj vycházející komunikační metoda. Pozornost je věnována procesům interakce, komunikace a cizojazyčnému diskurzu ve školním prostředí s akcentem na cizojazyčnou výuku dospívajících. Na základě specifik cizojazyčné edukační interakce konkretizujeme sociální dovednosti učitele a vymezujeme sociálně-dovednostní aspekty cizojazyčné edukační interakce. Zjištění výzkumů prezentovaných v předkládaných článcích se týkají zejména žákovské reflexe edukačního stylu učitelů angličtiny a edukačního působení učitele v konkrétní třídní interakci. Výzkum je rovněž zacílen na analýzu vybraných sociálně-dovednostních aspektů edukační interakce a diskurzu ve výuce angličtiny komunikační metodou. Konkrétně se jedná o žákovské a učitelské iniciace komunikace, otázky a distribuci komunikačních příležitostí.
|
|
Automata in Infinite-state Formal Verification
Lengál, Ondřej ; Jančar, Petr (oponent) ; Veith, Helmut (oponent) ; Esparza, Javier (oponent) ; Vojnar, Tomáš (vedoucí práce)
The work presented in this thesis focuses on finite state automata over finite words and finite trees, and the use of such automata in formal verification of infinite-state systems. First, we focus on extensions of a previously introduced framework for verifi cation of heap-manipulating programs-in particular programs with complex dynamic data structures-based on tree automata. We propose several extensions to the framework, such as making it fully automated or extending it to consider ordering over data values. Further, we also propose novel decision procedures for two logics that are often used in formal verification: separation logic and weak monadic second order logic of one successor. These decision procedures are based on a translation of the problem into the domain of automata and subsequent manipulation in the target domain. Finally, we have also developed new approaches for efficient manipulation with tree automata, mainly for testing language inclusion and for handling automata with large alphabets, and implemented them in a library for general use. The developed algorithms are used as the key technology to make the above mentioned techniques feasible in practice.
|
|
New Methods for Increasing Efficiency and Speed of Functional Verification
Zachariášová, Marcela ; Dohnal, Jan (oponent) ; Steininger, Andreas (oponent) ; Kotásek, Zdeněk (vedoucí práce)
In the development of current hardware systems, e.g. embedded systems or computer hardware, new ways how to increase their reliability are highly investigated. One way how to tackle the issue of reliability is to increase the efficiency and the speed of verification processes that are performed in the early phases of the design cycle. In this Ph.D. thesis, the attention is focused on the verification approach called functional verification. Several challenges and problems connected with the efficiency and the speed of functional verification are identified and reflected in the goals of the Ph.D. thesis. The first goal focuses on the reduction of the simulation runtime when verifying complex hardware systems. The reason is that the simulation of inherently parallel hardware systems is very slow in comparison to the speed of real hardware. The optimization technique is proposed that moves the verified system into the FPGA acceleration board while the rest of the verification environment runs in simulation. By this single move, the simulation overhead can be significantly reduced. The second goal deals with manually written verification environments which represent a huge bottleneck in the verification productivity. However, it is not reasonable, because almost all verification environments have the same structure as they utilize libraries of basic components from the standard verification methodologies. They are only adjusted to the system that is verified. Therefore, the second optimization technique takes the high-level specification of the system and then automatically generates a comprehensive verification environment for this system. The third goal elaborates how the completeness of the verification process can be achieved using the intelligent automation. The completeness is measured by different coverage metrics and the verification is usually ended when a satisfying level of coverage is achieved. Therefore, the third optimization technique drives generation of input stimuli in order to activate multiple coverage points in the veri\-fied system and to enhance the overall coverage rate. As the main optimization tool the genetic algorithm is used, which is adopted for the functional verification purposes and its parameters are well-tuned for this domain. It is running in the background of the verification process, it analyses the coverage and it dynamically changes constraints of the stimuli generator. Constraints are represented by the probabilities using which particular values from the input domain are selected. The fourth goal discusses the re-usability of verification stimuli for regression testing and how these stimuli can be further optimized in order to speed-up the testing. It is quite common in verification that until a satisfying level of coverage is achieved, many redundant stimuli are evaluated as they are produced by pseudo-random generators. However, when creating optimal regression suites, redundancy is not needed anymore and can be removed. At the same time, it is important to retain the same level of coverage in order to check all the key properties of the system. The fourth optimization technique is also based on the genetic algorithm, but it is not integrated into the verification process but works offline after the verification is ended. It removes the redundancy from the original suite of stimuli very fast and effectively so the resulting verification runtime of the regression suite is significantly improved.
|
|
Retargetable Analysis of Machine Code
Křoustek, Jakub ; Janoušek, Jan (oponent) ; Návrat,, Pavol (oponent) ; Kolář, Dušan (vedoucí práce)
Program analysis is a computer-science methodology whose task is to analyse the behavior of a given program. The methods of program analysis can also be used in other methodologies such as reverse engineering, re-engineering, code migration, etc. In this thesis, we focus on program analysis of a machine-code and we address the limitations of a nowadays approaches by proposing novel methods of a fast and accurate retargetable analysis (i.e. they are designed to be independent of a particular target platform). We focus on two types of analysis - dynamic analysis (i.e. run-time analysis) and static analysis (i.e. analysing application without its execution). The contribution of this thesis within the dynamic analysis lays in the extension and enhancement of existing methods and their implementation as a retargetable debugger and two types of a retargetable translated simulator. Within the static analysis, we present a concept and implementation of a retargetable decompiler that performs a program transformation from a machine code into a human-readable form of representation. All of these tools are based on several novel methods defined by the author. According to our experimental results and users feed-back, all of the proposed tools are at least fully competitive to existing solutions, while outperforming these solutions in several ways.
|
|
Packet Classification Algorithms
Puš, Viktor ; Lhotka,, Ladislav (oponent) ; Dvořák, Václav (vedoucí práce)
This thesis deals with packet classification in computer networks. Classification is the key task in many networking devices, most notably packet filters - firewalls. This thesis therefore concerns the area of computer security. The thesis is focused on high-speed networks with the bandwidth of 100 Gb/s and beyond. General-purpose processors can not be used in such cases, because their performance is not sufficient. Therefore, specialized hardware is used, mainly ASICs and FPGAs. Many packet classification algorithms designed for hardware implementation were presented, yet these approaches are not ready for very high-speed networks. This thesis addresses the design of new high-speed packet classification algorithms, targeted for the implementation in dedicated hardware. The algorithm that decomposes the problem into several easier sub-problems is proposed. The first subproblem is the longest prefix match (LPM) operation, which is used also in IP packet routing. As the LPM algorithms with sufficient speed have already been published, they can be used in out context. The following subproblem is mapping the prefixes to the rule numbers. This is where the thesis brings innovation by using a specifically constructed hash function. This hash function allows the mapping to be done in constant time and requires only one memory with narrow data bus. The algorithm throughput can be determined analytically and is independent on the number of rules or the network traffic characteristics. With the use of available parts the throughput of 266 million packets per second can be achieved. Additional three algorithms (PFCA, PCCA, MSPCCA) that follow in this thesis are designed to lower the memory requirements of the first one without compromising the speed. The second algorithm lowers the memory size by 11 % to 96 %, depending on the rule set. The disadvantage of low stability is removed by the third algorithm, which reduces the memory requirements by 31 % to 84 %, compared to the first one. The fourth algorithm combines the third one with the older approach and thanks to the use of several techniques lowers the memory requirements by 73 % to 99 %.
|
|
Network-wide Security Analysis
de Silva, Hidda Marakkala Gayan Ruchika ; Šafařík,, Jiří (oponent) ; Šlapal, Josef (oponent) ; Švéda, Miroslav (vedoucí práce)
The objective of the research is to model and analyze the effects of dynamic routing protocols. The thesis addresses the analysis of service reachability, configurations, routing and security filters on dynamic networks in the event of device or link failures. The research contains two main sections, namely, modeling and analysis. First section consists of modeling of network topology, protocol behaviors, device configurations and filters. In the modeling, graph algorithms, routing redistribution theory, relational algebra and temporal logics were used. For the analysis of reachability, a modified topology table was introduced. This is a unique centralized table for a given network and invariant for network states. For the analysis of configurations, a constraint-based analysis was developed by using XSD Prolog. Routing and redistribution were analyzed by using routing information bases and for analyzing the filtering rules, a SAT-based decision procedure was incorporated. A part of the analysis was integrated to a simulation tool at OMNeT++ environment. There are several innovations introduced in this thesis. Filtering network graph, modified topology table, general state to reduce the state space, modeling devices as filtering nodes and constraint-based analysis are the key innovations. Abstract network graph, forwarding device model and redistribution with routing information are extensions of the existing research. Finally, it can be concluded that this thesis discusses novel approaches, modeling methods and analysis techniques in the area of dynamic networks. Integration of these methods into a simulation tool will be a very demanding product for the network designers and the administrators.
|
|
Evolutionary Approach to Synthesis and Optimization of Ordinary and Polymorphic Circuits
Gajda, Zbyšek ; Schmidt, Jan (oponent) ; Zelinka,, Ivan (oponent) ; Sekanina, Lukáš (vedoucí práce)
This thesis deals with the evolutionary design and optimization of ordinary and polymorphic circuits. New extensions of Cartesian Genetic Programming (CGP) that allow reducing of the computational time and obtaining more compact circuits are proposed and evaluated. Second part of the thesis is focused on new methods for synthesis of polymorphic circuits. Proposed methods, based on polymorphic binary decision diagrams and polymorphic multiplexing, extend the ordinary circuit representations with the aim of including polymorphic gates. In order to reduce the number of gates in circuits synthesized using proposed methods, an evolutionary optimization based on CGP is implemented and evaluated. The implementations of polymorphic circuits optimized by CGP represent the best known solutions if the number of gates is considered as the target criterion.
|
|
Stability and convergence of numerical computations
Sehnalová, Pavla ; Dalík, Josef (oponent) ; Horová, Ivana (oponent) ; Kunovský, Jiří (vedoucí práce)
The aim of this thesis is to analyze the stability and convergence of fundamental numerical methods for solving ordinary differential equations. These include one-step methods such as the classical Euler method, Runge-Kutta methods and the less well known but fast and accurate Taylor series method. We also consider the generalization to multistep methods such as Adams methods and their implementation as predictor-corrector pairs. Furthermore we consider the generalization to multiderivative methods such as Obreshkov method. There is always a choice in predictor-corrector pairs of the so-called mode of the method and in this thesis both PEC and PECE modes are considered. The main goal and the new contribution of the thesis is the use of a special fourth order method consisting of a two-step predictor followed by an one-step corrector, each using second derivative formulae. The mathematical background of historical developments of Nordsieck representation, the algorithm of choosing a variable stepsize or an error estimation are discussed. The current approach adapts well to the multiderivative situation in variable stepsize formulations. Experiments for linear and non-linear problems and the comparison with classical methods are presented.
|
|
Extensions to Probabilistic Linear Discriminant Analysis for Speaker Recognition
Plchot, Oldřich ; Fousek, Petr (oponent) ; McCree,, Alan (oponent) ; Burget, Lukáš (vedoucí práce)
This thesis deals with probabilistic models for automatic speaker verification. In particular, the Probabilistic Linear Discriminant Analysis (PLDA) model, which models i--vector representation of speech utterances, is analyzed in detail. The thesis proposes extensions to the standard state-of-the-art PLDA model. The newly proposed Full Posterior Distribution PLDA models the uncertainty associated with the i--vector generation process. A new discriminative approach to training the speaker verification system based on the~PLDA model is also proposed. When comparing the original PLDA with the model extended by considering the i--vector uncertainty, results obtained with the extended model show up to 20% relative improvement on tests with short segments of speech. As the test segments get longer (more than one minute), the performance gain of the extended model is lower, but it is never worse than the baseline. Training data are, however, usually available in the form of segments which are sufficiently long and therefore, in such cases, there is no gain from using the extended model for training. Instead, the training can be performed with the original PLDA model and the extended model can be used if the task is to test on the short segments. The discriminative classifier is based on classifying pairs of i--vectors into two classes representing target and non-target trials. The functional form for obtaining the score for every i--vector pair is derived from the PLDA model and training is based on the logistic regression minimizing the cross-entropy error function between the correct labeling of all trials and the probabilistic labeling proposed by the system. The results obtained with discriminatively trained system are similar to those obtained with generative baseline, but the discriminative approach shows the ability to output better calibrated scores. This property leads to a better actual verification performance on an unseen evaluation set, which is an important feature for real use scenarios.
|
host ::
