Showing papers by "Brno University of Technology published in 2007"

Probabilistic and Bottle-Neck Features for LVCSR of Meetings

Abstract: In recent years, probabilistic features became an integral part of state-of-the-are LVCSR systems. In this work, we are exploring the possibility of obtaining the features directly from neural net without the necessity of converting output probabilities to features suitable for subsequent GMM-HMM system. We experimented with 5-layer MLP with bottle-neck in the middle layer. After training such a neural net, we used outputs of the bottle-neck as features for GMM-HMM recognition system. The benefits are twofold: first, improvement was gained when these features are used instead of the probabilistic features, second, the size of the system was reduced, as only part of the neural net is used. The experiments were performed on meetings recognition task defined in MST RT'05 evaluation.

Analysis of Feature Extraction and Channel Compensation in a GMM Speaker Recognition System

Abstract: In this paper, several feature extraction and channel compensation techniques found in state-of-the-art speaker verification systems are analyzed and discussed. For the NIST SRE 2006 submission, cepstral mean subtraction, feature warping, RelAtive SpecTrAl (RASTA) filtering, heteroscedastic linear discriminant analysis (HLDA), feature mapping, and eigenchannel adaptation were incrementally added to minimize the system's error rate. This paper deals with eigenchannel adaptation in more detail and includes its theoretical background and implementation issues. The key part of the paper is, however, the post-evaluation analysis, undermining a common myth that ldquothe more boxes in the scheme, the better the system.rdquo All results are presented on NIST Speaker Recognition Evaluation (SRE) 2005 and 2006 data.

Interfacial water at hydrophobic and hydrophilic surfaces: depletion versus adsorption.

Abstract: The structure of the water-solid interface for widely varying surface properties is investigated with Monte Carlo simulations using the SPC/E water model. Of particular interest is the relation between the wetting coefficient as a measure of the hydrophobicity of the substrate and the density depletion close to the solid surface. The substrates are modeled as rigid ordered lattices of sites that interact with water molecules through an orientation-independent Lennard-Jones potential of varying strength. Hydrophilic character is obtained by addition of polar hydroxyl groups on the substrate surface, and the influence of density, spatial distribution, and angular orientation of the polar groups on the interfacial water structure is studied.

The AMI System for the Transcription of Speech in Meetings

Abstract: This paper describes the AMI transcription system for speech in meetings developed in collaboration by five research groups. The system includes generic techniques such as discriminative and speaker adaptive training, vocal tract length normalisation, heteroscedastic linear discriminant analysis, maximum likelihood linear regression, and phone posterior based features, as well as techniques specifically designed for meeting data. These include segmentation and cross-talk suppression, beam-forming, domain adaptation, Web-data collection, and channel adaptive training. The system was improved by more than 20% relative in word error rate compared to our previous system and was used in the NIST RT106 evaluations where it was found to yield competitive performance.

Comparison of two different solvents employed for pressurised fluid extraction of stevioside from Stevia rebaudiana: methanol versus water.

Abstract: Pressurised fluid extraction using water or metha- nol was employed for the extraction of stevioside from Stevia rebaudiana Bertoni. The extraction method was optimised in terms of temperature and duration of the static or the dynamic step. Extracts were analysed by liquid chromatography followed by UV and mass-spectrometric (MS) detections. Thermal degradation of stevioside was the same in both solvents within the range 70-160 °C. Methanol showed better extraction ability for isolation of stevioside from Stevia rebaudiana leaves than water within the range 110-160 °C. However, water represents the green alternative to methanol. The limit of detection of stevioside in the extract analysed was 30 ng for UV detection and 2 ng for MS detection.

Asymptotic Prediction of Energetic-Statistical Size Effect from Deterministic Finite-Element Solutions

Abstract: An improved form of a recently derived energetic-statistical formula for size effect on the strength of quasibrittle structures failing at crack initiation is presented and exploited to perform stochastic structural analysis without the burden of stochastic nonlinear finite-element simulations. The characteristic length for the statistical term in this formula is deduced by considering the limiting case of the energetic part of size effect for a vanishing thickness of the boundary layer of cracking. A simple elastic analysis of stress field provides the large-size asymptotic deterministic strength, and also allows evaluating the Weibull probability integral which yields the mean strength according to the purely statistical Weibull theory. A deterministic plastic limit analysis of an elastic body with a through- crack imagined to be filled by a perfectly plastic "glue" is used to obtain the small-size asymptote of size effect. Deterministic nonlinear fracture simulations of several scaled structures with commercial code ATENA based on the crack band model suffice to calibrate the deterministic part of size effect. On this basis, one can calibrate the energetic-statistical size effect formula, giving the mean strength for any size of geometrically scaled structures. Stochastic two-dimensional nonlinear simulations of the failure of Malpasset Dam demonstrate good agreement with the calibrated formula and the need to consider in dam design both the deterministic and statistical aspects of size effect. The mean tolerable displacement of the abutment of this arch dam is shown to have been approximately one half of the value indicated by the classical deterministic local analysis based on material strength.

Thermodynamic assessment of the Bi–Sn–Zn System

Abstract: A thermodynamic assessment of the Bi‐Sn‐Zn ternary system was carried out using the CALPHAD approach along with thermodynamic descriptions from new assessments of the Bi‐Sn and Bi‐Zn systems. Selected experimental data from the literature and our own work were also used. New sets of optimized thermodynamic parameters were obtained that lead to a very good fit between the calculated and experimental data. The Bi‐Sn‐Zn system is one of the candidates for lead-free solder materials. c 2007 Elsevier Ltd. All rights reserved.

Magnetodielectric effect and optic soft mode behaviour in quantum paraelectric EuTiO3 ceramics

Abstract: Infrared reflectivity and time-domain terahertz transmission spectra of EuTiO3 ceramics revealed a polar optic phonon at 6–300 K whose softening is fully responsible for the recently observed quantum paraelectric behaviour. Even if our EuTiO3 ceramics show lower permittivity than the single crystal due to a reduced density and/or small amount of secondary pyrochlore Eu2Ti2O7 phase, we confirmed a magnetic field dependence of the permittivity, also slightly smaller than in single crystal. An attempt to reveal the soft phonon dependence at 1.8 K on the magnetic field up to 13 T remained below the accuracy of our infrared reflectivity experiment.

Compaction and Pressureless Sintering of Zirconia Nanoparticles

Abstract: Four nanometer-sized zirconia powders stabilized by 3 mol% Y 2 O 3 were used for the preparation of dense bulk ceramics. Ceramic green bodies were prepared by cold isostatic pressing at pressures of 300-1000 MPa. The size of the pores in ceramic green bodies and their evolution during sintering were correlated with the characteristics of individual nanopowders and with the sintering behavior of powder compacts. Only homogeneous green bodies with pores of 99% t.d.) at a sufficiently low temperature to keep the grain sizes in the range < 100 nm. Powders with uniform particles 10 nm in size yielded green bodies of required microstructure. These nanoparticle compacts were sintered without pressure to give bodies (diameter 20 mm, thickness 4 mm) with a relative density higher than 99% and a grain size of about 85 nm (as determined by the linear intercept method).

Real-time Terrain Deformations

Abstract: This paper presents a method for a physically based real-time terrain deformation. The motivation originates from the fact that there exist many deformable models, but the terrain deformation is a special problem in the field of computer graphics. OpenSceneGraph toolkit provides an excellent environment for the large terrain visualization and it was accepted as a standard for many graphic specialists. Therefore, the main goal of this method is the local deformation ability of some large terrain, which is represented by a sub-graph of OpenSceneGraph scene. However, the technique may be easily adaptable to any terrain representation. The results show a great potential of the used method and thus there is outlined the future work at the end.

fMRI evaluation of hemispheric language dominance using various methods of laterality index calculation.

Abstract: Several functional MR imaging studies evaluating the lateralisation of linguistic functions in patients who underwent Wada testing have been reported. There is extensive variance in the Laterality index (LI) calculation across the studies, and the optimal calculation method remains unclear. We attempted to calculate the LI in different ways in the same subjects, in order to find the LI calculation method with the highest correlation to the Wada test. Fifteen patients (10 females, 5 males) suffering from medically intractable temporal lobe epilepsy (TLE) (12 left, 3 right) were admitted for the study. The patients underwent a standardized bilateral intracarotid short-acting barbiturate test. Language testing included spontaneous speech, oral comprehension, reading, object and picture naming, and repetition. All the tasks were scored separately in order to increase the possibility of correlation between Wada and LI. A silent phonemic verbal fluency task (VFT) was used as a language paradigm for functional measurement. Regions of interest (ROIs), with a known association with language function (Broca’s area, the lateral prefrontal cortex, etc.), were defined. First, the LIs were calculated from the ROIs using a previously reported method (simple suprathreshold count). Next, we used several new methods of LI calculation (t–weighting of voxels, methods independent of the choice of the statistical threshold, etc.) The most significant correlation with Wada was proven in the LIs that were evaluated from Broca’s area (up to R = 0.94, P = 1 × 10−7). However, the new LI calculation methods used in the present study did not produce a statistically significant benefit in comparison to previously reported methods.

Monitoring of the heavy-metal hyperaccumulation in vegetal tissues by X-ray radiography and by femto-second laser induced breakdown spectroscopy.

Abstract: This article reports on the utilization of X-ray microradiography and laser induced breakdown spectroscopy (LIBS) techniques for investigation of the metal accumulation in different part of leaf samples. The potential of the LIBS-analysis for finding the proper plant species for phytoremediation is compared with the results of microradiography measurements at the HERCULES source at ENEA, Rome (Italy) and X-ray microradiography experiments at the ELETTRA Synchrotron, Trieste (Italy).

The solar eclipse of 2006 and the origin of raylike features in the white-light corona

Abstract: Solar eclipse observations have long suggested that the white-light corona is permeated by long fine rays. By comparing photographs of the 2006 March 29 total eclipse with current-free extrapolations of photospheric field measurements and with images from the Solar and Heliospheric Observatory (SOHO), we deduce that the bulk of these linear features fall into three categories: (1) polar and low-latitude plumes that overlie small magnetic bipoles inside coronal holes, (2) helmet streamer rays that overlie large loop arcades and separate coronal holes of opposite polarity, and (3) pseudostreamer rays that overlie twin loop arcades and separate coronal holes of the same polarity. The helmet streamer rays extend outward to form the plasma sheet component of the slow solar wind, while the plumes and pseudostreamers contribute to the fast solar wind. In all three cases, the rays are formed by magnetic reconnection between closed coronal loops and adjacent open field lines. Although seemingly ubiquitous when seen projected against the sky plane, the rays are in fact rooted inside or along the boundaries of coronal holes.

The experimental study of the Bi-Sn, Bi-Zn and Bi-Sn-Zn systems

Abstract: The binary Bi‐Sn was studied by means of SEM (Scanning Electron Microscopy)/EDS (Energy-Dispersive solid state Spectrometry), DTA (Differential Thermal Analysis)/DSC (Differential Scanning Calorimetry) and RT-XRD (Room Temperature X-Ray Diffraction) in order to clarify discrepancies concerning the Bi reported solubility in (Sn). It was found that (Sn) dissolves approximately 10 wt% of Bi at the eutectic temperature. The experimental effort for the Bi‐Zn system was limited to the investigation of the discrepancies concerning the solubility limit of Zn in (Bi) and the solubility of Bi in (Zn). Results indicate that the solubility of both elements in the respective solid solution is approximately 0.3 wt% at 200 C. Three different features were studied within the Bi‐Sn‐Zn system. Although there are enough data to establish the liquid miscibility gap occurring in the phase diagram of binary Bi‐Zn, no data could be found for the ternary. Samples belonging to the isopleths with w(Bi) 10% and w(Sn) 5%, 13% and 19% were measured by DTA/DSC. The aim was to characterize the miscibility gap in the liquid phase. Samples belonging to the isopleths with w(Sn) 40%, 58%, 77/81% and w(Zn) 12% were also measured by DTA/DSC to complement the study of Bi‐Sn‐Zn. Solubilities in the solid terminal solutions were determined by SEM/EDS. Samples were also analyzed by RT-XRD and HT-XRD (High Temperature X-Ray Diffraction) confirming the DTA/DSC results for solid state phase equilibria. c 2007 Elsevier Ltd. All rights reserved.

Healing data races on-the-fly

Abstract: Testing of concurrent software is extremely difficult. Despite all the progress in the testing and verification technology, concurrent bugs, the most common of which are deadlocks and races, make it to the field. This paper describes a set of techniques, implemented in a tool called ConTest, allowing concurrent programs to self-heal at run-time. Concurrent bugs have the very desirable property for healing that some of the interleaving produce correct results while in others bugs manifest. Healing concurrency problems is about limiting, or changing the probability of interleaving, such that bugs will be seen less. When healing concurrent programs, if a deadlock does not result from limiting the interleaving, we are sure that the result of the healed program could have been in the original program and therefore no new functional bug has been introduced. In this initial work which deals with different types of data races, we suggest three types of healing mechanisms: (1) changing the probability of interleaving by introducing sleep or yield statements or by changing thread priorities, (2) removing interleaving using synchronisation commands like locking and unlocking certain mutexes or waits and notifies, and (3) removing the result of "bad interleaving" by replacing the value of variables by the one that "should" have been taken. We also classify races according to the relevant healing strategies to apply.

Comparison of GC–MS and LC–MS methods for the analysis of antioxidant phenolic acids in herbs

Abstract: Two methods were developed for the quantitative analysis of phenolic acids in herb extracts. The methods were based on liquid chromatography-time-of-flight mass spectrometry (LC-TOFMS) and gas chromatography-mass spectrometry (GC-MS). The methods were compared in terms of their linearity, repeatability, selectivity, sensitivity and the speed of the analysis. The sensitivity was good for both methods, with limits of detection of <80 ng/ml for most of the compounds. The relative standard deviations (RSD) of the peak areas were on average 7.2% for the LC-TOFMS method and 1.4% for the GC-MS method. Both methods were found to be suitable for the determination of the target analytes, although GC-MS was better suited to the quantitative determination of compounds present at low concentrations.

Energetic–statistical size effect simulated by SFEM with stratified sampling and crack band model

Abstract: The paper presents a model that extends the stochastic finite element method to the modelling of transitional energetic–statistical size effect in unnotched quasibrittle structures of positive geometry (i.e. failing at the start of macro-crack growth), and to the low probability tail of structural strength distribution, important for safe design. For small structures, the model captures the energetic (deterministic) part of size effect and, for large structures, it converges to Weibull statistical size effect required by the weakest-link model of extreme value statistics. Prediction of the tail of extremely low probability such as one in a million, which needs to be known for safe design, is made feasible by the fact that the form of the cumulative distribution function (cdf) of a quasibrittle structure of any size has been established analytically in previous work. Thus, it is not necessary to turn to sophisticated methods such as importance sampling and it suffices to calibrate only the mean and variance of this cdf. Two kinds of stratified sampling of strength in a finite element code are studied. One is the Latin hypercube sampling of the strength of each element considered as an independent random variable, and the other is the Latin square design in which the strength of each element is sampled from one overall cdf of random material strength. The former is found to give a closer estimate of variance, while the latter gives a cdf with smaller scatter and a better mean for the same number of simulations. For large structures, the number of simulations required to obtain the mean size effect is greatly reduced by adopting the previously proposed method of random property blocks. Each block is assumed to have a homogeneous random material strength, the mean and variance of which are scaled down according to the block size using the weakest-link model for a finite number of links. To check whether the theoretical cdf is followed at least up to tail beginning at the failure probability of about 0.01, a hybrid of stratified sampling and Monte Carlo simulations in the lowest probability stratum is used. With the present method, the probability distribution of strength of quasibrittle structures of positive geometry can be easily estimated for any structure size. Copyright © 2007 John Wiley & Sons, Ltd.

An evolvable hardware system in Xilinx Virtex II Pro FPGA

Abstract: In this paper, a new circuit architecture for image filter evolution is proposed. The evolvable system is based on the implementation of a search algorithm in the PowerPC processor which is available in Xilinx Virtex II Pro Field Programmable Gate Arrays (FPGAs). Candidate filters are evaluated in a domain-specific virtual reconfigurable circuit implemented using a reconfigurable logic of the same FPGA. As the PowerPC processor enables to execute more sophisticated search algorithms than an original solely circuit-based solution by Martinek and Sekanina, a higher performance can be obtained. In the FPGA, a resulting human-competitive filter can be evolved in 15 sec in average.

Utilizing of Square Wave Voltammetry to Detect Flavonoids in the Presence of Human Urine.

Abstract: About biological affecting of flavonoids on animal organisms is known less,thus we selected flavonoids, flavanones and flavones, and their glycosides, which wereexamined as potential inducers of cytochrome(s) P450 when administrated by gavages intoexperimental male rats. The study was focused on induction of CYP1A1, the majorcytochrome P450 involved in carcinogen activation. The data obtained demonstrate thenecessity of taking into account not only ability of flavonoids to bind to Ah receptor(induction factor) but also to concentrate on their distribution and metabolism (includingcolon microflora) in the body. After that we examined certain flavonoids as potential inducers of cytochrome P450, we wanted to suggest and optimize suitable electrochemical technique for determination of selected flavonoids (quercetin, quercitrin, rutin, chrysin and diosmin) in body liquids. For these purposes, we selected square wave voltannetry using carbon paste electrode. Primarily we aimed on investigation of their basic electrochemical behaviour. After that we have optimized frequency, step potential and supporting electrolyte. Based on the results obtained, we selected the most suitable conditions for determination of the flavonoids as follows: frequency 180 Hz, step potential 1.95 mV/s and phosphate buffer of pH 7 as supporting electrolyte. Detection limits (3 S/N) of the flavonoids were from units to tens of nM except diosmin, where the limit were higher than μM. In addition, we attempted to suggest a sensor for analysis of flavonoids in urine. It clearly follows from the results obtained that flavonoids can be analysed in the presence of animal urine, because urine did not influence much the signals of flavonoids (recoveries of the signals were about 90 %).

Roadmap methods vs. cell decomposition in robot motion planning

Abstract: The task of planning trajectories plays an important role in transportation, robotics, information systems (sending messages), etc. In robot motion planning, the robot should pass around obstacles from a given starting position to a given target position, touching none of them, i.e. the goal is to find a collision-free path from the starting to the target position. Research on path planning has yielded many fundamentally different approaches to the solution of this problem that can be classified as roadmap methods (visibility graph method, Voronoi diagram) and methods based on cell decomposition. Assuming movements only in a restricted number of directions (eight directional or horizontal/vertical) the task, with respect to its combinatorial nature, can be solved by decomposition methods using heuristic techniques. We present drawbacks of this approach (combinatorial explosion, limited granularity and generating infeasible solutions). Then, using the Voronoi diagrams, we need only polynomial time for finding a solution and, choosing a Euclidean or rectilinear metric, it can be adapted to tasks with general or directional-constrained movements.

Why Is Polonium Simple Cubic and So Highly Anisotropic

Abstract: Using the state-of-the-art ab initio electronic structure calculations, we explain why alpha-Po prefers the simple cubic structure (it is due to the relativistic mass-velocity and Darwin terms), elucidate its extreme elastic anisotropy (this is an intrinsic property of the simple cubic crystal structure), and predict a transformation to a mixture of two trigonal structures at pressures of 1-3 GPa.

PIV Measurement of Separated Flow in a Square Channel With Streamwise Periodic Ribs on One Wall

Abstract: In this study, particle image velocimetry (PIV) is used to investigate the physical process of separated flow in a square channel roughened with periodically transverse ribs on one wall. The ribs obstruct the channel by 15% of its height and are arranged 12 rib heights apart. The Reynolds number, based on the bulk-mean velocity and the corresponding hydraulic diameter of the channel, is fixed at 22,000. Assuming flow periodicity in the streamwise direction, the investigated domain is between two consecutive ribs. The emphasis of this study is to give some insight into the turbulence mechanism associated with separation, reattachment, and subsequent redevelopment. Results are included for mean velocity, friction coefficient, vorticity thickness, Reynolds shear stress, anisotropy parameter, and production of turbulent kinetic energy and shear stress. Based on the two-point correlation profiles, Taylor microscales are derived to reveal the sizes of the turbulence structure in the longitudinal and lateral directions. Moreover, Galilean decomposition is applied to the instantaneous velocity fields. The result shows that the separated shear layer is dominated by the large-scale, unsteady vortical structures.

Stability problems of steel structures in the presence of stochastic and fuzzy uncertainty

Abstract: General ideas and problems of probability approach and its utilization in the verification of structural design procedures of EUROCODES are mentioned. The paper is aimed at the probability study of the ultimate limit state of a steel compressed member designed economically according to EUROCODE 3. The theoretical failure probability (reliability index) vs. ratio of permanent to variable load action is calculated by means of the Monte Carlo simulation method. The misalignment of the failure probability according to EN1990 is analysed. Initial imperfections are generally considered as random variables and random fields. The non-linear beam FEM is used. The influence of initial curvature shape and size variability of the member axis on the variability of load-carrying capacity is investigated. The probabilistic analysis is supplemented with the fuzzy analysis of the influence of uncertainties on the failure probability.