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Hopp T.,Karlsruhe Institute of Technology | Sroba L.,Slovak University of Technology | Zapf M.,Karlsruhe Institute of Technology | Dapp R.,Karlsruhe Institute of Technology | And 3 more authors.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2014

Ultrasound Computer Tomography (USCT) is a promising modality for breast imaging. We developed and tested the first full 3D USCT system aimed at in-vivo imaging. It is based on approx. 2000 ultrasound transducers surrounding the breast within a water bath. From the acquired signal data, reflectivity, attenuation and sound speed images are reconstructed. In a first in-vivo study we imaged ten patients and compared them to MRI images. To overcome the considerably different breast positioning in both imaging methods, an image registration and image fusion based on biomechanical modeling of the buoyancy effect and surface-based refinement was applied. The resulting images are promising: compared with the MRI ground truth, similar tissue structures can be identified. While reflection images seem to image even small structures, sound speed imaging seems to be the best modality for detecting cancer. The registration of both imaging methods allows browsing the volume images side by side and enables recognition of correlating tissue structures. The first in-vivo study was successfully completed and encourages for a second in-vivo study with a considerably larger number of patients, which is currently ongoing. © 2014 Springer International Publishing. Source

Margetin M.,Slovak University of Technology | Durka R.,R.O.S.A. | Chmelko V.,Slovak University of Technology
Frattura ed Integrita Strutturale | Year: 2016

Multiaxial high cycle fatigue is a topic that concerns nearly all industrial domains. In recent years, a great deal of recommendations how to address problems with multiaxial fatigue life time estimation have been made and a huge progress in the field has been achieved. Until now, however, no universal criterion for multiaxial fatigue has been proposed. Addressing this situation, this paper offers a design of a new multiaxial criterion for high cycle fatigue. This criterion is based on critical plane search. Damage parameter consists of a combination of normal and shear stresses on a critical plane (which is a plane with maximal shear stress amplitude). Material parameters used in proposed criterion are obtained from torsion and axial S-N curves. Proposed criterion correctly calculates life time for boundary loading condition (pure torsion and pure axial loading). Application of proposed model is demonstrated on biaxial loading and the results are verified with testing program using specimens made from S355 steel. Fatigue material parameters for proposed criterion and multiple sets of data for different combination of axial and torsional loading have been obtained during the experiment. © 2016, Gruppo Italiano Frattura. All rights reserved. Source

Rabcan J.,Slovak University of Technology | Grmanova G.,Slovak University of Technology
Journal of Theoretical and Applied Information Technology | Year: 2016

Bag of Visual Words is a common representation of images in computer vision. The important task for this representation is a creation of visual codebook, where the set of all considerable visual words is stored. Visual words are represented by descriptors of local features and to reduce their amount and to choose only significant ones, the visual codebook is generated by clustering of these descriptors. State of the art for clustering descriptors of local features is k-menas algorithm. The drawback of codebook generation by kmeans algorithm is that cluster centers are located in high density areas. In this paper, we investigate several other algorithms and we compare them with k-menas algorithm. Tested algorithms are similar to k-means in their goals, but have algorithmically different approaches. Comparison is done by evaluating of image retrieval task on UK-bench dataset and classification on Caltech 101. © 2005 - 2015 JATIT & LLS. All rights reserved. Source

Linder M.,Slovak University of Technology | Sekaj I.,Slovak University of Technology
Mendel | Year: 2011

Parallel genetic algorithms (PGA) can significantly improve the performance of genetic algorithms (GA). Therefore we have analyzed the influence of various parallel genetic algorithm architectures on the algorithm convergence rate. Several Coarse-grained PGA and Fine-grained PGA architectures are compared. From the important factors we selected the following: structure of the migration interconnections, number of migration interconnections and migration size. The performance of selected PGAs is demonstrated on test function minimisation experiments. Source

Vozak D.,Slovak University of Technology | Vesely V.,Slovak University of Technology
Proceedings of the 2013 International Conference on Process Control, PC 2013 | Year: 2013

The paper presents two methods of robust output feedback controller design for MIMO systems. First is based on solving bilinear matrix inequalities (BMI) and second uses linearisation to transform problem into linear matrix inequality (LMI). Both methods can be applied to continuous or discrete time systems. In order to test the applicability, a set of randomly generated unstable systems was created. Then the number of successfully solved systems and time required to solve the problem is compared. Although the LMI method is only heuristic experiments showed that it has better results and can be used with higher order systems. © 2013 IEEE. Source

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