Abstract: The main subject of the study, which is summarized in this article, was to compare three different models of neural networks (Linear Neural Unit (LNU), Quadratic Neural Unit (QNU) and Multi-Layer Perceptron Network (MLP)) to identify of the real system of the manipulator arm. The arm is powered by FESTO fluidic muscles, which allows for two degrees of freedom. The data obtained by the measurements were processed in Python. This program served as a tool for compiling individual dynamic models, predicting measured data, and then graphically interpreting the resulting models. Levenberg-Marquardt (LM) was used as the learning algorithm because it is more suitable for learning neural networks than for example, the Gauss-Newton method.

Keywords: pneumatic artificial muscle (PUS); learning algorithm; neural network; identification; manipulator; fluid muscles; Python

Abstract: The aim of this study was to analyze the reliability of texture index (TI) calculations using two different approaches. First, we calculated texture parameters on synthetically constructed images using four different biomedical software tools (CGITA, InterView Fusion, Matlab, MaZda). Second, we investigated the reliability of texture parameters, particularly how the texture indices diverge between two similar images with substantially different texture. We generated five different heterogeneous synthetic images, thereafter, histogram-based and co-occurrence matrix features were calculated. The co-occurrence based indices were computed after two (8 and 64) different gray scale normalizations. For the reliability test, we compared 22 texture indices using a histological slice of the brain and Michelangelo's painting, and the gray level dependence was also analyzed. The histogram-based parameters of all images and from all software were very similar. Differences were found in the co-occurrence based indices after both gray level image normalizations. The reliability tests showed that from 22 parameters only 5 texture indices changed more than 20%, and at least 64 normalization levels were necessary for acceptable results. Our results underline that in medical multicenter studies it is especially critical to use the same software package. Some parameters do not reliably reflect changes, so texture analysis (TA) should be used with caution.

Keywords: texture analysis; medical imaging; software; comparative study; co-occurrence matrix

Abstract: This article presents calculations and visualization of an electric field of a point charge (equipotential lines) and systems of oppositely charged threads, of magnetic field lines of a thin long and straight current-carrying conductor, magnetic field lines inside a cylindrical conductor with evenly distributed current made using the MATLAB language. Calculations of an electric field and potential of a point charge as a function of a distance are provided as well as a potential of a system of oppositely charged threads, magnetic induction of a thin, long current-carrying conductor as a function of a distance and magnetic induction inside the cylindrical conductor are performed. The graphs of these dependencies are drawn.

Keywords: cylindrical conductor; electric field; equipotential lines; magnetic induction; point charge

Abstract: The aim of the current study is to reveal the types of connections between spatial ability and visual imagery preferences. Participants in the study were 114 students from five Universities in Hungary. Two measurement tools were administered: (1) The OSIQ questionnaire (30 items, 15 items on object imagery, and 15 on spatial imagery), and (2) A spatial ability test. The score achieved on spatial imagery items of the OSIQ test has a significant correlation with performance on the spatial ability test (r = 0.46; p < 0.001), while score on the object imagery items has a neutral correlation with spatial ability (r = -0.07; p = 0.46). This tendency in the strengths of correlations was independent of the type of study (engineering students and visual art pre-service teachers) and of gender. Results have relevance for designer training, skills identification and talent identification.

Keywords: spatial ability; visual imagery; OSIQ; visual skills development

Abstract: This paper analyzes the properties of Catalan numbers and their relation to the Lattice Path combinatorial problem in cryptography. Specifically, analyzes the application of the appropriate combinatorial problem based on Catalan-key in encryption and decryption of files and plaintext. Accordingly, we use Catalan numbers for generating keys and within the experimental part we have applied the NIST (National Institute of Standards and Technology) statistical battery of tests for assessing the quality of generated keys was applied. A total of 12 quality assurance tests for Catalan-key were applied. A Java application is presented which allows the encryption and decryption of plaintext based on the generated Catalan-key and combinatorial problem of movement in integer network or Lattice Path. Experimental study yields the comparison of results in text encryption speed for combinatorial encryption methods (such as: Ballot Problem, Stack permutations and Balanced Parentheses) in comparison with Lattice Path method (in Java programming language).

Keywords: cryptography; Catalan numbers; Lattice path; combinatorial problems; encryption

Abstract: Ultrasound is one of the most widely employed real-time diagnostic imaging modalities in modern medicine. To use it efficiently, and to correctly interpret the images, the medical staff needs to acquire sophisticated skills. In this article, a review is provided on the devices and methods of modern ultrasonography training employing high-end information technology tools. It spans from the most critical moments, examination, to image-based training methods. Hardware and software based solutions are introduced along their current limitations. A comprehensive overview is provided about the most popular ultrasound simulators based on a common set of criteria, including their basic features, simulation methods, training concept and the supported scanning protocols. Tutors shall be able to make better informed decisions based on the enlisted characteristics of the various systems. The principles of simulation methods and techniques are also discussed in details along with the challenges of the field.

Keywords: medical imaging; ultrasound diagnostics; ultrasound simulation & training

Abstract: A maximum power point tracking (MPPT) system, for a very high-efficiency photovoltaic array applied to a solar-powered vehicle, was studied in this work. Photovoltaic energy is a promising alternative energy; however, its high initial cost, it is essential to improve the energy conversion efficiency. Regarding a particular incident solar insolation and temperature, there is a specific voltage at which maximum power may be harvested (Maximum power point, MPP). The Maximum Power Point is therefore achieved at a specific voltage that depends on insolation and temperature. A proper maximum power point tracking system is particularly important for solar-powered vehicles relating to the rapid change of insolation due to the dynamic motion of the vehicle. In this paper, the emphasis is on the potential of energy conversion improvement of a PV system, associated with a moving vehicle via the use of a fuzzy based maximum power point tracking algorithm.

Keywords: Maximum Power Point Tracking (MPPT); the fuzzy controller; Photovoltaic Dynamic Tracking (PVT); solar electric vehicle

Abstract: The aim of this research was to develop a robust motor controller for the Szabad(ka)-II hexapod robot. A Fuzzy-PI controller that utilized a lookup table was chosen because of its reported promising performance and its ability to be embedded in the microcontrollers of the robot. The variables of the controller were defined by a particle swarm optimization method to minimize the five quality objectives related to the walking of the robot. The preferences of the five objectives were successfully expressed by a biased-weighted geometric mean utility function. The resulting optimal solutions were significantly altered by changing the bias and exponential weights of preferences. Therefore, we checked the robustness of the solution against the controller’s variables as a secondary objective.

Keywords: multi-scenario; multi-objective optimization; fuzzy control; robot dynamic simulation

Abstract: The paper presents the results of our research in the field of combining process algebra and Petri nets. To provide better support for design and analysis of larger-scale systems by means of abstraction mechanism, the method itself and the tools allowing its practical application have been enhanced significantly. The theoretical aspects and implementation of enhancements are discussed in detail. Careful testing, along with the process of implementing the new functionality into one of the involved tools, helped us to disclose its certain hidden imperfections, which are subsequently addressed.

Keywords: process algebra; Petri nets; formal methods integration; abstraction

Abstract: The objective of this paper is to summarize the factual results of eight year application of the SOL safety event analysis methodology for the period of 2007-2015 in a nuclear power plant in Hungary. After putting the SOL analyses into a wider context, 531 particular contributing factors were identified and classified into the 20 broad standard SOL contributing factor categories. It turned out that a 28 item "toplist" of the particular contributing factors altogether contains 236 out of the total of 531 - corresponding to about 44% - and their highest frequency socio-technical system component category was the "Organization" (118.50%), closely followed by the "Individual" (98.41%). Based on the identified contributing factors and their relative weights, the corrective measures taken could prevent these - or similar other - events from recurring.

Keywords: SOL; safety event analysis methodology; nuclear power plant

Abstract: The object of the paper is a priori energy cost estimation for the motion work performed by electric drive systems. We tested an original method for finding the efficiency of motion along a pre-specified path. Two mathematical models: the classic point-to-point trajectory planning and the interpolation model for the efficiency of the energy conversion process provide the data for energy cost estimation. First, the interpolation model was built using the electric drive actuator's data specifications. These data are the torque, speed, and efficiency for scattered steady-state operation points. The interpolation model builds the efficiency surface vs. torque and speed, which passes through all specification points of the actuator. If the required trajectory is superposed on the efficiency surface, we can find the incremental values of the efficiency which correspond to trajectories speed and torque. These quantities are necessary and sufficient for energy cost estimation of the motion along the desired trajectory. The a priori calculation of energy costs for electromechanical motion processes is an important means of preventing the energy wastage by adopting the minimum cost trajectory based on execution time, command law and load torque.

Keywords: Electromechanical servo system; trajectories planning; minimum time and minimum RMS torque control; scattered points interpolation; interpolation model; energy efficiency of the motion