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Found 6289 publications

Error estimation of wavelet based modeling of electromagnetic waves in waveguides and resonators

András Fehér János Pipek Szilvia Nagy

Publication Name: 2nd Middle East Conference on Antennas and Propagation Mecap 2013

Publication Date: 2012-01-01

Volume: Unknown

Issue: Unknown

Page Range: Unknown

Description:

Wavelets provide an effective toolbox for solving differential equations by representing the continuous functions by their wavelet expansion coefficients and the corresponding differential equations by discrete matrix equations. The wavelet basis functions are organized into resolution levels of different frequency terms at different locations, and the main advantage of the wavelet expansion representation is that the resolution level can be different at different locations, if the solution function contains higher frequency terms in one place and restricted to lower frequencies at other places. Wavelet based differential equation solving methods can be adaptive, it is possible to refine the solution locally, if the precision is not sufficient at some regions. In the present work a simple method for estimating the next resolution level wavelet coefficients is presented. Predicting the approximate value of these coefficients makes it possible to select the minimal set of wavelet basis functions for the next resolution level solution in a computationally economic way, or in the last resolution levels it can substitute the next level solution of the matrix equation. © 2012 IEEE.

Open Access: Yes

DOI: 10.1109/MECAP.2012.6618193

Towards the modelling of the fault tolerance mechanism of the PIM-SM multicast routing protocol in an IPTV environment

István Derka Gábor Lencse

Publication Name: Esm 2012 2012 European Simulation and Modelling Conference Modelling and Simulation 2012

Publication Date: 2012-01-01

Volume: Unknown

Issue: Unknown

Page Range: 152-156

Description:

The fault tolerance mechanism of the PIM-SM IP multicast routing protocol is investigated in order to be able to model it. The analysis is done by playing different fault scenarios on a mesh topology multicast test network built up by XORP routers in a virtualized environment. Different parameters of the PIM-SM and the OSPF protocols are examined if they influence and how they influence the outage time of an IPTV service. The results of the experiments provide important factors for building a formal model of the service outage time of an IPTV service. © 2012 EUROSIS-ETI.

Open Access: Yes

DOI: DOI not available

Combining transmission geometry laser ablation and a noncontact continuous flow surface sampling probe/electrospray emitter for mass spectrometry based chemical imaging

Olga S. Ovchinnikova Vilmos Kertesz Gary J. Van Berkel

Publication Name: Rapid Communications in Mass Spectrometry

Publication Date: 2011-12-30

Volume: 25

Issue: 24

Page Range: 3735-3740

Description:

This paper describes the coupling of ambient pressure transmission geometry laser ablation with a liquid-phase sample collection into a continuous flow surface sampling probe/electrospray emitter for mass spectrometry based chemical imaging. The flow probe/emitter device was placed in close proximity to the surface to collect the sample plume produced by laser ablation. The sample collected was immediately aspirated into the probe and onto the electrospray emitter, ionized and detected with the mass spectrometer. Freehand drawn ink lines and letters and an inked fingerprint on microscope slides were analyzed. The circular laser ablation area was about 210 μm in diameter and under the conditions used in these experiments the spatial resolution, as determined by the size of the surface features distinguished in the chemical images, was about 100 μm. Copyright © 2011 John Wiley & Sons, Ltd.

Open Access: Yes

DOI: 10.1002/rcm.5285

Developing sample holders for measuring shielding effectiveness of thin layers on compound semiconductor substrates

András Fehér Szilvia Nagy

Publication Name: Progress in Electromagnetics Research Symposium

Publication Date: 2011-12-26

Volume: Unknown

Issue: Unknown

Page Range: 1637-1641

Description:

Wavelet or multiresolution analysis (MRA) is widely applied in advanced data compression algorithms, solving differential equations, and some approaches have already applied this technique in describing electromagnetic fields. The main advantage of the application of MRA is its adaptivity and flexibility. Since the details of the electromagnetic field are not distributed equally over different parts of the system (i.e., the description of some parts need finer details, while others are easily represented at low resolution level), locally different resolution levels can be applied. Wavelet based adaptive solution possibilities of differential equations of electromagnetic field are investigated in the followings. The adaptivity of the method means in this case, that the refinement level of the solution can be increased locally, if the accuracy needs it, during the calculations. The applicability of the eigenvalue-type differential equation solving method is illustrated by solution of microwave wave-equations of cavity resonators.

Open Access: Yes

DOI: DOI not available

Structural entropy based localization study of wavelet transformed AFM images for detecting background patterns

András Fehér L. M. Molnár Szilvia Nagy

Publication Name: Progress in Electromagnetics Research Symposium

Publication Date: 2011-12-26

Volume: Unknown

Issue: Unknown

Page Range: 1284-1288

Description:

By defining the structural entropy the von Neumann entropy of a charge distribution on a finite grid is divided into two parts. The first one, the extension entropy, is simply the logarithm of the occupation number (i.e., the number of the average grid sites occupied by the charge distribution), while the second part is the structural entropy itself. On a structural entropy versus participation ratio map the different types of localizations follow different, well characterized curves, and every distribution is represented by a vector on the map. By a structural entropy-filling factor map of any charge distributions on a finite grid (e.g., finite representation of an electron density, or a grayscale atomic force microscope (AFM) image) superstructures of different scale topologies with different decay types can be traced as well. However it is rather hard to distinguish elements of an additive superstructure, especially if the numerical parameters of the different scale patterns are necessary. In the AFM practice the background patterns are sometimes hard to compensate, and by simple structural entropy based calculations it is almost impossible to separate the superstructure of the atomic scale and the image-scale pattern. The reason is the following. Superstructures manifest on the structural entropy map as sum of the sub-structures vector, thus since none of the structures are known, only the sum of their vectors, the sub-vectors are not unique. Multiresolution or wavelet analysis (MRA) uses a system of basis functions with various time and frequency (space and spatial frequency) parameters for expanding functions. This system makes the time-frequency localization possible. Using some selected MRA resolution levels of the AFM image and carrying out the structural entropy based localization study on each of these levels will determine the decay type of the image at the length scales corresponding to the selected frequencies. This approach is promising for determining the large-scale patterns on AFM pictures.

Open Access: Yes

DOI: DOI not available

Training electrical engineers on asynchronous logic circuits based on constant weight codes

Gabor Rozsa A. Nagy P. Keresztes László T. Kóczy

Publication Name: IEEE AFRICON Conference

Publication Date: 2011-12-12

Volume: Unknown

Issue: Unknown

Page Range: Unknown

Description:

The paper introduces a new way for teaching of delay insensitive asynchronous logic circuits. The studies start on high level models, which are VHDL implementations of Dennis-type static dataflow systems. Investigating the operation of the concurrent processes of these models, the main elements of the delay insensitive systems can be derived. Introducing constant weight 'm-of-n' codes immediately at the beginning of the course leads to a proper generalization. So the well known dual-rail code circuits can be considered as special cases of the constant weight code delay insensitive circuits. The paper presents briefly the design practice sessions for students. © 2011 IEEE.

Open Access: Yes

DOI: 10.1109/AFRCON.2011.6072041

Predictor set optimization for collaborative filtering

Orsolya Horváth Gabor Takacs

Publication Name: Proceedings of the 6th IEEE International Conference on Intelligent Data Acquisition and Advanced Computing Systems Technology and Applications Idaacs 2011

Publication Date: 2011-12-12

Volume: 1

Issue: Unknown

Page Range: 404-407

Description:

One of the most efficient approaches to create a recommender system is collaborative filtering (CF). CF does not require metadata about users and items, but only interactions between users and items (e.g. ratings), therefore it can be applied in many problem domains. Experience shows that for achieving high accuracy, it is worthwhile to use a blended solution, consisting of many predictors. This paper presents an algorithm for constructing a set of CF predictors so that the overall accuracy of the set is high. The algorithm was tested on the Netflix Prize dataset that contains 100 million ratings. © 2011 IEEE.

Open Access: Yes

DOI: 10.1109/IDAACS.2011.6072784

Adaptive improvement of a passive antilock brake control

J. O. Pedro S. John László T. Kóczy

Publication Name: IEEE AFRICON Conference

Publication Date: 2011-12-12

Volume: Unknown

Issue: Unknown

Page Range: Unknown

Description:

The use of reliable or at least realistic friction models is a key factor in simulation studies related to antilock brake control systems. In the literature a plethora of strongly nonlinear tyre-road friction models are available. Certain models have singular expressions in the arguments of exponential terms in the vicinity of zero car body velocity though this region has practical significance. Since the parameters of these singular models may quickly vary in time with the variation of the road conditions their realtime identification was evaded in a paper that applied a simple observer instead. This method has been improved in the present paper by applying a novel adaptive technique for compensating the effects of the imprecisely known other (i.e. not related to the tyre-road friction) parameters. By the use of a particular friction model it was found via simulations that the adaptive technique can considerably shorten the braking distance. © 2011 IEEE.

Open Access: Yes

DOI: 10.1109/AFRCON.2011.6072040

Variations of gravitation models using geometric programming

Peter Foldesi Habil A. Bako

Publication Name: Isciii 2011 5th International Symposium on Computational Intelligence and Intelligent Informatics

Publication Date: 2011-12-12

Volume: Unknown

Issue: Unknown

Page Range: 93-97

Description:

The article deals with the gravitation problem, which is widely used for solving different practical problems. First of all it is used to forecast the future traffic of a territory (Origin/destination problem). It is also used in the economy for forecasting the Leontief Input/Output table. It will be shown if the I-divergence is used for the sample O/D matrix and the future traffic matrix the cost function is exponential and the element of the forecasted matrix are determined in the well known RAS form. For the proof the geometric programming and its dual and the week and strong duality theorem are applied. © 2011 IEEE.

Open Access: Yes

DOI: 10.1109/ISCIII.2011.6069749