Web accessibility investigation of Slovenian municipalities’ websites before and after the adoption of European Standard EN 301 549

Universal Access in the Information Society - Digitalization and technological innovations provide many benefits for citizens worldwide, increasing the quality of life in several ways, including by...     

Hexaferrite/Polyester Composite Coatings for Electromagnetic-Wave Absorbers

Composite coatings, consisting of a ceramic barium hexaferrite and polyester, were manufactured by atmospheric plasma spraying. The crystalline structure of the barium hexaferrite was preserved during the spraying process while the polyester first (partly) melted and then resolidified. The high magnetic losses of the barium hexaferrite at mm-waves were coupled to the dielectric losses of the polyester in the composite coating and the superior electromagnetic absorption of the composite coating with respect to the pure materials was determined.     

The low-temperature formation of barium hexaferrites

We have investigated the formation of barium hexaferrites with the compositions BaFe₁₂O₁₉ and Ba₂Co₂Fe₁₂O₂₂ using precipitation in ethanol. A mechanism for the formation was proposed, based on the results of thermal analysis, X-ray powder diffraction, electron microscopy and the magnetic properties of powders prepared under various precipitation and calcination conditions. The influence of the precipitation conditions on the formation mechanism and the reaction rate was studied. By replacing the water with ethanol the formation temperatures of both compounds were decreased to well below 1000 °C, and the homogeneity of their microstructures was improved. As a result, homogeneous and dense ceramics were obtained at 1200 °C. Precipitation from ethanol solutions proved to be a simple method for the low-temperature preparation of barium hexaferrites.     

Coulomb Blockade Peak Statistics Influenced by Background Charge Configuration

Statistics of Coulomb blockade oscillations in metallic singleelectron transistors are investigated. We observe stronglynon-Gaussian distributions of nearest-neighbor conductancepeak spacings. The fluctuations of peak position are found tobe reproducible as a function of gate voltage, with ahysteresis when sweeping the voltage up and down. Our resultsare explained in terms of gate potential dependentbistabilities in the background charge configuration. Weemphasize the importance of carefully taking into account theenvironmental charge fluctuations in high sensitivityelectrometric SET experiments, like such on single particlelevel statistics in semiconductor quantum dots.     

Integrated Genetic Programming and Genetic Algorithm Approach to Predict Surface Roughness

In this article we propose a new integrated genetic programming and genetic algorithm approach to predict surface roughness in end-milling. Four independent variables, spindle speed, feed rate, depth of cut, and vibrations, were measured. Those variables influence the dependent variable (i.e., surface roughness). On the basis of training data set, different models for surface roughness were developed by genetic programming. The floating-point constants of the best model were additionally optimized by a genetic algorithm. Accuracy of the model was proved on the testing data set. By using the proposed approach, more accurate prediction of surface roughness was reached than if only modeling by genetic programming had been carried out. It was also established that the surface roughness is most influenced by the feed rate, whereas the vibrations increase the prediction accuracy.     

Modeling of Total Decarburization of Spring Steel with Genetic Programming

Store Steel Ltd. is one of the biggest spring steel producers in Europe. Spring steel should have proper chemical composition and microstructure and should be without surface defects. Decarburization—that is, reduction of carbon content—also influences spring steel surface quality. During regular production, the data regarding rolled spring steel bars (width, reduction rate, chemical composition, and total decarburization) and the heating furnace for heating billets before rolling (heating temperature, time, and oxygen content) were monitored. On the basis of the monitored data, a mathematical model for the total decarburization depth was developed by genetic programming and linear regression. The average relative deviations from experimental data for the genetic programming developed and linear regression models are 18.186% and 22.999%, respectively. According to the developed models, the heating temperature was lowered, and, consequently, 24.29% lower total decarburization (t-test, p < 0.05) and also 20.65% lower heating furnace natural gas consumption was achieved (t-test, p < 0.05).     

Comparative study of European tunnel emergency-stop-area-wall protection measures

Due to the increasing number of traffic accidents involving the collisions of vehicles with the emergency-stop-area head walls in tunnels, a comparative numerical analysis in accordance with the EN 1317 standard has been performed in order to assess the quality of the available protective safety barriers. Based on the simulation results, the values of the relevant injury criteria – the acceleration severity index (ASI), the theoretical head impact velocity (THIV) and the post-impact head deceleration (PHD) – were computed for several collision scenarios involving two different passenger vehicles colliding with two different safety barriers in various ways. The results show that due to the geometrical restrictions in the tunnel's emergency stop area none of the barriers can provide total protection for the occupants of the vehicle in the event of a collision. The installation of a steel-sheet-tube crash cushion was, however, found to provide the best possible protection within the given limitations. The results of the analysis were the basis for selecting a safety-barrier design for existing tunnel installations and for the proposed changes in regulations governing the geometry of the tunnel's emergency stop area.     

Smartphone with Augmented Gateway Functionality as Opportunistic WSN Gateway Device

Sensors and actuators are being increasingly deployed for monitoring and controlling different phenomena and processes in a stand-alone manner or attached to sensor nodes with communication capabilities as part of larger wireless sensor networks (WSN). In addition to the protocols for communication within the WSN, sensor nodes may also provide the gateway functionality towards other networks and/or support communication with other external devices. These devices either represent additional gateways for exposing data and metadata to external networks, or serve as connection points to WSN for instance for the on-site calibration and maintenance. Smartphones as advanced mobile terminals appear particularly suitable for such role. This paper investigates the role a smartphone augmented with WSN gateway functionality can play in WSN with respect to regular dedicated sensor and gateway nodes. As a practical example we show the implementation of a gateway augmented smartphone using a Samsung i8910 phone and a VESNA sensor node connected via Bluetooth. The role of a gateway augmented smartphone is to interface between WSN, which is using a proprietary networking protocol, and the mobile network. The data obtained from WSN can be enriched using smartphone’s embedded sensors before being sent to the remote server. We demonstrate this on an example of geo-tagging the collected data from WSN with the smartphone’s Global Positioning System-based location data.     

Thermal Stability of (Co,Cu)Z-Hexaferrite and Its Compatibility with Ag at 900°C

Z-type hexaferrite with the composition Ba₃Co_1.4Cu_0.6Fe₂₄O₄₁ was studied as a candidate material for low-temperature cofiring technology. The samples were prepared by solid-state reaction at 1250°C and sintered and cosintered with Ag at 900°C. Bi₂O₃ was used as a sintering additive, which was necessary for the sintering at 900°C. The samples were characterized with X-ray diffraction, electron microscopy, and energy-dispersive spectroscopic analysis. The compatibility study of (Co,Cu)Z-hexaferrite with Ag revealed the degradation of the Z-hexaferrite. However, the present study shows that the (Co,Cu)Z-hexaferrite was compatible with Ag and that the degradation was caused by the thermal instability of (Co,Cu)Z-hexaferrite. The effect of the observed changes in phase composition on the permittivity and permeability of the samples was measured at 10⁶–10⁹ Hz.     

Initial Morphology and Grain Growth in Donor-Doped Barium Titanate

The influence of the initial grain morphology on the anomalous grain growth in donor-doped barium titanate has been studied. The results show that powders with aspherically shaped grains exhibit a much lower critical donor-dopant concentration, inhibiting anomalous grain growth during sintering, than powders with equisized spherically shaped grains and a similar, or even a lower, initial specific surface area.