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The amount of freight transported by rail and the number of passengers are increasing year by year. Any disruption to the passenger or freight transport stream can generate both financial and human losses. Such a disruption can be caused by the rail infrastructure being in poor condition. For this reason, the state of the infrastructure should be monitored periodically. One of the important elements of railroad infrastructure is the ballast. Its condition has a significant impact on the safety of rail traffic. The unevenness of the ballast surface is one of the indicators of its condition. For this reason, a regulation was introduced by Polish railway lines specifying the maximum threshold of ballast unevenness. This article presents an algorithm that allows for the detection of irregularities in the ballast. These irregularities are determined relative to the surface of the sleepers. The images used by the algorithm were captured by a laser triangulation system placed on a rail inspection vehicle managed by the Polish railway lines. The proposed solution has the following elements of novelty: (a) it presents a simple criterion for evaluating the condition of the ballast based on the measurement of its unevenness in relation to the level of the sleeper; (b) it treats ballast irregularity detection as an instance segmentation process and it compares two segmentation algorithms, Mask R-CNN and YOLACT, in terms of their application to ballast irregularity detection; and (c) it uses segmentation-related metrics—mAP (Mean Average Precision), IoU (Intersection over Union) and Pixel Accuracy—to evaluate the quality of the detection of ballast irregularity.

Persistent homology is an effective topological data analysis tool to quantify the structural and morphological features of soft materials, but so far it has not been used to characterise the dynamical behaviour of complex soft matter systems. Here, we introduce structural heterogeneity, a topological characteristic for semi-ordered materials that captures their degree of organisation at a mesoscopic level and tracks their time-evolution, ultimately detecting the order-disorder transition at the microscopic scale. We show that structural heterogeneity tracks structural changes in a liquid crystal nanocomposite, reveals the effect of confined geometry on the nematic-isotropic and isotropic-nematic phase transitions, and uncovers physical differences between these two processes. The system used in this work is representative of a class of composite nanomaterials, partially ordered and with complex structural and physical behaviour, where their precise characterisation poses significant challenges. Our developed analytic framework can provide both a qualitative and quantitative characterisation of the dynamical behaviour of a wide range of semi-ordered soft matter systems. Topological data analysis is an important framework for quantifying the structural and morphological features of soft materials. Here, structural heterogeneity is introduced as a quantitative measure of non-equilibrium mesoscopic order in soft matter and used to track the time-evolution of liquid crystal phase transitions.

Compliant mechanisms have gained an increasing interest in recent years, especially in relation to the possibility of using 3D printers for their production. These mechanisms typically find applications in precise positioning systems of building robotic devices or in sensing where they can be used to characterize displacement. Three-dimensional printing with PLA materials allows fiber optic-based sensors to be incorporated into the structures of properly designed compliant mechanisms. Therefore, in this paper, an innovative technology is described, of a Fiber Bragg Grating (FBG) sensor embedded in a measuring head which was then inserted into a specially designed mechanical transmission element. The shape of this element is based on clippers that allow to freely modify the amplification of displacement amplitude so that the FBG sensor always works in the most optimal regime without any need to modify its external dimensions. Flexural sensitivity of the replaceable measuring head equal to 1.26 (mε/mm) can be adapted to the needs of the flexure design.

The paper presents comparative laboratory investigations of tension fastener models that attach rails to concrete sleepers. The aim of the paper was to assess the influence of geometric nonconformity of the actual industrial product that meets the PKP Polskie Linie Kolejowe S.A. requirements on the operation of a tension-fastening clamp under stress. Due to the cost and limited possibility of research of the actual industrial product, an additional objective of the research was to validate the usefulness of it in the comparative assessment of the models. In the research, the authors used models of tension fastening clamps manufactured in incremental engineering technology (3D print) on scale 1:2. The properties of the fastening clamps (in their nominal shape) were compared (described in the PKP Polskie Linie Kolejowe S.A. documentation) with the fastening clamps of the actual shape. In the investigation, the authors have confirmed the negative influence of the non-conformance of the shape of the actual fastening clamps with the nominal ones.

Utilization of natural processes can reduce the complexity and production cost of any device by limiting the necessary steps in the production scheme, especially when it comes to fibers with periodic changes in refractive index. One such process is the nematic–isotropic phase separation of liquid crystal-based composite confined in 1D space. In this paper, we analyze the behavior of polymer-stabilized liquid crystal-based self-assembled periodic structures in an external electric field. We performed a detailed analysis regarding the reorientation of liquid crystal molecules under two orthogonal directions of the external electric field applied to the examined sample. It was demonstrated that the period of the polymerized structure remains constant until full reorientation, as the electric field induces the formation of new periodic defects in LC orientation. Consequently, the structure’s effective birefringence changes quite drastically, and this observed change depends on the direction of the electric field vector. The obtained results seem promising when it comes to application of the proposed periodic structures as voltage or electric field sensors operating as long-period fiber gratings or fiber Bragg gratings for the visible or near-infrared spectral regions.

Aim: This article presents an identification and analysis of the hazards associated with the operation of lithium-ion technology, the range of applications, an overview of hazardous incidents domestically and also internationally, the brief history of lithium-ion batteries, as well as recommendations on the use and storage of batteries published not only by domestic but also foreign fire and occupational safety organizations. Introduction: The increased mobility of people doing their work with computers has created the need to produce portable devices that require concentrating as much energy as possible in a limited enclosure volume. These devices accompany the user in everyday life, during travel and also in a variety of work. In order to meet these criteria, it was necessary to solve these problems, first of all, the problem of power supply, which would allow to use the electricity stored by them in a long-lasting but also very efficient way. However, modern solutions bring a number of new risks that are not obvious at first glance and require detailed analysis. Project and methods: Based on a critical analysis of the literature, the authors presented the advantages and disadvantages of cells used in smartphones, laptops, portable power tools used in households across the globe and even electric cars. The development of lithium-ion battery technology and the expansion of their range of applications makes it necessary to develop solutions to enhance safety during their use, together with procedures to prevent possible explosions and fires, allowing effective life and health protection of users, as well as safeguarding all property and the environment. Methodology: Opierając się na krytycznej analizie literatury, autorzy przedstawili zalety i wady ogniw wykorzystywanych w smartfonach, laptopach, przenośnych elektronarzędziach, a nawet samochodach elektrycznych. Rozwój technologii produkcji akumulatorów litowo-jonowych oraz rozszerzenie zakresu ich zastosowania sprawia, że konieczne jest opracowanie rozwiązań zwiększających bezpieczeństwo podczas ich użytkowania oraz procedur zapobiegania ewentualnym wybuchom i pożarom, pozwalających na skuteczną ochronę życia oraz zdrowia użytkowników, a także zabezpieczenie wszelkiego mienia i środowiska. Conclusions: In order to prevent fires spreading, it is necessary to understand the mechanisms that lead to ignition and possible explosions of cells and batteries. From the point of view of preventing such failures and fires, it is important to recognize the response of burning batteries to various types of fire extinguishing agents and preventive measures. Continued research in this area can contribute to the evolution of more sophisticated and advanced safety technologies and the development of regulatory standards that in the future will guarantee the effective control of lithium-ion battery fires directly linked to their storage, use at high quantities, and the correct storage of waste (in the form of damaged and depleted batteries). Keywords: lithium-ion batteries, fire hazard, environmental protection, environmental pollution, toxic products of combustion

Polymer–matrix composites degrade under the influence of UV radiation in the range of the 290–400 nm band. The degradation of polymer–matrix composites exposed to UV radiation is characterized by extensive aging of the epoxy matrix, resulting in deterioration of their mechanical properties. Glass fibers/epoxy resin composites were made by an out-of-autoclave method whereas a fiber optic sensor was placed between different layers of laminates. In our work, we used a fiber Bragg grating sensor covered with graphene oxide and embedded in a polymer matrix composite to monitor UV radiation intensity. Measurements of UV radiation may allow monitoring the aging process of individual components of the polymer composite. In order to estimate the number of microcracks of epoxy resin, microstructure observations were carried out using a scanning electron microscope.

Cel: Celem artykułu jest przedstawienie aktualnego stanu wiedzy w zakresie możliwości tłumienia lub skutecznego ugaszenia pożarów pojazdów elektrycznych. Z uwagi na wzrost popularności środków transportu zasilanych z akumulatorów elektrycznych, rozpoznawalna staje się problematyka pojawiających się pożarów i ich skutków. Z uwagi na możliwy gwałtowny proces przebiegu spalania akumulatorów litowo-jonowych (dalej akumulatory Li-Ion), wystąpienie pożaru w pojeździe może doprowadzić do szerokiego spektrum uszkodzeń mienia. Od co najmniej dekady prowadzone są intensywne działania ukierunkowane na wypracowanie właściwych metod pozwalających strażakom zmierzyć się z problemem pożarów pojazdów elektrycznych. Działania te ukierunkowano m.in. na nowe techniki gaszenia/tłumienia pożaru, innowacyjne środki gaśnicze i sposoby ich aplikacji. Wprowadzenie: Ratownicy coraz częściej spotykają się z pożarami układów gromadzenia energii elektrycznej wykonanych w technologii Li-Ion, w tym stosowanych w pojazdach elektrycznych. Biorąc pod uwagę obecne, światowe trendy zmiany sposobu zasilania pojazdów z paliw pochodzących z kopalin na energię elektryczną, należy spodziewać się intensyfikacji pojawiania się takich zdarzeń. Autorzy systematyzują zagadnienie poprzez analizę literaturową w zakresie pożarów akumulatorów Li-Ion jako krytycznego elementu mogącego zapoczątkowywać pożar. Analizie także poddano przyjęte i praktykowane metody gaszenia/tłumienia pożaru oraz wykorzystane środki gaśnicze. Publikacja może stanowić element pomocny w doborze najbardziej optymalnej metody ugaszenia pożaru zespołu gromadzenia energii elektrycznej w pojeździe. Metodologia: Przeglądu obecnego stanu wiedzy dokonano na podstawie publikacji dotyczących charakterystyki pożarowej akumulatorów Li-Ion, a także prac oraz projektów naukowo-badawczych z zakresu metod gaszenia i efektywności różnych środków gaśniczych. Ponadto analizie poddano procedury stosowane przez służby ratownicze oraz wybrane zdarzenia rzeczywiste. Wnioski: Pożary akumulatorów Li-Ion to stosunkowo nowe i narastające zjawisko. Pożary pojazdów w pełni lub częściowo elektrycznych są znacznie trudniejsze do pełnego ugaszenia w porównaniu do pożarów pojazdów z silnikami spalinowymi. Jak dotąd nie opracowano skutecznej metody, która pozwoliłaby na ugaszenie pożaru w krótkim czasie. Działania w tym obszarze skupiają się na minimalizacji skutków. W dalszym ciągu istnieje potrzeba szukania nowych rozwiązań technicznych i taktycznych w celu optymalizacji procedur prowadzących do bardziej efektywnych działań służb przy tego rodzaju zdarzeniach.

This paper presents the possibility of applying a soft polymer coating by means of a layer-by-layer (LbL) technique to highly birefringent polymer optical fibers designed for laminating in composite materials. In contrast to optical fibers made of pure silica glass, polymer optical fibers are manufactured without a soft polymer coating. In typical sensor applications, the absence of a buffer coating is an advantage. However, highly birefringent polymer optical fibers laminated in a composite material are much more sensitive to temperature changes than polymer optical fibers in a free space as a result of the thermal expansion of the composite material. To prevent this, we have covered highly birefringent polymer optical fibers with a soft polymer coating of different thickness and measured the temperature sensitivity of each solution. The results obtained show that the undesired temperature sensitivity of the laminated optical fiber decreases as the thickness of the coating layer increases.

Aim: The aim of this article is to determine the characteristics of a pool fire, including the temperatures and thermal radiation densities caused by it. Mappings of pool fires occurring in actual emergency events were conducted by performing large-scale polygon tests. Project and methods: Experimental study of pool fire of technical ethanol was carried out on a specially built test stand in the training area of the Training Centre in Pionki of the Regional Headquarters of the State Fire Service in Warsaw. The pool fire test stand consisted of a test tray, with a test chamber with the diameter of 300 cm, founded on a reinforced concrete slab. Using a developed measurement system with data acquisition that included measurement sensors mounted at defined locations relative to the fire, temperatures and thermal radiation densities were measured at various distances/locations relative to the fire. Metrological data such as air temperature, atmospheric pressure, humidity, wind direction and speed were monitored and recorded using the weather station. The height of the fire flame was measured by comparing it to racks set up nearby with marked scales of specific lengths. Results: A polygon stand that was built to study pool fires, equipped with a temperature and thermal radiation density measuring system with measuring sensors distributed in defined locations, is discussed. A study of a pool fire resulting from the combustion of dehydrated, fully contaminated ethanol was conducted. The study measured temperatures, thermal radiation densities, and flame heights. The average and maximum values of temperatures and thermal radiation densities during the steady-state combustion stage (i.e., phase II of the fire) were determined. Conclusions: Based on the presented results of temperature and thermal radiation density measurements at various distances/locations relative to the pool fire site, there was a significant effect of wind direction and speed on these values. Higher temperature and heat radiation density were recorded at the sensors on the leeward side than on the windward side. As the wind speed decreased, there was an increase in the temperature values recorded on the thermocouples located above the centre of the bottom of the tray test chamber due to the flame, which, when not blown away, was allowed to rise vertically upward and fully sweep the temperature sensors. Keywords: pool fire, field tests, technical ethanol, temperature, thermal radiation Type of article: original scientific article