Showing papers by "Brno University of Technology published in 2004"

Abstract Regular Model Checking

Abstract: We propose abstract regular model checking as a new generic technique for verification of parametric and infinite-state systems. The technique combines the two approaches of regular model checking and verification by abstraction. We propose a general framework of the method as well as several concrete ways of abstracting automata or transducers, which we use for modelling systems and encoding sets of their configurations as usual in regular model checking. The abstraction is based on collapsing states of automata (or transducers) and its precision is being incrementally adjusted by analysing spurious counterexamples. We illustrate the technique on verification of a wide range of systems including a novel application of automata-based techniques to an example of systems with dynamic linked data structures.

Development of high sensitivity ethanol gas sensors based on Pt-doped SnO2 surfaces

Abstract: This paper describes how thick-film technology was used to fabricate small, robust, sensitive, and selective semiconductor metal oxide (SMO) sensors to detect traces of ethanol vapours in air. The sensing parameters of several active layers were studied including: sensitivity, response repeatability, stability and selectivity. The response to different species of five differently doped SnO2 sensors and a commercially available one were measured at concentrations between 1 ppb and 1000 ppm. Interaction was extremely high when ethanol came into contact with the Pt-doped SnO2 surface. The change in resistance of the Pt-doped sensors was between 2 and 55 times higher than the change in the commercial one. The Pt-doped SnO2 material is less resistant, more sensitive and shows faster response to ethanol than pure SnO2. Since the detection limit for ethanol is at sub-ppb level, the fabricated sensors could be used for alcoholmeters or for on-line monitoring and controlling the concentration of ethanol in fruit ripening storage chambers.

Towards Lower Error Rates in Phoneme Recognition

Abstract: We investigate techniques for acoustic modeling in automatic recognition of context-independent phoneme strings from the TIMIT database. The baseline phoneme recognizer is based on TempoRAl Patterns (TRAP). This recognizer is simplified to shorten processing times and reduce computational requirements. More states per phoneme and bi-gram language models are incorporated into the system and evaluated. The question of insufficient amount of training data is discussed and the system is improved. All modifications lead to a faster system with about 23.6% relative improvement over the baseline in phoneme error rate.

MIXED INTEGER-DISCRETE-CONTINUOUS OPTIMIZATION BY DIFFERENTIAL EVOLUTION Part 1: the optimization method

Abstract: This article discusses solving non-linear programming problems containing integer, discrete and continuous variables. The Part 1 of the article describes a novel optimization method based on Differential Evolution algorithm. The required handling techniques for integer, discrete and continuous variables are described including the techniques needed to handle boundary constraints as well as those needed to simultaneously deal with several non-linear and non-trivial constraint functions. In Part 2 of the article a mechanical engineering design related numerical example, design of a coil spring, is given to illustrate the capabilities and the practical use of the method. It is demonstrated that the described approach is capable of obtaining high quality solutions. The novel method is relatively easy to implement and use, effective, efficient and robust, which makes it as an attractive and widely applicable approach for solving practical engineering design problems.

Calculations of theoretical strength: State of the art and history

Abstract: Current state and historical evolution of theoretical strength calculations is presented as a brief overview completed by a database of selected theoretical and experimental results. Principles of a sophisticated analysis of mechanical stability of crystals are elucidated by means of a schematic example. Stability conditions and Jacobian matrixes are presented for selected crystalline symmetries and deformation paths. The importance of this analysis for understanding micromechanics of fracture is shown against the background of the influence of crystal defects. Differences between theoretical and experimental theoretical strength (TS) values are discussed and some challenging tasks are outlined for the near future.

The role of ab initio electronic structure calculations in studies of the strength of materials

Abstract: In this paper we give an account of applications of quantum-mechanical (first-principles) electronic structure calculations to the problem of theoretical tensile strength in metals and intermetallics. First, we review previous as well as ongoing research on this subject. We then describe briefly the electronic structure calculational methods and simulation of the tensile test. This approach is then illustrated by calculations of theoretical tensile strength in iron and in the intermetallic compound Ni 3 Al. The anisotropy of calculated tensile strength is explained in terms of higher-symmetry structures encountered along the deformation paths studied. The table summarizing values of theoretical tensile strengths calculated up to now is presented and the role of ab initio electronic structure calculations in contemporary studies of the strength of material is discussed.

Regular Model Checking Using Inference of Regular Languages.

Abstract: Regular model checking is a method for verifying infinite-state systems based on coding their configurations as words over a finite alphabet, sets of configurations as finite automata, and transitions as finite transducers. We introduce a new general approach to regular model checking based on inference of regular languages. The method builds upon the observation that for infinite-state systems whose behaviour can be modelled using length-preserving transducers, there is a finite computation for obtaining all reachable configurations up to a certain length n. These configurations are a (positive) sample of the reachable configurations of the given system, whereas all other words up to length n are a negative sample. Then, methods of inference of regular languages can be used to generalize the sample to the full reachability set (or an overapproximation of it). We have implemented our method in a prototype tool which shows that our approach is competitive on a number of concrete examples. Furthermore, in contrast to all other existing regular model checking methods, termination is guaranteed in general for all systems with regular sets of reachable configurations. The method can be applied in a similar way to dealing with reachability relations instead of reachability sets too.

Pt-loaded Al2O3 catalytic filters for screen-printed WO3 sensors highly selective to benzene

Abstract: We describe the fabrication of low-cost benzene sensors by using screen-printing technology. Two different types of catalytic filters were developed to enhance the sensitivity of tungsten oxide films to benzene. The first type of filter consists of a porous Al 2 O 3 layer, loaded with a Pt layer on its surface. The second type of filter is based on a porous Al 2 O 3 layer, with Pt homogeneously distributed in its bulk. These filters were used to coat WO 3 -based sensors. The presence of by-products resulting from the incomplete catalytic combustion of benzene in the catalytic filters (that could further interact with the WO 3 film), explains the higher sensitivity of the coated sensors, as compared with the sensitivity of bare tungsten oxide sensors. In particular, it is shown that a very selective benzene sensor can be obtained by combining a coated and uncoated tungsten oxide sensor. This combined sensor, selectively detects benzene in a wide concentration range in the presence of interfering species such as ethanol, ammonia, nitrogen dioxide and water vapour.

Ab initio calculations of ideal tensile strength and mechanical stability in copper

Abstract: A simulation of a tensile test of copper crystal along the [001] direction is performed using the Vienna ab initio simulation package (VASP). Stability conditions for a uniaxially loaded system are presented and analysed and the ideal (theoretical) tensile strength for the loading along the [001] direction is determined to be 9.4 GPa in tension and 3.5 GPa in compression. A comparison with experimental values is performed.

Superresolution of ultrasound images using the first and second harmonic signal

Abstract: This paper presents a new method of blind two-dimensional (2-D) homomorphic deconvolution and speckle reduction applied to medical ultrasound images. The deconvolution technique is based on an improved 2-D phase unwrapping scheme for pulse estimation. The input images are decomposed into minimum-phase and allpass components. The 2-D phase unwrapping is applied only to the allpass component. The 2-D phase of the minimum-phase component is derived by a Hilbert transform. The accuracy of 2-D phase unwrapping is also improved by processing small (16/spl times/16 pixels) overlapping subimages separately. This takes the spatial variance of the ultrasound pulse into account. The deconvolution algorithm is applied separately to the first and second harmonic images, producing much sharper images of approximately the same resolution and different speckle patterns. Speckle reduction is made by adding the envelope images of the deconvolved first and second harmonic images. Neither the spatial resolution nor the frame rate decreases, as the common compounding speckle reduction techniques do. The method is tested on sequences of clinical ultrasound images, resulting in high-resolution ultrasound images with reduced speckle noise.

A route toward more selective and less humidity sensitive screen-printed SnO2 and WO3 gas sensitive layers

Abstract: We have studied the effect of adhesion promoters (bismuth and copper oxides) on the gas sensing properties of screen-printed tin and tungsten oxide sensors. The gas-sensitive pastes were prepared by mixing either tin or tungsten oxide powders with an organic vehicle based on therpineol. Two different additives to enhance the adhesion of the active films to the substrate (Bi 2 O 3 or Bi 2 O 3 +Cu 2 O) were included in the paste composition. The films that resulted after printing and firing have high porosity and excellent adherence. Morphology studies have shown that the films have well-defined microstructure and gas sensitivity studies have shown that additives, not only help in promoting film adhesion, but also modify the response of the sensors. Their sensitivity at different operating temperatures was evaluated for ammonia, nitrogen dioxide, ethanol, benzene, carbon monoxide, methane and water vapour. It was found that WO 3 sensors containing Bi 2 O 3 and Cu 2 O were always more sensitive to ammonia and, that WO 3 sensors containing Bi 2 O 3 only were more sensitive to nitrogen dioxide when operated at 250 °C. The reaction paths that explain the sensitivity changes observed by the inclusion of Cu 2 O in tungsten oxide sensors are introduced and discussed.

Thermoanalytical investigation of lignite humic acids fractions

Abstract: Differential scanning calorimetry (DSC) and thermogravimetry (TG) studies of humic acids (HA) sequentially extracted at pH 7, 8, 9 and 10 by phosphate and pyrophosphate buffers have been carried out. Supplement information were provided by elementary analysis and FTIR spectroscopy to characterize and evaluate in details the thermooxidative behavior of HA fractions. The exothermic DSC profiles of the HA samples extracted by phosphate buffers or by pyrophosphates were shifted to lower temperatures in comparison with the original sample and showed narrow distribution of humic molecules. Experimental data showed dependency of HA fraction composition on the pH used during extraction. DSC experimental data showed 1 endothermic and from 2-5 exothermic peaks associated with mass loss recorded by TG measurement. Higher degree of aliphaticity observed on samples extracted at lower pH did not remarkably affect the DSC peak temperature of the first decomposition step associated with aliphatic moieties and functional groups decomposition and recombination reactions. On the other hand, such dependency was observed in higher temperature range where destruction of aromatic structures took part. The behavior of HA samples (even after separation of specific fractions) showed high complexity of system, which resulted in complicated physical and chemical processes occurred during thermooxidation. Observed stability and released heat were affected by many factors, among them evaporation of volatile part of humic matter and a slight contribution of weak interactions among humic molecules were considered.

Influence of the doping method on the sensitivity of Pt-doped screen-printed SnO2 sensors

Abstract: In this work, we study the influence of the introduction method of Pt atoms on the sensitivity to traces of ethanol of Pt-doped SnO2 sensors. The tin oxide films were obtained by a screen-printing process. Two different methods were employed to introduce Pt atoms on SnO2 films. In the first one, the Pt atoms were added to the screen-printed tin oxide layer by using RF magnetron sputtering and a subsequent thermal treatment. The second method consisted of mixing SnO2 and Pt pastes before the screen-printing process. The different active layers (including un-doped tin oxide) were carefully examined relative to their sensitivity to ethanol at different working temperatures. Sensors prepared by the second method showed sensitivity to ethanol four times higher than one of the sensors prepared by the first method and 12 times higher than un-doped sensors. XPS and scanning electron microscopy (SEM) measurements showed that this behaviour could be associated with the spatial distribution of the doping elements within the tin oxide film. While in Pt-sputtered sensors most of the Pt atoms were found at the surface of the active layer, for the sensors made by mixing Pt and SnO2 pastes, a homogeneous distribution of the Pt atoms was observed. These sensors show high sensitivity and fast response time to ethanol vapours, with a detection limit in the ppb range.

Fabrication of zirconia- and ceria-based thin-wall tubes by thermoplastic extrusion

Abstract: Thin-wall tubes made of zirconia stabilized by 8 mol% of yttria and of ceria doped by 10 mol% of gadolinia were prepared by thermoplastic extrusion. The rheological behaviour of the ceramic mixtures prepared and the effect of rheological properties on the deformation of tubes were studied. After sintering, the diameter of tubes was 10.5 mm and their wall thickness ranged from 270 to 420 μm. The deformation and shape irregularity of sintered tubes were determined. The tubes, which were sintered at a temperature of 1500 °C, had a relative density of more than 98% t.d. Flexural strength and fracture toughness of sintered ceramics were determined on test bars prepared by injection moulding from thermoplastic mixtures identical to those used for extrusion. The fracture toughness established was 1.7 MPa m 0.5 for yttria-stabilized zirconia, and 1.1 MPa m 0.5 for gadolinia-doped ceria.

The Voltage Conveyor May Have in Fact Found its Way into Circuit Theory

Abstract: Summary This paper deals with the counterpart to the well-known current conveyor. The n -port voltage conveyor is defined. Terminology, schematic Symbols of voltage conveyors and their adjoint zero-class elements are presented. The design procedures of an analog filter and a sinusoidal oscillator employing voltage conveyors are shown.

Characterization of acoustic and electromagnetic emission sources

Abstract: The creation of cracks is accompanied by electric charge redistribution due to loosened chemical bonds. Electric charges on crack walls create dipole moments. Vibrations of crack walls produce time-dependent dipole moments and, consequently, electric and magnetic fields are generated. An electric signal is induced on metal electrodes. Information about the vibration of crack walls was obtained from this signal analysis. For crack lengths below 1 mm the electrical signal has a frequency of over 2 MHz. In this paper the frequency analysis was performed in a frequency band of up to 5 MHz.

Estimator Comparison of the Nakagami-m Parameter and its Application in Echocardiography

Abstract: This article deals with the comparison of various estimators of the m parameter from the Nakagami distribution. This kind of distribution has been used in many engineering applications and we present another possible application in biomedical engineering, particularly the ultrasound tissue characterization in the echocardiographic application. Matlab 6.5 was used as a proper tool for fast and efficient scientific research. ( ) ( ) 0 e 2 2 1 2 ≥ Ω Γ =         Ω − − V V m m V p mV

An Evolvable Combinational Unit for FPGAs

Abstract: A complete hardware implementation of an evolvable combinational unit for FPGAs is presented. The proposed combinational unit consisting of a virtual reconfigurable circuit and evolutionary algorithm was described in VHDL independently of a target platform, i.e. as a soft IP core, and realized in the COMBO6 card. In many cases the unit is able to evolve (i.e. to design) the required function automatically and autonomously, in a few seconds, only on the basis of interactions with an environment. A number of circuits were successfully evolved directly in the FPGA, in particular, 3-bit multipliers, adders, multiplexers and parity encoders. The evolvable unit was also tested in a simulated dynamic environment and used to design various circuits specified by randomly generated truth tables.

The study of H2O2 generation by DC diaphragm discharge in liquids

Abstract: The contribution gives results of hydrogen peroxide generation obtained in the DC diaphragm discharge in water solutions. Chemical active species, such as hydroxyl radicals and hydrogen peroxide are produced by the discharge. The dependencies of hydrogen peroxide concentration on high, voltage (magnitude and polarity), material of electrodes and dielectric diaphragm are studied for one electrolyte (NaCl) used for initial solution conductivity. The used dielectric diaphragms differ in material and they have various thickness.

On routine implementation of virtual evolvable devices using COMBO6

Abstract: This paper introduces an approach showing that a complete implementation of a digital evolvable hardware system can automatically be created from a high-level specification. The approach generates the implementation of a virtual reconfigurable circuit and evolutionary algorithm independently of a target platform, i.e. as a soft IP core. The method is evaluated on the development of two high-performance evolvable systems that are utilized for fast evolutionary design of small combinational circuits, such as 3 - 3-bit multipliers. The COMBO6 card is employed for these experiments.

Statistical model of free-space optical data link

Abstract: The paper deals with a statistical model of free-space optical (FSO) data link that takes into account the duration of individual fade events. It is well known that a general data transmission using the Internet protocol (IP) is almost insensitive to link interruptions for hundreds of milliseconds while real-time video services will be badly affected. The statistical model is based on the knowledge of the probability density function of random attenuations and the probability density function of durations of the fades. The paper shows the results from our test site obtained from 1999 to 2001.

Determination of carbohydrates in juices by capillary electrophoresis, high-performance liquid chromatography, and matrix-assisted laser desorption/ionization-time of flight-mass spectrometry.

Abstract: The objective of this work was to develop a sample preparation procedure for determination of the carbohydrate profiles in commercial juice samples by three principally different analytical methods: capillary electrophoresis (CE) with indirect detection, high-performance liquid chromatography (HPLC), and matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS). The preparation and purification of juice samples prior to analysis is described. The method using Carrez reagents was found to be an efficient preparation tool for all three methods. The addition of Carrez reagents to the samples for mass analysis improved the quality of the mass spectra of oligosaccharides. The amounts of glucose, fructose, and sucrose as major carbohydrates in fruit juices measured by CE using a simple instrument are in good agreement with the HPLC values and the data declared by the producers of the juices. The results from both methods are critically evaluated and their impact for studies of authenticity is discussed. The decrease of sucrose amount during the storage of samples was explained by acid hydrolysis of this disaccharide.

Quantification of the effect of specimen geometry on the fatigue crack growth response by two-parameter fracture mechanics

Abstract: Discrepancies in fatigue crack growth rate and threshold values observed in different specimen geometries are analyzed and discussed. To explain the discrepancies, a phenomenological approach is suggested going out from the assumption of linear elastic fracture mechanics. To this aim, two-parameter constraint-based fracture mechanics is used and the different levels of constraint in the vicinity of the fatigue crack tip are characterized by means of the T-stress. The results of the theoretical analyses correspond to the presented experimental data. It is concluded that under small scale yielding conditions (corresponding to high cycle loading) low level of the constraint (corresponding to negative values of the T-stress) substantially increases the rate of the fatigue crack propagation. The results presented make it possible to relate the experimentally measured data obtained on the specimens with different geometries and thereby contribute to more reliable estimates of the residual fatigue life of structures.

Measurement and analysis of dynamic and acoustic parameters of rail fastening

Abstract: A new method using time and frequency related transformations has been developed for the evaluation of response signals obtained by rail fastening analysis In the paper the laboratory measurements and dynamic and acoustic parameter analyses of flexible fastening of Vossloh SKL14 type have been described The method can also be used for designing new rail fastening systems and their parts

Registration of bimodal retinal images - improving modifications

Abstract: The proper optical disc segmentation in images provided by confocal laser scanning ophthalmoscope and by color fundus-camera is a necessary step in early glaucoma or arteriosclerosis detection. Fusing information from both modalities into a vector-valued image is expected to improve the segmentation reliability. The paper describes a registration of these images using optimization based on mutual information criterion function extended with gradient-image mutual information. The controlled random search (CRS) has been found to be a more robust optimization routine than the simulated annealing (SA) while tested on a set of 174 image pairs. Finally, the multi-resolution algorithm for bimodal retinal image registration achieving the success-rate of 94% is proposed.

Face tracking in meeting room scenarios using omnidirectional views

Abstract: The robust localization and tracking of faces in video streams is a fundamental concern for many subsequent multi-modal recognition approaches. Especially in meeting scenarios several independent processing queues often exist that use the position and gaze of faces, such as group action- and face recognizers. The costs for multiple camera recordings of meeting scenarios are obviously higher compared to those of a single omnidirectional camera setup. Therefore it would be desirable to use these easier to acquire omnidirectional recordings. The present work presents art implementation of a robust particle filter based face-tracker using omnidirectional views. It is shown how omnidirectional images have to be unwarped before they can be processed by localization and tracking systems being invented for undistorted material. The performance of the system is evaluated on a part of the PETS-ICVS 2003 smart meeting room dataset.