Showing papers by "Brno University of Technology published in 2009"

SPICE Model of Memristor with Nonlinear Dopant Drift

Abstract: A mathematical model of the prototype of memristor, manufactured in 2008 in Hewlett-Packard Labs, is described in the paper. It is shown that the hitherto published approaches to the modeling of boundary conditions need not conform with the requirements for the behavior of a practical circuit element. The described SPICE model of the memristor is thus constructed as an open model, enabling additional modifications of non-linear boundary conditions. Its functionality is illustrated on computer simulations.

Quantum Dots — Characterization, Preparation and Usage in Biological Systems

Abstract: The use of fluorescent nanoparticles as probes for bioanalytical applications is a highly promising technique because fluorescence-based techniques are very sensitive. Quantum dots (QDs) seem to show the greatest promise as labels for tagging and imaging in biological systems owing to their impressive photostability, which allow long-term observations of biomolecules. The usage of QDs in practical applications has started only recently, therefore, the research on QDs is extremely important in order to provide safe and effective biosensing materials for medicine. This review reports on the recent methods for the preparation of quantum dots, their physical and chemical properties, surface modification as well as on some interesting examples of their experimental use.

Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae

Abstract: We systematically surveyed period variations of superhumps in SU UMa-type dwarf novae based on newly obtained data and past publications. In many systems, the evolution of superhump period are found to be composed of three distinct stages: early evolutionary stage with a longer superhump period, middle stage with systematically varying periods, final stage with a shorter, stable superhump period. During the middle stage, many systems with superhump periods less than 0.08 d show positive period derivatives. We present observational characteristics of these stages and greatly improved statistics. Contrary to the earlier claim, we found no clear evidence for variation of period derivatives between superoutburst of the same object. We present an interpretation that the lengthening of the superhump period is a result of outward propagation of the eccentricity wave and is limited by the radius near the tidal truncation. We interpreted that late stage superhumps are rejuvenized excitation of 3:1 resonance when the superhumps in the outer disk is effectively quenched. The general behavior of period variation, particularly in systems with short orbital periods, appears to follow the scenario proposed in Kato et al. (2008). We also present an observational summary of WZ Sge-type dwarf novae. Many of WZ Sge-type dwarf novae showed long-enduring superhumps during the post-superoutburst stage having periods longer than those during the main superoutburst. The period derivatives in WZ Sge-type dwarf novae are found to be strongly correlated with the fractional superhump excess, or consequently, mass ratio. WZ Sge-type dwarf novae with a long-lasting rebrightening or with multiple rebrightenings tend to have smaller period derivatives and are excellent candidate for the systems around or after the period minimum of evolution of cataclysmic variables.

Comparison of scoring methods used in speaker recognition with Joint Factor Analysis

Abstract: The aim of this paper is to compare different log-likelihood scoring methods, that different sites used in the latest state-of-the-art Joint Factor Analysis (JFA) Speaker Recognition systems. The algorithms use various assumptions and have been derived from various approximations of the objective functions of JFA. We compare the techniques in terms of speed and performance. We show, that approximations of the true log-likelihood ratio (LLR) may lead to significant speedup without any loss in performance.

Atmospheric effects on availability of free space optics systems

Abstract: The availability of free space optics (FSO) systems in dependence on weather conditions and on FSO link parameters, such as transmitted optical power, beam divergence, receiver sensitivity or link path distance, is discussed. A number of phenomena in the atmosphere, such as absorption, scattering, and turbulence, can affect beam attenuation, but in the case of wavelengths typical of FSO systems operation, only scattering and turbulence are appropriate to be taken into consideration. We model the power loss caused by turbulence by using the Rytov scintillation theory. Attenuation due to scattering, which can be expressed as a function of the link distance, wavelength, and meteorological visibility, is calculated from visibility data collected at several airports in Europe. Statistical evaluation of the attenuation caused by scattering and the power link margin calculated from FSO link parameters are used for calculating the link availability.

Preparation and Properties of Various Magnetic Nanoparticles

Abstract: The fabrications of iron oxides nanoparticles using co-precipitation and gadolinium nanoparticles using water in oil microemulsion method are reported in this paper. Results of detailed phase analysis by XRD and Mossbauer spectroscopy are discussed. XRD analysis revealed that the crystallite size (mean coherence length) of iron oxides (mainly γ-Fe2O3) in the Fe2O3 sample was 30 nm, while in Fe2O3/SiO2 where the e-Fe2O3 phase dominated it was only 14 nm. Gd/SiO2 nanoparticles were found to be completely amorphous, according to XRD. The samples showed various shapes of hysteresis loops and different coercivities. Differences in the saturation magnetization (MS) correspond to the chemical and phase composition of the sample materials. However, we observed that MS was not reached in the case of Fe2O3/SiO2, while for Gd/SiO2 sample the MS value was extremely low. Therefore we conclude that only unmodified Fe2O3 nanoparticles are suitable for intended biosensing application in vitro (e.g. detection of viral nucleic acids) and the phase purification of this sample for this purpose is not necessary.

Support vector machines and Joint Factor Analysis for speaker verification

Abstract: This article presents several techniques to combine between Support vector machines (SVM) and Joint Factor Analysis (JFA) model for speaker verification. In this combination, the SVMs are applied to different sources of information produced by the JFA. These informations are the Gaussian Mixture Model supervectors and speakers and Common factors. We found that using SVM in JFA factors gave the best results especially when within class covariance normalization method is applied in order to compensate for the channel effect. The new combination results are comparable to other classical JFA scoring techniques.

Neural network based language models for highly inflective languages

Abstract: Speech recognition of inflectional and morphologically rich languages like Czech is currently quite a challenging task, because simple n-gram techniques are unable to capture important regularities in the data. Several possible solutions were proposed, namely class based models, factored models, decision trees and neural networks. This paper describes improvements obtained in recognition of spoken Czech lectures using language models based on neural networks. Relative reductions in word error rate are more than 15% over baseline obtained with adapted 4-gram backoff language model using modified Kneser-Ney smoothing.

Investigation into bottle-neck features for meeting speech recognition.

Abstract: This work investigates into recently proposed Bottle-Neck features for ASR. The bottle-neck ANN structure is imported into Split Context architecture gaining significant WER reduction. Further, Universal Context architecture was developed which simplifies the system by using only one universal ANN for all temporal splits. Significant WER reduction can be obtained by applying fMPE on top of our BN features as a technique for discriminative feature extraction and further gain is also obtained by retraining model parameters using MPE criterion. The results are reported on meeting data from RT07 evaluation.

Antioxidant activity of phenolic acids in lipid oxidation catalyzed by different prooxidants.

Abstract: The antioxidant activity of three naturally occurring phenolic acids, caffeic (CaA), ferulic (FeA), and p-coumaric acid (CoA), and a synthetic compound, propyl gallate (PG), was evaluated in a food-related model system, a liposome dispersion of marine polyunsaturated fatty acids Oxidation was induced by two different prooxidants, free iron ions and bovine hemoglobin (Hb) Continuous measurement of oxygen uptake was used to quantify the rate of lipid oxidation at steady state Free iron-induced oxidation was reduced in the following order: PG > FeA > CoA Caffeic acid worked as a prooxidant and increased the oxidation rate by a factor of 9 For Hb-induced oxidation, the relative efficiency was PG > CaA ∼ FeA ≫ CoA The antioxidant activity was also evaluated by four antioxidant capacity assays In the Folin−Ciocalteu, ferric reducing/antioxidant power, and 2,2-diphenyl-1-picrylhydrazyl radical scavenging assays, the antioxidant activity followed the sequence PG > CaA > FeA > CoA The order for the 2,2′-az

Extrusions and intrusions in fatigued metals. Part 2. AFM and EBSD study of the early growth of extrusions and intrusions in 316L steel fatigued at room temperature

Abstract: Early stages of surface relief evolution of persistent slip markings (PSMs), formed in areas where persistent slip bands (PSBs) intersect the free surface, in polycrystalline 316L stainless steel cycled with constant plastic strain amplitude were studied using atomic force microscopy (AFM) and electron backscattering diffraction (EBSD). Focused ion beam (FIB) technique was employed to obtain additional, more detailed information on the shape of PSMs. To reveal true qualitative and quantitative information on the simultaneous growth of intrusions and extrusions within individual PSMs, identical areas both on the specimen surface and on its inverse copy obtained via plastic replica were studied using AFM. Intrusions are preceded by extrusions regardless of orientation of individual grains of the polycrystal. The first intrusions appear largely around 1% of fatigue life at the moment when ‘static’ extrusions are developed. They appear predominantly but not exclusively at the side of extrusions where the emer...

Material and geometrical characteristics of structural steels based on statistical analysis of metallurgical products

Abstract: The experimental research results of material and geometrical characteristics of Czech steel are given in the presented paper. Measurements are carried out for the yield strength of plates made of steel grade S355. The values measured are used to compute axial resistances which are compared with the resistance resulting from standard (nominal) values. In this paper, there was used a statistical information for evaluating the results of strength measurements on a series of plates and hot‐rolled profiles under tension to determine the adequate partial γM0 safety factor.

Phase correlation method for the alignment of total solar eclipse images

Abstract: A modified phase correlation method, based on Fourier transform, which enables the alignment of solar coronal images taken during the total solar eclipses, is presented. The method enables the measurement of translation, rotation, and scaling factor between two images. With the application of this technique, pairs of images with different exposure times, different brightness scale, such as linear for CCD and nonlinear for images taken with photographic film, and even images from different emission lines can be aligned with sub-pixel precision.

Brno University of Technology system for Interspeech 2009 emotion challenge.

Abstract: This paper describes Brno University of Technology (BUT) system for the Interspeech 2009 Emotion Challenge. Our submitted system for the Open Performance Sub-Challenge uses acoustic frame based features as a front-end and Gaussian Mixture Models as a back-end. Different feature types and modeling approaches successfully applied in speakerand language recognition are investigated and we can achieve an 16% and 9% relative improvement over the best dynamic and static baseline system on the 5-class task, respectively.

Efficient 2-D Integral Equation Approach for the Analysis of Power Bus Structures With Arbitrary Shape

Abstract: A 2-D contour integral-equation method for the frequency-domain analysis of arbitrarily shaped power bus structures is presented. The numerically efficient approach allows the rapid and accurate computation of the frequency-dependent transfer parameters between an arbitrary number of ports, as required for embedding the power plane structure into network simulation. A formulation is developed for calculating the voltage distribution between the planes, as well as for determining the resulting radiated fields based on the field-equivalence principle. The method is applied for several test boards including a populated board with a surface-mount decoupling-capacitor network. The suggested approach is well confirmed by an analytical solution for the rectangular structure, by measurement and 3-D full-wave simulation results.

Dynamic Behavior Modeling and Verification of Advanced Electrical-Generator Set Concept

Abstract: Current development trends regarding mobile electrical-generator sets (EGSs) indicate that enhancement of efficiency is to be sought in means to operate the driving engine (either diesel or gasoline) continuously at its optimum speed. The engine-generator dynamics at a sudden load change (from low load to high load) remains a challenge in this regard. The dynamic behavior analysis presented here proves that the introduction of an energy storage element into the EGS with variable-engine-speed concept eliminates this drawback. This paper addresses the identification of the dynamic behavior of such variable-speed EGS systems and the problems encountered during a sudden increase of load (power and voltage drops).

Amino acid and soluble protein cocktail from waste keratin hydrolysed by a fungal keratinase of Paecilomyces marquandii

Abstract: Waste bovine hooves and horns were enzymatically hydrolysed into soluble products intended for foliar fertilizer. With the powdered keratin at 50°C and pH 8 between 34 to nearly 60% of nitrogen was solubilized in 5 h, depending on the enzyme concentration. The reaction could further be improved by steam pretreatment of the keratin, resulting in 98% solubilisation of the nitrogen. The products of hydrolysis consisted of a mixture of soluble proteins, peptides, and free amino acids. Among the latter, 18 common amino acids were detected. Several of them were previously recognized to have a positive effect on plants. Nonpolar neutral, basic, and sulphur amino acids were present in relatively large amounts, while proline and tryptophan were not found. Comparison with other protein hydrolysates aimed for fertilizer suggests that keratin degradation products, obtained by enzymatic hydrolysis, have potential to be used for foliar fertilization, alone or in a combination with another complementary hydrolysate of a different source, such as skin or plant proteins.