Acta IMEKO

Detection of induction motor faults by envelopes of higher current harmonics

Tue, 25 Aug 2026 00:00:00 +0000

Detection of broken rotor bars in induction motors based on sideband components near the fundamental stator current frequency often yields unreliable results under variable operating conditions due to masking effects and the dominant amplitude of the fundamental component. This study proposes a robust fault detection method which uses higher-order current harmonics, which demonstrate significantly reduced susceptibility to load variations and other masking phenomena. As principal contribution this study demonstrates that a convolutional neural network trained exclusively on data derived from a single operating condition achieves strong generalisation across a wide spectrum of unsteady operating regimes, spanning substantially different supply frequencies and load levels, with consistently high classification accuracy. Signal processing involves bandpass filtering around the fifth and seventh harmonic frequencies, envelope extraction via the Hilbert transform, continuous wavelet transform to generate time-frequency scalograms, and data augmentation through vertical shifts to simulate variations in defect-related frequency components under changing slip conditions. Scalograms corresponding to the fifth and seventh harmonics are treated as independent training samples, effectively expanding the dataset while leveraging physically redundant fault information. This single-point training paradigm directly addresses a critical industrial limitation, thereby enabling deployment of data-driven condition monitoring systems even under severe training data constraints.

Enhancing accelerometer calibration results by reporting interpolated calibration data

Ian Veldman, Anderson Maina, Henrik Volkers — Tue, 18 Aug 2026 00:00:00 +0000

This paper describes the implementation of interpolation methods (fitting curves) for reporting complex (magnitude and phase) accelerometer calibration measurements. The authors’ evaluation focused on two interpolation methods: polynomial fit and mathematical model description of a charge accelerometer. Charge accelerometers, such as the Brüel & Kjær model 8305 and the ENDEVCO model 2270, are the de facto laboratory standard accelerometers. NMIs have been maintaining sensitivity calibration data, with the associated uncertainty of measurement (UoM), on such devices for decades and reported publicly available comparison data using these accelerometers, which provide ample vetted data for curve-fitting technique investigations.

Assessment of innovation management systems in established innovative companies: A conceptual model based on ISO 56002:2019 standard

Felippe Vicencio Gomes , Maria Fatima Ludovico de Almeida — Tue, 18 Aug 2026 00:00:00 +0000

This study presents a comprehensive assessment model designed to facilitate organizational excellence in innovation management through a systematic evaluation of maturity levels vis-à-vis the ISO 56002:2019 standard clauses and items. The practical applicability of the model was validated through an empirical investigation conducted at Light SESA, a prominent organization in the Brazilian electricity sector. The methodological framework encompasses six interconnected phases: (i) an extensive literature review and documentary analysis of pertinent research domains; (ii) development of an analytical framework based on ISO 56002:2019 parameters; (iii) implementation of the Analytic Network Process (ANP) for weight attribution to dimensional and factorial components within the assessment structure; (iv) design and validation of a survey instrument targeting senior leadership and RD&I project managers to evaluate organizational maturity relative to ISO 56002:2019 requirements; (v) application of fuzzy logic principles for processing collective judgments, thereby mitigating assessment bias; and (vi) utilization of Importance-Performance Analysis (IPA) methodology to identify priority areas for innovation management system enhancement. The primary contribution of this research is a robust, empirically validated model for assessing innovation management system maturity in organizations seeking to enhance their innovative capabilities and performance metrics.

Self-assessment model for pharmaceutical companies based on Good Manufacturing Practices for pharmaceuticals in Brazil: a multicriteria approach

Alexandre Nunes, Maria Fatima Ludovico de Almeida, Daniel Lousada — Tue, 18 Aug 2026 00:00:00 +0000

This study presents a novel self-assessment model for evaluating organizational compliance capabilities within Brazilian pharmaceutical companies regarding the Resolution RDC 658/2022 requirements established by the National Health Surveillance Agency (Anvisa) aligned with the World Health Organization's Good Manufacturing Practices (GMP) for pharmaceutical products. The research methodology comprised a systematic literature review and documentary analysis spanning 2010-2023, followed by the development of an analytical framework integrating the Analytic Hierarchy Process (AHP) for weighting the regulatory requirements of the aforementioned Resolution. The model's empirical validation was conducted through implementation at a Brazilian pharmaceutical company, evaluating its organizational compliance capabilities vis-à-vis the RDC 658/2022 requirements. Importance-Performance Analysis (IPA) was subsequently employed to prioritize areas that require enhanced regulatory compliance. The primary contribution of this study is a comprehensive self-assessment framework that provides pharmaceutical companies with robust decision-making support for visa certification processes. Empirical validation demonstrated the model's effectiveness in identifying critical compliance gaps and prioritizing improvement initiatives. This methodological advancement strengthens the interface between health regulatory authorities and pharmaceutical companies, potentially enhancing the effectiveness of Brazil’s regulatory system

Multicriteria conceptual framework for maturity assessment of testing and calibration laboratories based on the ISO/IEC 17025: 2017 standard

David Correa , Maria Fatima Ludovico de Almeida — Tue, 18 Aug 2026 00:00:00 +0000

This study presents a novel multicriteria framework for assessing the maturity of testing and calibration laboratories in accordance with ISO/IEC 17025:2017 requirements. The research methodology comprised a systematic literature review spanning 2010–2023, followed by the development of an analytical framework integrating the Analytical Hierarchy Process (AHP) for weighting standard requirements and the Importance–Performance Analysis (IPA) for maturity assessment. The framework's empirical validation was conducted at the Brazilian Army Evaluation Center (CAEx) to evaluate laboratory compliance capabilities vis-à-vis the ISO/IEC 17025:2017 requirements regarding competence, impartiality, and operational consistency. The validation process involved senior laboratory managers and resulted in quantitative maturity assessments across standard requirements, enabling the identification of critical improvement areas and the development of targeted action plans for accreditation preparation. The primary contribution of this study is a comprehensive assessment framework that provides testing and calibration laboratories with robust decision-making support for accreditation processes. The empirical validation demonstrated the effectiveness of the framework in identifying critical compliance gaps and prioritizing improvement initiatives. This methodological advancement is a significant contribution to the field of laboratory quality management.

Theoretical analysis of the impact of normalizing composite quality indicator components on their extrema

Anatolyi Dolzhanskiy, Oksana Bondarenko, Oleh Brahynskyi — Fri, 18 Sep 2026 00:00:00 +0000

Quality assessment of complex objects commonly employs composite quality indicators constructed from weighted individual quality indicators and management tools. When these variables differ in units or ranges, normalization to dimensionless values in [0, 1] is required. This transformation yields an alternative quality model whose extremum characteristics may differ from those of the original non-normalized model. This issue has received limited attention in the literature. The aim of this study is to analyse the effect of parameter normalization on the extremum of a composite quality indicator. The analysis considers general quality models based on weighted arithmetic, harmonic, geometric, and quadratic mean aggregation functions, each evaluated with and without normalization of individual quality indicators. The results reveal that normalization affects both the location and type of the extremum, as well as the optimal values of quality management tools, for arithmetic, harmonic, and quadratic mean convolutions. Notably, for the weighted geometric mean, the optimal management tool value is independent of normalization, making this convolution particularly suitable for practical quality management. These findings provide a foundation for developing dedicated back-transformation methodologies to ensure accurate real-world application of results obtained from normalized quality models.

Development of an IoT-based network for urban environmental monitoring in a vulnerable area of Los Ríos, Santo Domingo, Dominican Republic

Fri, 28 Aug 2026 00:00:00 +0000

The aim of this research phase was to develop an environmental data collection tool specific for the context of Los Ríos–Santo Domingo, where vulnerable settlements coexist with other clusters of higher socioeconomic status. The design of such tool needed to address the social, legal, and climatic frameworks of its context, while also aiming at a reliable, energy efficient, and replicable architecture. The project hopes to encourage future information-based participatory planning aimed at improving safety and elevating the quality of life in the area. The workflow carried out during this phase included: area visits, document consultation, work on an urban footprint map, review of comparable projects, device development, and the strategic selection of the installation site. The project achieved the design and production of ten compact devices that contain seven sensors each, to register concentrations of important air contaminants, vibration, sound intensity, and specific atmospheric conditions. Devices were installed within the inner perimeter of a property in the proximity of vulnerable and non-vulnerable polygons to enable the observation of potential reading differences. Preliminary total averages obtained from a sample showed high concentrations of CO, NO₂ (according to guidelines from WHO), and PM₁ (following the 2024 paper “On the safe levels of micro-sized particles PM1.0 in ambient air” by Zaitseva, Kleyn, Chetverkina, Andrishunas, and Tsinker), alongside noise levels between 6.9 and 74.09 dB in most units and RH values below 40 %.

Circularly polarized vision system for attenuation of reflection and glare

Luigi Montalto, Daniele Rinaldi, Paolo Castellini, Nicola Paone — Tue, 15 Sep 2026 00:00:00 +0000

The paper presents the use of applying circular polarization in a vision system. It describes how reflections and glare are reduced when illuminating a reflecting surface with circularly polarized light and collecting scattered light through the same circular polarizer. Even if usage of linear polarizers in vision systems is common, the use of circularly polarized light offers advantages due to the simplicity of the setup, which is composed of a single polarizing plate, without any need for accurate angular alignment, enhancing the contrast without significant loss of illumination due to the absence of dark field regions. Reduction of glare reduces image saturation, therefore allowing for a better contrast in images acquired from highly reflective surfaces.

Loss of accuracy compensation in determining a vessel's location with a mixed distribution of position line measurement errors

Igor Burmaka, Bogdan Alieksieichuk, Olha Burenko, Iryna Zhuravska — Tue, 15 Sep 2026 00:00:00 +0000

The objective of the investigation is to improve the accuracy of a ship’s position, based on navigational measuring equipment. The errors introduced into this process by key types of onboard equipment, including the GPS receiver, marine radar, and sextant, are analyzed. The errors of the sensors from which the measurement results are transmitted to the radar (gyrocompass, log, echo, etc.) are also considered. A multi-stage sequence in calculating the total positioning error from various navigational sources is also taken into account. The method for cumulative error compensation using redundant lines of position (LOPs) is proposed. The required measure of redundancy is determined based on derived analytic dependencies. The results of numerical experiments and natural observations are presented, confirming the appropriateness of using the proposed method. The proposed method and its results demonstrate its potential to improve positioning accuracy and ensure safe navigation.

Comparative assessment of ISO/IEC Guide 98-3 and Monte Carlo methods for temperature sensor calibration: A simulation-based study

Wed, 16 Sep 2026 00:00:00 +0000

The evaluation of measurement uncertainty is a task in metrology, and remains challenging when measurement models show nonlinearity, or when input quantities follow non-Gaussian probability distributions. Although the ISO/IEC Guide 98-3 (GUM) is widely applied in calibration practice, studies have highlighted situations in which its underlying assumptions may no longer be satisfied. In response to these developments, this paper presents a simulation-based comparative analysis of the GUM framework and the Monte Carlo method recommended in GUM Supplement 1, with a specific focus on temperature sensor calibration. We analysed a set of calibration scenarios, covering linear and nonlinear models, symmetric and asymmetric input distributions, and limited sample sizes. The comparison addresses uncertainty estimates, coverage behaviour, and computational aspects, allowing the practical consequences of each method to be assessed under controlled conditions. The results indicate that while the GUM approach remains suitable for near-linear models with approximately Gaussian inputs, Monte Carlo simulation provides a more faithful representation of the output distribution when these conditions are not met. For readers and practitioners, this study offers methodological insight and practical guidance for selecting an appropriate uncertainty evaluation approach in contemporary temperature sensor calibration, consistent with recent advances reported in the metrological literature.

Three-dimensional inertial measurement unit-based analysis of wheelchair racing propulsion using a Sensor-in-Glove System

Kimitomo Taniguchi, Tatsuru Ibusuki, Koichi Kawabata — Tue, 22 Sep 2026 00:00:00 +0000

This study proposes the Sensor‑in‑Glove System (SIGS), a field‑deployable method for measuring wheelchair racing propulsion during outdoor sprinting. SIGS synchronises two inertial measurement units (IMUs)—one embedded in a 3D‑printed glove and one mounted on the wheel—to capture push cycle‑wise hand and wheel kinematics. As a proof‑of‑concept validation, six elite athletes performed maximal‑effort 100‑m sprints. SIGS recorded continuous motion data, achieving a displacement‑estimation error of 0.73 % over a 10‑m interval. Propulsion onset and hand release were objectively identified from IMU signals without visual inspection, enabling the push cycle to be divided into mechanically meaningful phases. Newly defined 3D acceleration‑vector metrics revealed individual push styles, and peak resultant acceleration showed strong correlations with wheelchair velocity (r = 0.82–0.95). Class‑wise comparisons demonstrated significant differences in peak acceleration (F = 10.52, p < 0.001), indicating that SIGS captures impairment‑specific push characteristics. As the first field‑based 3D acceleration‑vector analysis using a glove‑embedded IMU, this study shows that SIGS provides a practical and quantitative approach for evaluating propulsion mechanics, and offers opportunities for technique assessment and athlete‑specific performance analysis in wheelchair racing.

Dust detector for museum environment based on Raspberry Pi: A first improvement

Mariagrazia Leccisi, Giuseppe Schirripa Spagnolo, Fabio Leccese — Mon, 21 Sep 2026 00:00:00 +0000

This work shows the development of a low-cost, easy-to-install, scalable, and highly integrable system, suitable for real and extensive applications for dust detection in museum environments. To detect particles, the Raspberry Pi uses a high-definition camera module on which dust naturally settles. After the acquisition of the image, the platform elaborates directly the images, recognizing and clustering the particles using a self-made recognition software.

Time measurement and uncertainty in Galileo’s inclined plane: From water clocks to electronic timing

Mon, 21 Sep 2026 00:00:00 +0000

A reconstruction of Galileo Galilei’s experimental apparatus used to investigate the dynamics of motion along an inclined plane is presented. The study not only replicates the measurements of distance and motion described in Galileo’s manuscripts, but also emphasizes the central role of time measurement in the formulation of the laws governing uniformly accelerated motion. The experiment is first reproduced using historically plausible instruments, including a reconstructed water clock, in order to assess the feasibility and precision of time measurements available in the seventeenth century. In addition, a comparative analysis is performed using modern measurement techniques: an electronic timing system based on LED–phototransistor pairs has been developed to acquire transit times with millisecond resolution. The comparison between historical and modern methods allows a quantitative evaluation of measurement uncertainty, and highlights the metrological limitations and capabilities of early experimental practices, while offering a contemporary verification of Galileo’s law of motion.

Comparative evaluation of CNN and ViT architectures for the petrographic classification of Levantine ceramic micrographs

Mon, 21 Sep 2026 00:00:00 +0000

This study explores the application of artificial intelligence (AI) techniques for the classification of Levantine ceramic thin sections based on their petrographic fabrics. The Levant is a key archaeological region, particularly during the transition from the Late Chalcolithic to the Early Bronze Age, marked by urbanization, craft specialization, and expanding interregional exchange networks. Ceramic production therefore provides crucial evidence for understanding technological practices and cultural interactions. We apply two deep learning architectures, convolutional neural networks (CNNs) and vision transformers (ViTs), to a large and heterogeneous dataset of ceramic thin-section micrographs dating from the Uruk period through the Bronze and Iron Ages. The dataset includes samples from 14 archaeological sites across the Levant, representing 20 different petrographic fabrics. To evaluate model robustness and generalization, we performed additional experiments by excluding samples from selected sites using them as an unseen test domain, simulating a real-world classification scenario under domain shift and class imbalance. Model performance was evaluated using macro-, micro-, and weighted-F1 scores. To improve model transparency, visual explainable AI approaches, such as Guided Grad-CAM and transformer attention maps, are applied to identify the most informative features driving classification decisions. The results demonstrate high classification performance, reaching an accuracy of 88.44 % for ResNet18 and 90.52 % for DeiT-small. Visual explanations further indicate that the models rely on mineralogical and textural features consistent with petrographic criteria used by human experts, supporting the archaeological interpretability of the proposed approach.

Evaluation of Radon exhalation rate, natural radioactivity content, and radiological hazard for untreated and aged Viterbo tuff stone

Thu, 24 Sep 2026 00:00:00 +0000

This research investigates the radon exhalation rate, natural radionuclide content, and associated radiological hazard to human health linked to Viterbo tuff stone, a material of notable historical and architectural relevance. Particular attention was given to radon exhalation behavior by examining both untreated and accelerated aged (through a salt crystallization test) samples. Radon exhalation rates were quantified using the Closed Chamber Method (CCM) in combination with a Durridge RAD7 real-time continuous radon detector. The measured exhalation rates were subsequently employed in the Markkanen room model to estimate potential indoor radon concentrations.

In addition, the activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K were determined by means of high-purity germanium (HPGe) gamma-ray spectrometry. Radiological hazard was evaluated using several indices, including the absorbed gamma dose rate (D), the annual effective dose equivalent (AEDE), the activity concentration index (I), and the alpha index (I_α).

Noteworthy, the findings of this study provide a valuable basis for future research aimed at developing a systematic framework for assessing radon release from building materials. Such an approach is essential for supporting decision-making processes, as it enables the identification of buildings that may be particularly susceptible to radiological risks, and therefore require targeted mitigation and protection measures.

In-situ molecular investigation of ancient and restoration mortars from the theatre of Tindari (Sicily, Italy) by DRIFTS and µ-Raman spectroscopy

Sun, 20 Sep 2026 00:00:00 +0000

We report an in-situ multi-technique study combining Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and µ-Raman spectroscopy for the molecular characterization of five mortar areas from the theatre of Tindari (Sicily, Italy). The selected areas, chosen as representative case studies within a broader diagnostic campaign, include three ancient mortars attributed to the Roman transformation phase of the monument, and two modern conglomerate- and cement-based materials employed in restoration works. The ancient areas are located on the podium and on the intrados of the vault of the annular corridor encircling the orchestra, while the modern restoration mortars are located on the scaena. DRIFTS spectra provided information averaged over the superficial portion investigated, whereas µ-Raman spectroscopy allowed the analysis of individual grains and localized phases. The analyses revealed clear compositional differences among the investigated mortars, mainly involving quartz-, calcite-, clay-rich, and cement-related phases, together with Raman markers deriving from carotenoid (beta-carotene)-containing biological colonization. The comparison between DRIFTS and µ-Raman data demonstrates the complementarity of the two techniques for rapid in situ screening of heterogeneous historical mortars. In particular, DRIFTS rapidly characterizes the overall molecular composition, whereas µ-Raman resolves individual mineral constituents and localized alteration products. Noteworthy, the identification of mineral phases, restoration materials, and biodeterioration markers provides a valuable basis for targeted analytical investigations and informed conservation planning.

From bell sound to architectural function: Quantitative vibroacoustic metrology applied to the Norman bell tower of Salerno Cathedral (Italy)

Fabrizio Barone, Rosa Fiorillo, Marco Casazza — Wed, 30 Sep 2026 00:00:00 +0000

This study formulates and assesses a measurement–model workflow for physical metrology applied to architectural heritage, using the Norman bell tower of Salerno Cathedral as a case study. Dominant spectral components of the 13th-century bell were identified through individually calibrated acoustic measurements, while a finite-element model provided the reference modal frequencies of the belfry-cell air volume. The two datasets were compared using perceptual frequency proximity based on the Equivalent Rectangular Bandwidth and restricted harmonic relations expressed in cents. Then, a Monte Carlo null model was used to determine whether the observed correspondence exceeded random spectral alignment. Sensitivity analyses addressed the effects of radiating aperture conditions and temperature-dependent variations in the speed of sound. Although the open-boundary model introduced mode-dependent frequency shifts, leakage, and modal reorganization, these effects did not materially alter the final interpretation. The study contributes an inspectable and transferable metrological chain linking measured quantities, model-derived outputs, influence factors, and statistical decision criteria for investigating sonic functions across the material and intangible dimensions of architectural heritage.

Dynamic Finite Element Modelling (DFEM) procedure for cultural heritage: Displacement-based reconstruction of the dynamical behaviour of the Roman bridge over the Savuto River

Fabrizio Barone, Armando Di Maio, Salvatore Antonio Fornaro, Marco Casazza — Tue, 29 Sep 2026 00:00:00 +0000

This study presents a metrological approach for investigating cultural heritage structures through Dynamic Finite Element Modelling (DFEM) procedure and displacement-based vibroacoustic monitoring. The Roman bridge over the Savuto River, Calabria, Italy, built in the 2^nd century BC along the Via Popilia, is analysed as a case study. Broadband mechanical seismometers were deployed to measure linear and angular displacements under ambient excitation, allowing modal frequencies, thermal deformation cycles, and local dynamic anomalies to be identified. The comparison between measured responses and numerical predictions showed good agreement for the main vibration modes, while persistent low-frequency discrepancies indicated that the visible geometry alone does not fully describe the structural system. These results support the hypothesis of an additional concealed substructure beneath the riverbed, and reveal asymmetric behaviour associated with twentieth-century restoration interventions. The study shows how high-sensitivity measurements can strengthen digital modelling by transforming dynamic response into metrological evidence for structural diagnosis and heritage interpretation.

Infrared thermography as a measurement tool for non-invasive stress assessment in canaries

Wed, 16 Sep 2026 00:00:00 +0000

Infrared thermography (IRT) is a non-contact and thermal imaging technique increasingly applied in engineering, biomedical, and veterinary sciences. By detecting infrared radiation emitted from living organisms, IRT enables real-time mapping of surface temperature distributions, offering physiological insights often inaccessible to conventional diagnostic methods. Unlike other imaging modalities that rely on electromagnetic radiation to visualize internal structures, IRT provides dynamic thermal sequences and continuous monitoring of physiological processes without discomfort for the subject. This study explores the application of IRT in canaries (Serinus Canaria), to quantitatively evaluate acute stress responses through surface thermal variations in different anatomical regions. Thermal images were acquired before and after handling, and three regions of interest (ROIs), namely the beak, the periocular area, and the body surface, were analyzed. The hypothesis was that handling-induced stress would produce measurable and region-specific peripheral temperature changes. Using a high-sensitivity thermal camera under controlled environmental conditions, temperature values were recorded before and after standardized gentle manipulation. Paired statistical analysis revealed significant post-handling temperature increases, with the highest relative variation observed in the beak region (3.52 %), followed by the body surface (2.99 %), and the periocular region (1.02 %). A one-way ANOVA performed on post-stress temperatures demonstrated a significant effect of region of interest (F (2,57) = 16.84, p < 0.001), with a large effect size (η² = 0.37). Post-hoc Tukey analysis confirmed that the beak exhibited significantly higher temperatures compared to both the body and the periocular regions. These findings demonstrate that IRT provides statistically robust and region-dependent thermal markers for acute handling stress. Beyond biological implications, this work emphasizes the importance of ROI selection, measurement repeatability, and quantitative statistical validation, positioning IRT as a rigorous and non-invasive measurement technique for stress assessment in small avian species.

From surface to subsurface: Integrating imaging techniques and laser profilometry in artworks study

Sat, 12 Sep 2026 00:00:00 +0000

This study aims to present the results obtained from the profilometric and reflectographic analyses of the painting on panel L’Ebbrezza di Noè, attributed to Antonio Bazzi (known as Il Sodoma), preserved at the Galleria Nazionale di Arte Antica in Palazzo Barberini (Rome, Italy). Utilizing an advanced integrated scanning system, we employed a high-resolution laser profilometer with a 405 nm laser line, a lateral resolution of 12.5 µm and a height resolution of 1.6 µm, along with a SWIR uncooled camera equipped with an InGaAs detector with a resolution of 320 × 256 pixels, operating within a spectral range from 900 to 1700 nm, to scan and analyze the artwork. By selecting significant details, we highlighted the potential of a multi-instrument approach in accurately interpreting the complex information revealed through diagnostic imaging of artworks. Specifically, profilometric images were compared with infrared and false-color images to determine whether hidden features beneath the paint layers can be detected through surface topography.

Evaluating the effects of gamma irradiation on early 20th-century paper for paper-based cultural heritage preservation using non-destructive and minimally destructive techniques

Mon, 21 Sep 2026 00:00:00 +0000

This study investigates the secondary effects of gamma irradiation on early 20th-century paper samples from historical books, aiming to evaluate the suitability of this method for preserving cultural heritage (CH) materials. In recent years, gamma irradiation has gained recognition as an effective decontamination approach, capable of eradicating biodeteriogens without the use of harmful chemicals or heat. However, concerns persist about potential alterations in the structural and chemical integrity of aged paper artifacts. To address these issues, a set of non-destructive and minimally destructive analytical techniques, such as micro-Raman, FTIR-ATR, and EPR spectroscopies, along with thermogravimetric analysis, was employed to monitor possible changes in the morphology, molecular structure, chemical composition, radical content, and thermal stability of the samples. Results indicate that gamma irradiation at doses below 10 kGy does not cause significant degradation in the physico-chemical properties of this kind of historical paper. These findings offer new insights into the effects of ionizing radiation on aged paper, and contribute to the development of safe, standardized irradiation protocols for CH conservation. Moreover, the study highlights the importance of combining multiple analytical techniques to ensure accurate diagnostics, reinforcing gamma irradiation as a reliable and practical tool for the long-term preservation of vulnerable paper-based heritage artifacts.

Less is more: Few-shot learning in 3D super resolution using synthetic CT images

Thu, 17 Sep 2026 00:00:00 +0000

In this work, we study data requirements and scaling behavior of super resolution (SR) machine learning networks on computed tomography (CT) scans of aluminum foam samples. The pipeline consists of pre-training a 3D U-Net model on purely synthetic data and fine-tuning this model on increasing quantities of real data. Synthetic data is produced by a shallow convolutional neural network (CNN), which learns real CT degradations. This degraded data is later used for training a 3D U-Net SR network in order to reduce manual alignment labor for training such models. Our results suggest that only a small fraction of the dataset is required for fine-tuning synthetic models and diminishing returns are observed after a few pairs. Furthermore, simply increasing the amount of real fine-tuning data does not consistently improve performance across the different data configurations. These findings indicate that dataset selection may be as important as dataset size when training SR models for CT enhancement.

X-ray computed tomography for non-destructive evaluation of steel wire ropes: Comparison of laboratory XCT configurations for image quality and damage visualization

Fri, 04 Sep 2026 00:00:00 +0000

Steel wire ropes are critical structural components whose internal damage often cannot be reliably assessed using conventional non-destructive testing methods. This study evaluates the applicability of laboratory X-ray computed microtomography (XCT) for detailed inspection of steel wire ropes by comparing three complementary XCT configurations: one employing a liquid-metal anode microfocus source with a large-area flat-panel detector, a conventional sealed-type microfocus tube with CMOS detector, and a high-power X-ray source coupled with scintillating screen and a laboratory camera. Intact and damaged rope specimens together with an individual fractured steel wire were investigated under various acquisition conditions. Image quality was quantitatively assessed using the contrast-to-noise ratio (CNR) and the full width at half maximum (FWHM) of the line spread function, complemented by qualitative evaluation of reconstructed three-dimensional models. The results demonstrate the influence of X-ray source characteristics and the acquisition parameters on image quality and defect detectability. Although the high-power system provided superior penetration capability and the highest CNR, its large focal point substantially limited the achievable spatial resolution. In contrast, both microfocus configurations enabled reliable visualization of individual wires and internal damage features, with image quality strongly dependent on the number of acquired projections. The presented comparison provides practical guidance for selecting appropriate laboratory XCT configurations for non-destructive evaluation of steel wire ropes and similar highly attenuating engineering components.

Performance analysis of an asynchronous time integration scheme for split Hopkinson pressure bar simulations

Radim Dvořák, Lukáš Kocian, Petr Koudelka — Fri, 18 Sep 2026 00:00:00 +0000

We present a performance analysis of an asynchronous explicit time integration framework for partitioned elastodynamic problems with strongly heterogeneous temporal scales, motivated by simulations of Split Hopkinson Pressure Bar (SHPB) experiments. The proposed approach allows individual subdomains to advance with different time increments, enabling the small nonlinear specimen to be integrated using the time step required for accuracy while the long elastic bars are advanced asynchronously with substantially larger time steps. Numerical comparisons with conventional synchronous explicit integration, including LS-DYNA, demonstrate that the proposed method preserves accuracy while significantly reducing computational cost. The study further shows that the performance gains increase with the disparity between the characteristic time scales of the coupled subdomains, making the approach particularly attractive for large-scale SHPB simulations involving long elastic bars. These results demonstrate the potential of asynchronous time integration as an efficient alternative to conventional explicit solvers for computationally demanding impact simulations.

Spiral X-ray computed tomography of long wooden samples: Influence of pitch and geometric calibration on reconstruction quality

Vaclav Rada, Daniel Vavřík, Jiři Kunecký, Daniel Kytýř — Fri, 04 Sep 2026 00:00:00 +0000

X-ray computed tomography (XCT) is widely used for three-dimensional characterization of material microstructure. In wood science, XCT increasingly serves as a tool for quantitative analysis of annual rings, porosity, and other structural features requiring high reconstruction fidelity, and geometrical consistency. Spiral XCT enables scanning of samples exceeding the detector field of view in height by combining continuous sample rotation with synchronized axial translation during acquisition. This work investigates the influence of mechanical alignment, motion synchronization, geometric calibration, and spiral pitch on the reconstruction quality of long wooden specimens.
Reconstruction fidelity depends on the agreement between the assumed spiral trajectory and the actual coupled rotational and axial motion during acquisition. Misalignment of the rotation axis with respect to the source–detector geometry, together with inaccuracies in axial translation or magnification calibration, may introduce geometric distortions, blurring, and loss of structural fidelity. The effect of spiral pitch, defined as the axial displacement per full rotation, was experimentally investigated by performing scans with different predefined pitch values. Increasing the spiral pitch reduced axial sampling density and projection overlap, resulting in progressively stronger interpolation artefacts and degradation of reconstruction quality.
The study further demonstrates the sensitivity of cone-beam spiral XCT reconstruction to accurate magnification calibration, as even small scaling errors lead to cumulative misregistration along the reconstructed volume. Reliable spiral XCT of long wooden samples therefore requires accurate geometric calibration, stable synchronization of the rotational and axial motions, and an appropriately selected spiral pitch.

Monitoring of crack propagation in anisotropic rocks during compressive strength testing using gas permeability measurements

Martin Vavro, Leona Vavro, Lukáš Kubina, Karel Sosna — Wed, 23 Sep 2026 00:00:00 +0000

Porosity and related fluid permeability are key parameters that influence a number of other physical and mechanical properties of rocks and therefore have an impact on their specific engineering uses. Porosity and permeability depend on the microstructure of the rock, mainly on the size distribution, shape, and mutual connectivity of the pores in the rock matter, but also on the degree of rock failure caused by the presence of microcracks. This close connection between the rock's permeability and the presence of a microcrack network in the rock means, in other words, that changes in permeability during loading can serve as a measure for monitoring crack initiation and propagation. In the presented research, biotite migmatite, a metamorphic rock with a well-developed plane-parallel structure, was used for this purpose with the aim of simultaneously assessing the influence of textural anisotropy on the process of crack formation and development. It was found that an increase in gas permeability due to the formation of microcracks occurs when ca. 60 to 90 % of the maximum loading force is achieved, mostly depending on the spatial relationship between the orientation of anisotropy planes and the direction of the applied loading force.

Dynamic and quasi-static characterization and Cowper–Symonds material model calibration of photopolymer resins produced by stereolithography

Tue, 29 Sep 2026 00:00:00 +0000

Photopolymer resins produced by stereolithography (SLA) are widely used for manufacturing lattice structures and mechanical metamaterials intended for experimental validation of numerically designed structures. Reliable simulations of their response under dynamic loading require constitutive models capable of describing strain-rate-dependent material behavior; however, suitable experimental data for commercially available SLA resins remain limited.
This study presents the experimental characterization and Cowper--Symonds model calibration of two SLA printing materials: Phrozen Aqua Blue Resin and Phrozen High-Resolution RPG Resin. Cylindrical bulk specimens were manufactured by SLA and tested under quasi-static compression and high-strain-rate compression using a split Hopkinson pressure bar apparatus. The resulting stress–strain curves were used to evaluate the strain-rate sensitivity of both resins. Yield stress values determined at different strain rates served as input data for the calibration of the Cowper--Symonds parameters. The calibrated material parameters are intended for implementation in LS-DYNA together with the quasi-static material response, for explicit simulations of dynamically loaded SLA-printed structures. The results provide experimentally derived material data for future numerical simulations of SLA-printed lattice structures and mechanical metamaterials.

Journal contacts

Dirk Röske — Mon, 28 Sep 2026 00:00:00 +0000

Introductory notes for the Acta IMEKO third issue in 2026

Francesco Lamonaca — Wed, 30 Sep 2026 00:00:00 +0000

Introduction to the Acta IMEKO Thematic Issue ‘Infrared thermography: challenges and new frontiers’

Antonio Cannuli, Roberto Montanini — Wed, 30 Sep 2026 00:00:00 +0000

Introduction to the Acta IMEKO Thematic Issue '2025 IMEKO TC26 International Conference on Metrology for Archaeology and Cultural Heritage'

Fabio Leccese — Mon, 28 Sep 2026 00:00:00 +0000

Introduction to the Acta IMEKO Thematic Issue 'IMEKO TC15 Collegium 2026' – Part 1

Daniel Kytýř, Emina Hadzalic, Zvonimir Tomičević — Tue, 29 Sep 2026 00:00:00 +0000

This Thematic Issue of Acta IMEKO presents the first collection of papers originating from the IMEKO TC15 Collegium 2026, held in Prague, Czech Republic, from 10 to 12 June 2026. The Collegium was organised by the Institute of Theoretical and Applied Mechanics of the Czech Academy of Sciences under the auspices of IMEKO Technical Committee 15 – Experimental Mechanics.