Showing papers by "Brno University of Technology published in 2002"
TL;DR: This work compares maximum axial trapping forces provided by the Gaussian standing-wave trap (SWT) and single-beam trap (SBT) as a function of particle size, refractive index, and beam waist size and shows that the SWT produces axial forces at least ten times stronger and permits particle confinement in a wider range of refractive indices and beam waists compared with those of the SBT.
Abstract: We study the axial force acting on dielectric spherical particles smaller than the trapping wavelength that are placed in the Gaussian standing wave. We derive analytical formulas for immersed particles with relative refractive indices close to unity and compare them with the numerical results obtained by generalized Lorenz-Mie theory (GLMT). We show that the axial optical force depends periodically on the particle size and that the equilibrium position of the particle alternates between the standing-wave antinodes and nodes. For certain particle sizes, gradient forces from the neighboring antinodes cancel each other and disable particle confinement. Using the GLMT we compare maximum axial trapping forces provided by the Gaussian standing-wave trap (SWT) and single-beam trap (SBT) as a function of particle size, refractive index, and beam waist size. We show that the SWT produces axial forces at least ten times stronger and permits particle confinement in a wider range of refractive indices and beam waists compared with those of the SBT.
110 citations
01 Jan 2002
TL;DR: Some disadvantages of present probabilistic models used in EDAs are identified and a more general and efficient model for continuous optimization problems based on the decision trees is proposed.
Abstract: In recent few years expressive progress in the theory and practice of Estimation of Distribution Algorithms (EDA) [1] has appeared, where the classical genetic recombination operators are replaced by probability estimation and stochastic sampling techniques. In this paper we identify some disadvantages of present probabilistic models used in EDAs and propose more general and efficient model for continuous optimization problems based on the decision trees. The new variant of EDA is capable to solve mixed continuous-discrete optimization problems.
89 citations
TL;DR: The ability to form an S-layer appears to be useful as a supportive morphological marker for species classification, with the p6 lattice symmetry appearing to be the most common in cyanobacteria, having been found in 41 out of the 60 S-layers observed.
87 citations
TL;DR: In this paper, modal reflection, transmission and loss of deeply etched Bragg waveguide gratings were modelled by six European laboratories using independently developed two-dimensional numerical codes based on four different methods, with very good mutual agreement.
Abstract: Modal reflection, transmission and loss of deeply etched Bragg waveguide gratings were modelled by six European laboratories using independently developed two-dimensional (2D) numerical codes based on four different methods, with very good mutual agreement. It was found that (rather weak) material dispersion of the SiO2/Si3N4 system does not significantly affect the results. The existence of lossless Floquet-Bloch modes in deeply etched gratings was confirmed. Based on reliable numerical results, the physical origin of out-of-plane losses of 1D or 2D photonic band gap structures in slab waveguides is briefly discussed.
78 citations
TL;DR: A helical coupling plasma system for continuous surface treatment and modification (surface processing) of fiber bundles has been developed and tested for glass fibers as mentioned in this paper, which enables surface processing of single filaments and flat substrates as well.
Abstract: New helical coupling plasma system for continuous surface treatment and modification (surface processing) of fiber bundles has been developed and tested for glass fibers. The system enables surface processing of single filaments and flat substrates as well. Surface processed glass fibers and their bundles were examined as reinforcements for glass fiber/polyester composite systems. Processing of fibers comprised a surface treatment using argon gas and a surface modification using hexamethyldisiloxane and vinyltriethoxysilane monomers. Interfacial and interlaminar shear strengths of plasma processed glass fiber/polyester systems were compared with those of untreated and commercially sized fibers.
76 citations
TL;DR: A new approach to automatic design of image filters for a given type of noise is introduced that employs evolvable hardware at simplified functional level and produces circuits that outperform conventional designs.
Abstract: The paper introduces a new approach to automatic design of image filters for a given type of noise. The approach employs evolvable hardware at simplified functional level and produces circuits that outperform conventional designs. If an image is available both with and without noise, the whole process of filter design can be done automatically, without influence of a designer.
69 citations
TL;DR: In this paper, the effect of the shape and size of bodies on the process of binder removal was examined and the formation of defects due to non-uniform binder distribution was described and requirements for their elimination were proposed.
Abstract: Thermal removal of polymer binder containing low-molecular-weight components from ceramic injection mouldings was studied. The effect of the shape and size of bodies on the process of binder removal was examined. Evaporation of low-molecular-weight components represented the most important process at the beginning of binder removal. It was found that a bed of activated carbon speed up removal of low-molecular-weight components. The mechanism of binder removal in a bed of activated carbon was described. Binder redistribution and evolution of porosity in the body during binder removal was investigated. A high rate of binder removal resulted in non-uniform binder distribution in the body. The formation of defects due to non-uniform binder removal was described and requirements for their elimination were proposed.
69 citations
TL;DR: Following the previous results for the wave equation system, approximate evolution operators for the linearized Euler equations are derived and error estimates for the finite volume evolution Galerkin scheme for linear systems with constant coefficients are proved.
55 citations
07 Aug 2002
TL;DR: The original newly introduced method considerably simplifies the setting and realization of fuzzy PI/PD/PID controllers.
Abstract: Fuzzy PID controllers are physically related to classical PID controller. The parameters settings of classical and fuzzy controllers are based on deep common physical background. The original newly introduced method considerably simplifies the setting and realization of fuzzy PI/PD/PID controllers.
55 citations
TL;DR: In this article, a capillary discharge soft X-ray laser operating at 46.9 rim on the transition 3p-3s (J=0−1) of the Ne-like Ar has been realized by exciting the active medium with a long half-cycle duration current pulse of 140 ns.
Abstract: A capillary discharge soft X-ray laser operating at 46.9 rim on the transition 3p–3s (J=0−1) of the Ne-like Ar has been realized by exciting the active medium with a long half-cycle duration current pulse of 140 ns. The current is produced by discharging a 10 nF water dielectric capacitor, initially charged to voltages lower than 200 kV by a six stage Marx generator, through a 15-cm long capillary channels. The laser amplification has been obtained by properly adjusting all the other experimental parameters. Utilizing a 3-mm in diameter AI2O3 capillary channel initially filled with 0.3 torr of Ar pressure, a laser beam, which has a 4-mrad divergence and a time duration of 1.3 ns, is characterized by a gain of 0.6 ± 0.1 cm−1. The stability of the plasma compression followed by the laser emission is verified.
52 citations
TL;DR: In this paper, the most commonly used epoxy-based adhesive EPOXY 371 has maintained the shear properties without great changes in all environments, also with other type of primer (P11), and exhibited the best shear strength in cool water.
04 Sep 2002
TL;DR: A novel list-based scheduling algorithm based on incorporating some information extracted from data flow graph (DFG) structure to guide the scheduler to find near-optimal/optimal schedules quickly.
Abstract: Scheduling is considered as the most important task in high-level synthesis process. This paper presents a novel list-based scheduling algorithm based on incorporating some information extracted from data flow graph (DFG) structure to guide the scheduler to find near-optimal/optimal schedules quickly. We have developed a novel approach based on DFG analysis that is totally done as preparation phase. This DFG analysis information includes: every node knows its successor and its predecessor, total number of successors, and the tree which it belongs to, where trees are constructed from every output operation from the constructed DFG. Incorporating this knowledge in the priority functions of the scheduler guided the scheduler to make the correct choice of the perfect operation to be scheduled next.
TL;DR: The association between neural models and genetic algorithms, which can provide a global design tool, is discussed and portions of the MATLAB code illustrate the descriptions.
Abstract: Neural networks are systems that can be trained to remember the behavior of a modeled structure at given operational points, and that can be used to approximate the behavior of the structure outside of the training points. These neural-net approximation abilities are demonstrated in the modeling a frequency-selective surface, a microstrip transmission line, and a microstrip dipole. Attention is given to the accuracy and to the efficiency of neural models. The association between neural models and genetic algorithms, which can provide a global design tool, is discussed. Portions of the MATLAB code illustrate the descriptions.
TL;DR: In this article, the authors presented a numerically exact and simple technique for the determination of leaky modes in planar multilayer waveguides using a dispersion equation provided by the thin-film transfer matrix method.
Abstract: In this letter, we present a numerically exact and simple novel technique for the determination of leaky modes in planar multilayer waveguides. The technique uses a dispersion equation provided by the thin-film transfer matrix method. Complex roots, that correspond to leaky modes, are searched on the basis of a smooth transition between the bound modes of a closed waveguide and the leaky modes of an open waveguide. The technique does not use any approximation.
24 Apr 2002
TL;DR: The contribution addresses issues, general development in the area, and shows examples of hardware platforms and algorithms that can be implemented on FPGA platforms, e.g. VHDL.
Abstract: Computer graphics algorithms and algorithms used in image processing are generally computationally expensive. This fact is the reason why people struggle to accelerate such algorithms using any reasonable means. The traditional sources of speedup are faster processors, parallelism, or dedicated hardware. Development in digital circuit technology, especially rapid development of Field Programmable Gate Arrays (FPGA), offers alternative way to acceleration. Current FPGA chips are capable of running graphics algorithms at the speed comparable to dedicated graphics chips. At the same time they are configurable not only using schematics diagram but also through high-level programming languages, e.g. VHDL. The contribution addresses these issues, general development in the area, and shows examples of hardware platforms and algorithms that can be implemented on such platforms.
TL;DR: In this article, a series of low-molecular-mass fluorescent ampholytes with narrow pI range were presented for detection compatible with argon laser-induced fluorescence (LIF) detection.
Abstract: We prepared a series of low-molecular-mass fluorescent ampholytes with narrow pI range. These fluorescein-based ampholytes are detection compatible with argon laser-induced fluorescence (LIF) detection. The selected properties, important for their routine use as fluorescent pI markers, were examined. The pI values of new fluorescein-based pI markers were determined by capillary isoelectric focusing (CIEF) using currently available low-molecular-mass pI markers for CIEF with photometric detection. The examples of CIEF with fluorometric detection of new compounds together with fluorescein isothiocyanate (FITC) derivatized proteins are presented.
Abstract: SUMMARY The aim of this paper is a derivation of a new multidimensional high-resolutionnite volume evolution Galerkin method for system of the Euler equations of gas dynamics. Instead of solving one-dimensional Riemann problems in directions normal to cell interfaces thenite volume evolution Galerkin schemes are based on a genuinely multidimensional approach. The approximate solution at cell interfaces is com- puted by means of an approximate evolution operator taking all of the innitely many bicharacteristics explicitly into account. Integrals along the Mach cones are evaluated exactly or by means of numerical quadratures. Second-order resolution is obtained with a conservative piecewise bilinear recovery and the second-order midpoint rule for the time integration. A numerical experiment which illustrates the good multidimensional approximation as well as higher-order resolution is presented. Copyright ? 2002 John Wiley & Sons, Ltd.
23 Oct 2002
TL;DR: The proposed method is based on registering both (very different) images using mutual information as the coincidence measure to join the image data produced by the Heidelberg Retina Tomograph and the standard colour photograph.
Abstract: Registration of retinal images provided by different modalities is required to facilitate diagnosis of the optic nerve head and retina. For reliable automatic segmentation of the optic disk, it seems essential to join the image data produced by the Heidelberg Retina Tomograph (HRT) and the standard colour photograph. The proposed method is based on registering both (very different) images using mutual information as the coincidence measure.
TL;DR: An overview of optical and electrical properties of organic solids, low-molecular-weight materials and polymers is presented in this paper, starting with 3D organosilicon structures, incorporating one-dimensionality of silicon polymers and is extended to π-conjugated materials.
Abstract: An overview of optical and electrical properties of organic solids, low-molecular-weight materials and polymers is presented. The discussion starts with 3D organosilicon structures, incorporates one-dimensionality of silicon polymers and is extended to π-conjugated materials. Many electronic processes of organic semiconductors result directly from properties of the constituent molecules; thus, one may envisage the possibility of constructing molecular-scale electronic devices.
01 Jan 2002
TL;DR: The aim of this paper is to test the efficiency of new approaches for discrete combinatorial problems represented by hypergraph partitioning by implementing a simple GA based on the GaLib library and extending the BMDA algorithm to a new version with finite alphabet encoding of chromozomes and new metric that enables the m-way partitioning graphs.
Abstract: This paper is an experimental study on hypegraph partitioning using the simple genetic algorithm (GA) based on the schema theorem and the advanced algorithms based on the estimation of distribution of promising solution. Primarily we have implemented a simple GA based on the GaLib library[Gal94] and some hybrid variant included a fast heuristics to speed up the convergence of the optimization process. Secondly we have implemented the Univariate Marginal Distribution algorithm (UMDA) and the Bivariate Marginal Distribution algorithm (BMDA), both have been published even recently[Pel98] and used a share version of a superior new program BOA based on the Bayesian Optimization Algorithm [Pel99]. We have also extended the BMDA algorithm to a new version with finite alphabet encoding of chromozomes and new metric that enables the m-way partitioning graphs. The aim of our paper is to test the efficiency of new approaches for discrete combinatorial problems represented by hypergraph partitioning.
TL;DR: In this article, the solutions of three models of reaction kinetics in HV circuit breakers with SF6 after current zero are presented and compared and general conclusions have been derived from the comparison.
Abstract: In this paper, the solutions of three models of reaction kinetics in HV circuit breakers with SF6 after current zero are presented and compared. One model has been proposed by Bartlova, the co-author of this paper, the other two models under comparison have been taken over from the literature. In all the three models a constant pressure p(t) = 4 atm and the same dependence of temperature on time T(t) are assumed. For the description of the relation between equilibrium and kinetic composition in a system, the concept of asymptotic composition is introduced. A comparison of the composition and enthalpy of the products of SF6 dissociation and ionization for the given pressure and T(t) is made. General conclusions have been derived from the comparison.
TL;DR: In this paper, the current distribution over the plate surface in lead-acid cells in the course of discharge was determined mathematically by using the equivalent circuit method, and the dependence of the internal cell resistance on the current and charge passed was determined by measurements on a laboratory cell.
TL;DR: In this paper, the convergence of all solutions of the scalar equation x = f(t,x t ) under the main assumption that every constant is its solution is studied and the criterion and the sufficient conditions for convergence are proved.
TL;DR: In this paper, Ceria powder was dry-milled to sub-micrometric particle sizes and used in the preparation of ceramic mixture for injection molding, and the bodies were injection moulded in the shape of rectangular bars.
TL;DR: In this paper, the influence of reaction conditions (temperature, type of catalyst, time) on the base-catalyzed reaction of mono-, di-, and trialkylphosphates with Ca2+ ions and on the structure and composition of the reaction products was studied.
Abstract: The influence of reaction conditions (temperature, type of catalyst, time) on the base-catalyzed reaction of mono-, di-, and trialkylphosphates (alkyl = methyl, ethyl, i-propyl, n-butyl) with Ca2+ ions and on the structure and composition of the reaction products was studied. The composition of the calcium phosphates depends mainly on the reaction temperature. At temperatures below 100°C, a nanocrystalline solid product transforming into dicalcium phosphate by heating (calcination) was found. Pure nanocrystalline hydroxyapatite was prepared by hydrothermal synthesis at 160°C from mono- and dialkylphosphates. The size of hydroxyapatite crystallites was about 1 nm, the particle size about 150 nm. Agglomerated particles of hydroxyapatite larger than 2 µm were prepared at 200°C. Hydrothermal reaction of trialkylphosphates with Ca2+ ions at 200°C produced CaHPO4. The experimental results were used to propose a reaction mechanism for base-catalyzed hydrothermal reactions of alkylphosphates with Ca2+ ions.
07 Aug 2002
TL;DR: In this article, the authors deal with the transformation of networks in the familiar voltage signal processing mode (VM) into the equivalent current mode (CM) and present an adjoint VM-CM transformation of the circuits, containing several modern multi-port current conveyors.
Abstract: The paper deals with the transformation of networks in the familiar voltage signal processing mode (VM) into the equivalent current mode (CM). The adjoint VM-CM transformation of the circuits, containing several modern multi-port current conveyors, is given. An example of adjoint VM and CM biquadratic ARC filters, using differential voltage current conveyors (DVCC), illustrates this transformation.
29 Jul 2002
TL;DR: In this paper, the authors describe a new laser head with Vertical Cavity Surface Emitting Laser (VCSEL) diode for absolute laser interferometry with Michelson interferometer.
Abstract: We describe a new laser head with Vertical Cavity Surface Emitting Laser (VCSEL) diode for absolute laser interferometry with Michelson interferometer. The VCSEL lasers at 760 rim with mode-hop free tuning range above 1 nm are affordable now. The VCSEL's are fabricated as circulary-symetric lasers; the circular aperture is of particular value as it implies a circular beam profile. The linewidth and the optical noise of the VCSEL laser diode depend on the stability of the current source controller and on the quality temperature control system. We developed a digital temperature control system with temperature stability below 1 mK and high stability current source controller.
TL;DR: In this article, a two-state model of stochastic generation-recombination process has been elaborated for the two-level impulse noise allowing to derive some statistical characteristics of this process.
Abstract: Random two-level or multiple-level current impulses may occur in electronic devices containing reverse biased p-n junctions in a certain operating mode. These impulses are usually rectangular, featuring constant amplitude, random pulse width and pulse origin time points. This phenomenon is generally ascribed to local avalanche breakdowns originating in p-n junction defect regions called microplasma regions. Based on experiment results, a two-state model of stochastic generation-recombination process has been elaborated for the two-level impulse noise allowing to derive some statistical characteristics of this process. It can be shown that the distribution of the probability density w(τ0) of the impulse separation τ0 and the probability density w(τ1) of the impulse width τ1 have exponential courses. The power spectral density of the noise current is of a G-R process type and depends on the particular microplasma properties. From the viewpoint of noise diagnostics, the most important features are the spectral density Su and noise current IN versus reverse current IR plots, because each local extreme of these plots corresponds to an active microplasma region. Thus obtained results may be used for p-n junction non-destructive diagnostics and quality assessment.
TL;DR: In this paper, the spectral dependence of the refractive index of the material forming the film is determined using variable-angle spectroscopic ellipsometry (VASE), which is then used to evaluate the values of the thickness along the area of the non-uniform film under investigation.
Abstract: An original method enabling us to characterize the non-uniformity of thin-film thickness is described. This method employs the interpretation of data obtained by multiple-wavelength reflectometry (MWR). Within this MWR method the values of the reflectance are measured for several wavelengths in many points lying along the area of the film. The spectral dependence of the refractive index of the material forming the film is determined using variable-angle spectroscopic ellipsometry (VASE). The MWR method is then used to evaluate the values of the thickness along the area of the non-uniform film under investigation. Within the experimental set-up employed for applying the MWR method, a multi-wavelength laser is used as a light source. A CCD camera equipped with a zoom objective is utilized as a detector. A suitable beamsplitter allows to measure the values of the relative reflectance of the film against a reference sample with known reflectance. By using the set-up employed it is possible to characterize the thin-film spreading over large areas of substrates.
TL;DR: In this paper, a laboratory experimental device was developed to allow full-scale measurements on roll cooling to be carried out, which can help in "making a decision" related to a prior plant application.