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Abstract: Due to bridges’ critical role in transportation networks, the assessment and maintenance of existing bridges have become a priority. Prestressed concrete bridges constitute a significant portion of Europe’s transportation network, yet many no longer meet today’s technical requirements. This is primarily due to two factors: (i) the unforeseen increase in heavy goods traffic, and (ii) insufficient experience with early reinforced and prestressed concrete construction methods, coupled with inadequate regulations, which resulted in design weaknesses and structural deficiencies. One critical failure mechanism, identified when recalculating existing bridges based on updated guidelines, is insufficient shear load-bearing capacity, which has prompted the premature demolition of numerous bridges. A thorough understanding and rigorous monitoring of shear behavior is essential since neglecting this problem could lead to notable consequences, especially for aging infrastructure. In this paper, a distributed fiber optic sensor (DFOS) based monitoring system, inspired by shear detection concepts, is tested. A decommissioned prestressed concrete bridge girder was equipped with a DFOS grid, allowing for detailed monitoring of crack width, location, and shape. Preliminary test results confirm the successful installation and early detection of cracks, highlighting the system’s potential to identify microcrack formation, monitor crack growth, and support maintenance strategies.
Keywords: structural health monitoring, distributed fiber optic sensors, microcracking, crack growths, load testing, prestressed concrete
Published in DiRROS: 27.01.2026; Views: 178; Downloads: 91
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Keywords: fast silicon sensors, charge multiplication
Published in DiRROS: 26.01.2026; Views: 123; Downloads: 76
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Abstract: Electrochemical signals are traditionally interpreted in the time domain, where overlapping faradaic and non-faradaic currents, noise, and drift obscure frequency-dependent behaviour. This study introduces a frequency-domain framework that complements time-domain analysis by decomposing voltammetric signals into their harmonic components through Fourier methods. AC voltammetry provides experimental evidence of how increasing excitation frequency progressively suppresses faradaic clarity, while a modified Randles equivalent circuit model explains this response through the interplay of charge-transfer, diffusion, and double-layer charging processes. Fourier series analysis of canonical voltammetric techniques, including linear sweep, cyclic, differential pulse, and square wave voltammetry, shows that waveform geometry uniquely defines harmonic structure. Fast Fourier transform analysis of practical data reveals artefacts introduced by finite sampling, binning, and spectral leakage. These effects highlight the need for conceptual awareness when interpreting experimental spectra. Quantitative spectral descriptors such as the centroid, bandwidth, flatness, and low-frequency power fraction link waveform design directly to faradaic visibility and measurement clarity. Frequency-domain analysis therefore establishes that electrochemical measurement is inherently frequency-structured. By combining experimental data, equivalent circuit modelling and spectral metrics within a single framework, this approach provides a general route to optimise waveform parameters, reduce capacitive interference, and improve interpretability across electrochemical techniques. Viewed more broadly, this perspective reframes the process of the measurement itself, showing that time-domain signals are projections of an underlying spectral reality.
Keywords: frequency domain, spectral decomposition, electrochemical sensors, benzenediols
Published in DiRROS: 22.12.2025; Views: 716; Downloads: 128
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Abstract: Background: Freezing of gait (FoG) is one of the most debilitating motor symptoms in Parkinson’s disease (PD). It often leads to falls and reduces quality of life due to the risk of injury and loss of independence. Several types of wearable sensors have emerged as promising tools for the detection of FoG in clinical and real-life settings. Objective: The main objective of this systematic review was to critically evaluate the current usability of wearable sensor technologies for FoG detection in PD patients. The focus of the study is on sensor types, sensor combinations, placement on the body and the applications of such detection systems in a naturalistic environment. Methods: PubMed, IEEE Explore and ACM digital library were searched using a search string of Boolean operators that yielded 328 results, which were screened by title and abstract. After the screening process, 43 articles were included in the review. In addition to the year of publication, authorship and demographic data, sensor types and combinations, sensor locations, ON/OFF medication states of patients, gait tasks, performance metrics and algorithms used to process the data were extracted and analyzed. Results: The number of patients in the reviewed studies ranged from a single PD patient to 205 PD patients, and just over 65% of studies have solely focused on FoG + PD patients. The accelerometer was identified as the most frequently utilized wearable sensor, appearing in more than 90% of studies, often in combination with gyroscopes (25.5%) or gyroscopes and magnetometers (20.9%). The best overall sensor configuration reported was the accelerometer and gyroscope setup, achieving nearly 100% sensitivity and specificity for FoG detection. The most common sensor placement sites on the body were the waist, ankles, shanks and feet, but the current literature lacks the overall standardization of optimum sensor locations. Real-life context for FoG detection was the focus of only nine studies that reported promising results but much less consistent performance due to increased signal noise and unexpected patient activity. Conclusions: Current accelerometer-based FoG detection systems along with adaptive machine learning algorithms can reliably and consistently detect FoG in PD patients in controlled laboratory environments. The transition of detection systems towards a natural environment, however, remains a challenge to be explored. The development of standardized sensor placement guidelines along with robust and adaptive FoG detection systems that can maintain accuracy in a real-life environment would significantly improve the usefulness of these systems.
Keywords: Parkinson’s disease, wearable sensors, freezing of gait, symptoms
Published in DiRROS: 24.11.2025; Views: 656; Downloads: 178
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Abstract: : An integrated miniature electrochemical sensor (ES) that offers rapid, sensitive, and selective detection of chemical and biological contaminants in a variety of samples requires temperature control to work accurately. To address this, one approach is to locate temperature sensor (TS) next to the ES components. However, this integration poses a challenge as different firing processes are required for the sensor components and the TS. Commercially available thick-film materials for the realisation of TS are designed for screen printing on alumina and firing in air at 850 °C for 10 minutes. However, a key component of an ES, a carbon-based working electrode, must be fired in an oxygen-lean atmosphere. In this study, we investigated the influence of the firing atmosphere, i.e., air and argon, on the characteristics of thick-film resistors, including thickness, roughness, phase composition, resistivity, and temperature dependence. For the study, we used two commercially available thick-film pastes, NTC2114 and NTC2113, as TS with nominal sheet resistivities of 10 kΩ/sq and 1 kΩ/sq at 25 °C, respectively. Using X-ray powder diffraction analyses, we detected RuO2 and spinel phases in the samples heated at 850 °C in air. However, when the samples were fired in argon, we detect metallic ruthenium and alloys. As a result of these changes, the resistivity of the NTC2114 and NTC2113 increased significantly. However, despite these changes, the relative resistance and the coefficient of temperature sensitivity did not vary significantly, indicating the suitability of these materials as TS. These findings have important implications for the future integration of TS into various screen-printed ES systems, fostering the design and development of systems with enhanced accuracy and reliability in temperature measurements.
Keywords: NTC, thick film, screen printing, temperature sensors
Published in DiRROS: 23.10.2025; Views: 358; Downloads: 163
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