Search Results (6)

Railway signalling systems must ensure the safe movement of trains and the reliability of the operation of their components is of utmost importance. One of the main components is the interlocking devices, which provide secure, safe and reliable interaction between points and signals in the controlled railway station area, and the safe movement of trains in this area depends on their proper functioning. In this article, the failures of the signalling devices in the Bulgarian railways over a three-year period (2020–2022) are analysed and processed according to a developed methodology. First, a statistical assessment of device failures is performed, comparing the number and duration of failures of different types of equipment, and calculating proportional ratios. Second, a reliability analysis is carried out and the reliability indicators are determined—mean time between failures MTBF, intensity of failure flow, availability and unavailability coefficients. The obtained results clearly demonstrate the need for determination of the complex reliability indicators. They give the clearest assessment of the state of the devices. If only a statistical assessment of failures and their duration is made or if only simple reliability indicators are calculated, erroneous conclusions can be drawn regarding maintenance and the need for modernization. Full article

The presented manuscript demonstrates the effect of the thickness of a zinc alloy sublayer on the corrosion resistance and stability of three types of bi-layer systems composed of Co- or Ni-modified zinc coatings (both as sublayers) and a top sol–gel ZrO₂ film in a 5% NaCl solution. In order to obtain more detailed information, the alloy sublayers were electrodeposited with three different thicknesses (1, 5 and 10 µm, respectively) on a low-carbon steel substrate. Three consecutive dip-coated ZrO₂ sol–gel layers were deposited thereafter on the individual zinc alloy sublayers. For comparison, an ordinary electrodeposited zinc coating was obtained and investigated. The aim of this study was to evaluate the effect of the thickness of the zinc-based sublayer on the protective characteristics of the bi-layer systems. The surface morphology features and the phase composition of the latter systems were examined using scanning electron microscopy (SEM), atomic force microscopy (AFM), water contact angle (WCA) measurements and X-ray diffraction (XRD) analyses. The corrosion stability was evaluated by means of potentiodynamic polarization (PDP) curves and polarization resistance (Rp) measurements. The zirconia finish layers possessed an amorphous, dense and hydrophobic nature, while the sublayers were multicrystalline. The results confirmed the increased corrosion resistance of the protective system, which contains electrodeposited sublayer of Zn-Co alloy with a 10 µm thickness in a corrosive test medium. Full article

This study aimed to present the differences in the corrosion properties and protective ability of two bi-layer systems obtained on low-carbon steel in a model corrosive medium of 5% NaCl solution. These newly developed systems consist of Zn-Co (3 wt.%) or Zn-Ni (10 wt.%) alloy coatings as under-layers and a very thin TiO₂ sol-gel film as a top-layer. Scanning electron microscopy (SEM) is used for characterization of the surface morphology of the samples indicating that some quantitative differences appear as a result of the different composition of both zinc alloys. Surface topography is investigated by means of atomic force microscopy (AFM), and the hydrophobic properties are studied by contact angle (CA) measurements. These investigations demonstrate that both sample types possess grain nanometric surface morphology and that the contact angle decreases very slightly. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are used for characterization of the chemical composition and electronic structure of the samples. The roughness R_q of the Zn-Ni/TiO₂ is 49.5 nm, while for Zn-Co/TiO₂, the R_q value is 53.4 nm. The water contact angels are 93.2 and 95.5 for the Zn-Ni/TiO₂ and Zn-Co/TiO₂ systems, respectively. These investigations also show that the co-deposition of Zn and Ni forms a coating consisting entirely of Ni₂Zn₁₁, while the other alloy contains Zn, Co and the intermetallic compound CoZn₁₃. The corrosion resistance and protective ability are estimated by potentiodynamic polarization (PDP) curves, as well as polarization resistance (R_p) measurements for a prolonged test period (35 days). The results obtained are compared with the corrosion characteristics of ordinary zinc coating with an equal thickness. The experimental data presents the positive influence of the newly developed systems on the enhanced protective properties of low-carbon steel in a test environment causing a localized corrosion—lower corrosion current density of about one magnitude of order (~10⁻⁶ A.cm⁻² for both systems and ~10⁻⁵ A.cm⁻² for Zn) and an enhanced protective ability after 35 days (~10,000–17,000 ohms for the systems and ~900 ohms for Zn). Full article

Inflammation of the upper respiratory tract in patients with allergic rhinitis (AR) may contribute to lower respiratory airways’ inflammation. T-helper 17 (Th17) cells and related cytokines are also involved in the immunological mechanism of AR along with the classical Th2 cells. It is hypothesized that upon Th2 pressure, the inflammatory response in the lungs may lead to Th17-induced neutrophilic inflammation. However, the findings for interleukin-17 (IL-17) are bidirectional. Furthermore, the role of Th17 cells and their counterpart—T regulatory cells—remains unclear in AR patients. It was also shown that a regulator of inflammation might be the individual circulating specific non-coding microRNAs (miRNAs), which were distinctively expressed in AR and bronchial asthma (BA) patients. However, although several circulating miRNAs have been related to upper and lower respiratory tract diseases, their function and clinical value are far from being clarified. Still, they can serve as noninvasive biomarkers for diagnosing, characterizing, and providing therapeutic targets for anti-inflammatory treatment along with the confirmed contributors to the pathogenesis—Th17 cells and related cytokines. The narrow pathogenetic relationship between the nose and the bronchi, e.g., upper and lower respiratory tracts, confirms the concept of unified airway diseases. Thus, there is no doubt that AR and BA should be diagnosed, managed, and treated in an integrated manner. Full article

The present study’s objective is to focus on some developments in the field of statistical models of a complex system, like nanoparticles responses in the environmental media. An important problem that still needs to be studied and interpreted is the relations between physicochemical parameters of the nanoparticles like primary size, primary hydrophobic diameter, zeta potential, etc. with respective toxicity values. It holds true especially for silver nanoparticle systems due to their known bactericidal effect and wide distribution in practice. The present study deals with the data for physicochemical and toxicity parameters of 94 different silver nanoparticle systems in order to reveal specific relations between physicochemical properties and acute toxicity readings using multivariate statistical methods. Searching for these specific relationships between physicochemical parameters and toxicity responses is the novel element in the present study. This has focused our study toward developing a model that describes the relationship between physicochemical properties and toxicity of silver NPs based on a dataset gathered from the literature. It is shown that the systems studied could be divided into four patterns (clusters) of similarity depending not only on the physicochemical indicators related to particles size but also by their acute toxicity. The acute toxicity is strongly correlated to the zeta potential of the particles if the whole data set is considered. Full article

The present study deals with the assessment of pollution caused by a large industrial facility using multivariate statistical methods. The primary goal is to classify specific pollution sources and to apportion their involvement in the formation of the total concentration of the chemical parameters being monitored. This aim is accomplished by intelligent data analysis based on cluster analysis, principal component analysis and principal component regression analysis. Five latent factors are found to explain over 80% of the total variance of the system being conditionally named “organic”, “non-ferrous smelter”, “acidic”, “secondary anthropogenic contribution” and “natural” factor. The apportionment models designate the contribution of the identified sources quantitatively and help in the interpretation of risk assessment and management actions. Since the study takes into account pollution uptake from soil to a cabbage plant, the data interpretation could help in introducing biomonitoring aspects of the assessment. The chemometric expertise helps in revealing hidden relationships between the objects and the variables involved to achieve a better understanding of specific pollution events in the soil of a severely industrially impacted region. Full article