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Paper des Monats
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Temperature Compensation Strategies for Lamb Wave Inspection using Distributed Sensor Networks
(2022)
The application of temperature compensation strategies is crucial in structural health monitoring approaches based on guided waves. Actually, the varying temperature influences the performance of the inspection system inducing false alarms or missed detection, with a consequent reduction of reliability. This paper quantitatively describes a method to compensate the temperature effect, namely the optimal baseline selection (OBS), extending its application to the case of distributed sensor networks (DSN). The effect of temperature separation between baseline time-traces in OBS are investigated considering multiple couples of sensors employed in the DSN. A combined strategy that uses both OBS and frequent value warning is considered. Theoretical results are compared, using data from two several experiments, which use different frequency analysis with either predominantly A0 mode or S0 mode data or both. The focus is given on the fact that different paths are available in a sensor network and several possible combination of results are available. Nonetheless, introducing a frequent value warning it is possible to increase the efficiency of the OBS approach making use of fewer signal processing algorithms. These confirm that the performance of OBS quantitatively agrees with predictions and also demonstrate that the use of compensation strategies improve detectability of damage.
A systematic study has been carried out to investigate the neutron transmission signal as a function of sample temperature. In particular, the experimentally determined wavelength-dependent neutron attenuation spectra for a martensitic steel at temperatures ranging from 21 to 700°C are compared with simulated data. A theoretical description that includes the Debye–Waller factor in order to describe the temperature influence on the neutron cross sections was implemented in the nxsPlotter software and used for the simulations. The analysis of the attenuation coefficients at varying temperatures shows that the missing contributions due to elastic and inelastic scattering can be clearly distinguished: while the elastically scattered intensities decrease with higher temperatures, the inelastically scattered intensities increase, and the two can be separated from each other by analysing unique sharp features in the form of Bragg edges. This study presents the first systematic approach to quantify this effect and can serve as a basis , for example, to correct measurements taken during in situ heat treatments, in many cases being a prerequisite for obtaining quantifiable results.
Tempo-spectral multiplexing in flow cytometry with lifetime detection using QD-encoded polymer beads
(2020)
Semiconductor quantum dots (QDs) embedded into polymer microbeads are known to be very attractive emitters for spectral multiplexing and colour encoding. Their luminescence lifetimes or decay kinetics have been, however, rarely exploited as encoding parameter, although they cover time ranges which are not easily accessible with other luminophores. We demonstrate here the potential of QDs made from II/VI semiconductors with luminescence lifetimes of several 10 ns to expand the lifetime range of organic encoding luminophores in multiplexing applications using time-resolved flow cytometry (LT-FCM). For this purpose, two different types of QD-loaded beads were prepared and characterized by photoluminescence measurements on the ensemble level and by single-particle confocal laser scanning microscopy. Subsequently, these lifetime-encoded microbeads were combined with dye-encoded microparticles in systematic studies to demonstrate the potential of these QDs to increase the number of lifetime codes for lifetime multiplexing and combined multiplexing in the time and colour domain (tempo-spectral multiplexing). These studies were done with a recently developed novel luminescence lifetime flow cytometer (LT-FCM setup) operating in the time-domain, that presents an alternative to reports on phase-sensitive lifetime detection in flow cytometry.
In civil engineering, the laser-induced breakdown spectroscopy has been applied as a fast and reliable method for a quantitative evaluation of concrete cores. Due to a two-dimensional scanning, the heterogeneity of concrete can be evaluated and elements like Cl, Na, and S are related to the cement matrix only. This study deals with the temporal evaluation and imaging of laser-induced plasmas on cement-based materials, in order to investigate the impact of aggregates with diffrent grain size on the spectral response in LIBS.
The quality of research antibodies is an issue for decades. Although several papers have been published to improve the situation, their impact seems to be limited. This publication makes the effort to simplify the description of validation criteria in a way that the occasional antibody user is able to assess the validation level of an immunochemical reagent. A simple, 1-page checklist is supplied for the practical application of these criteria.
Fluorides are well-known as wood preservatives. One of the limitations of fluoride-based wood preservatives is their high leachability. Alternative to current fluoride salts such as NaF used in wood protection are low water-soluble fluorides. However, impregnation of low water-soluble fluorides into wood poses a challenge. To address this challenge, low water-soluble fluorides like calcium fluoride (CaF2) and magnesium fluoride (MgF2) were synthesized as nanoparticles via the fluorolytic sol−gel synthesis and then impregnated into wood specimens. In this study, the toxicity of nano metal fluorides was assessed by termite mortality, mass loss and visual analysis of treated specimens after eight weeks of exposure to termites, Coptotermes formosanus. Nano metal fluorides with sol concentrations of 0.5 M and higher were found to be effective against termites resulting in 100% termite mortality and significantly inhibited termite feeding. Among the formulations tested, the least damage was found for specimens treated with combinations of CaF2 and MgF2 with an average mass loss less than 1% and visual rating of “1”. These results demonstrate the efficacy of low water-soluble nano metal fluorides to protect wood from termite attack.
The process of ensuring reliability of NDT applications contains various aspects, such as determining the performance and probability of success, the uncertainty in measurement, the provision of clear and functional procedures and ensuring the correct application accordingly. Test specimens have become powerful elements in supporting many of these aspects. Within the committee for NDT in Civil Engineering (NDT-CE) of the German Society for Nondestructive Testing (DGZfP), the subcommittee on Quality Assurance (UA-QS) therefore addresses the design and the integration of test specimens in the quality assurance process. Depending on the specific purpose, the requirements on test specimens can vary significantly based on the defined simulated scenario. The most prominent purposes of test specimens might be seen in providing references for inspection systems in regard to function control, calibration and validation. Further aspects can be parametric studies, basic investigation of physical principles related to NDT or a simplified and therefore comprehensive demonstration of inspection concepts (e.g. for teaching purposes). The specific purpose of a test specimen dictates the requirements regarding its conception, including the exact design, the material or the fabrication accuracy and the conditioning. In the development of a general guideline by the UA-QS for application-specific procedures and their validation, the use of test specimens is addressed and specific concepts for the design of test specimens are made. This includes the analysis of the measurement process regarding any given application, deriving an adequate calibration approach for it and designing test specimens (calibration specimens) accordingly. Furthermore, it includes the validation of the procedure taking into account all conditions related to the specific application in the field. The validation requires a statistically sufficient number of trials. Thorough evaluation of each trial can only be established if the ground-truth is known. Therefore, test specimens providing a realistic but controlled simulation of the inspection problem are valuable and indispensable elements in the validation process. The requirement of being fully realistic will often not be possible to fulfill due to practical restrictions. Any aspect that cannot be included in the simulation realistically needs to be simulated conservatively. This again, requires a sufficient understanding of the inspection principle and technique to ensure conservativeness. Among other quality-assurance-related aspects, the UA-QS establishes concepts and guidelines regarding sound and efficient approaches for the specific purposes of test specimens. This subcommittee brings together representatives of different Groups along the entire value chain of NDT-CE, including researchers, practitioners, manufacturers and clients. They all work together in establishing a common understanding and level of quality assurance in the industry.
One of the objectives of the EU Project EC4SafeNano (European Centre for Risk Management and Safe Innovation in Nanomaterials & Nanotechnologies) was to test and benchmark the services in order to check their relevance to address identified stakeholder needs, but also to evaluate the governance of the structure delivering the proposed services. The aim is to demonstrate the technical relevance of the services and the overall open structure organisation, including governance rules and operating procedures, by answering relevant identified questions (case studies) selected by a panel of stakeholders. Therefore, a significant part of the project will be devoted to this demonstration of the operational and functional basis of the organized network.
Corrosion of concrete reinforcement is one of the major damage mechanisms affecting both the load-bearing capacity and the serviceability of reinforced concrete structures significantly. The challenge of detecting corrosion is that the corrosion process in its various forms is not immediately visible, especially in the corrosion initiation phase inside the concrete. When externally discernible damages are observed during visual inspections on the structure, the extent of the damage inside the concrete is often already significant. Corrosion caused by carbonation often leads to severe discoloration of the surface or even large-area spalling of the concrete cover. In contrast, chloride-induced corrosion is usually difficult to observe visually, but can cause much more serious damage in less time. The effect occurs locally and can lead to weakening of the cross-section of the reinforcement. This, in turn, can cause sudden structural collapses without prior notice. Therefore, it is important to investigate whether there is protection against corrosion of the reinforcement in the concrete and to detect active corrosion in the structure at an early stage.
In the meanwhile, various non-destructive and minimally invasive testing methods are available to evaluate the resistance to penetration of corrosion-promoting pollutants and to detect active corrosion. In this paper, a bridge crossing the river Regen (Germany) is used as a case-study to demonstrate how the information obtained applying different testing methods can be combined and evaluated in the context of structural reassessments. Both the results of the permeability testing (Torrent tester) and the electrical resistance measurement (Wenner probe) are considered, as well as active corrosion areas are localized using the half-cell potential mapping combined with the concrete cover measurement with the eddy current method and ground penetrating radar (GPR). The results are evaluated using drill cores and in addition laser-induced breakdown spectroscopy (LIBS) was applied to obtain information about possible ion transport in the concrete.
Corrosion of concrete reinforcement is one of the major damage mechanisms affecting both the load-bearing capacity and the serviceability of re-inforced concrete structures significantly. When externally discernible damages are observed during visual inspections on the structure, the extent of the damage inside the concrete is often already significant. Corrosion caused by carbonation often leads to severe discoloration of the surface or even large-area spalling of the concrete cover. In contrast, chloride-induced corrosion is usually difficult to observe visually but can cause much more serious damage in less time. The effect occurs locally and can lead to weakening of the cross-section of the reinforce-ment. This, in turn, can cause sudden structural collapses without prior notice.
In the meanwhile, various non-destructive and minimally invasive testing methods are available to evaluate the resistance to penetration of corrosion-pro-moting pollutants and to detect active corrosion. In this paper, a bridge crossing the river Regen is used as a case-study to demonstrate how the information ob-tained applying different testing methods can be combined and evaluated in the context of structural reassessments. Both the results of the permeability testing and the electrical resistance measurement are considered, as well as active corro-sion areas are localized using the half-cell potential mapping combined with the concrete cover measurement with the eddy current method and ground penetrat-ing radar. The results are evaluated using drill cores and in addition laser-induced breakdown spectroscopy was applied to obtain information about possible chlo-ride ion transport into the concrete.
Although layer-based additive manufacturing methods such as laser powder bed fusion (PBF-LB) offer an immense geometrical freedom in design, they are typically subject to a build-up of internal stress (i.e. thermal stress) during manufacturing. As a consequence, significant residual stress (RS) is retained in the final part as a footprint of these internal stresses. Furthermore, localized melting and solidification inherently induce columnar-type grain growth accompanied by crystallographic texture. Although diffraction-based methods are commonly used to determine the RS distribution in PBF-LB parts, such features pose metrological challenges in their application. In theory, preferred grain orientation invalidates the hypothesis of isotropic material behavior underlying the common methods to determine RS. In this work, more refined methods are employed to determine RS in PBF-LB/M/IN718 prisms, based on crystallographic texture data. In fact, the employment of direction-dependent elastic constants (i.e. stress factors) for the calculation of RS results in insignificant differences from conventional approaches based on the hypothesis of isotropic mechanical properties. It can be concluded that this result is directly linked to the fact that the {311} lattice planes typically used for RS analysis in nickel-based alloys have high multiplicity and less strong texture intensities compared with other lattice planes. It is also found that the length of the laser scan vectors determines the surface RS distribution in prisms prior to their removal from the baseplate. On removal from the baseplate the surface RS considerably relaxes and/or redistributes; a combination of the geometry and the scanning strategy dictates the sub-surface RS distribution.
The 2023 Nobel Prize in Chemistry was awarded to Aleksey I. Ekimov (prize share 1/3), Louis E. Brus (prize share 1/3), and Moungi G. Bawendi (prize share 1/3) for groundbreaking inventions in the field of nanotechnology, i.e., for the discovery and synthesis of semiconductor nanocrystals, also termed quantum dots, that exhibit size-dependent physicochemical properties enabled by quantum size effects. This feature article summarizes the main milestones of the discoveries and developments of quantum dots that paved the road to their versatile applications in solid-state lighting, display technology, energy conversion, medical diagnostics, bioimaging, and image-guided surgery.
Most factors acting on concrete rheology work at an extremely small-scale level. Influencing factors in the millimetre or centimetre area are essentially restricted to sand and aggregates. The latter, however, make up 50 to 70% of the total volume of most concretes – a fact often ignored in research on controlling concrete processing properties.
Whereas suitably chosen concrete admixtures and additives can influence rheology in a very targeted manner, sand and aggregates are less suitable for controlling rheology but nonetheless contribute to the rheology of the Overall system. The actions of sand and aggregate can impose themselves upon the actions of admixtures and additives
and, in unfavourable circumstances, even render them redundant. For this reason, any results concerning the processability of binding agent systems can only be transferred to concrete with great care. It is important to better understand the action of sand and aggregates in order to be able to harmonise them in such a way that they complement the action of superplasticisers positively, instead of
working against them. Savings on costs can also be made by this targeted fine-tuning.
The rails of modern railways face an enormous wear and tear from ever increasing train speeds and loads. This necessitates diligent non-destructive testing for defects of the entire railway system.
Non-destructive testing of rail tracks is carried out by rail inspection trains equipped with ultrasonic and eddy current test devices. However, the evaluation of the gathered data is mainly done manually with a strong focus on ultrasonic data, and defects are checked on-site using hand-held testing equipment. Maintenance measures are derived based on these on-site findings.
The aim of the AIFRI project (Artificial Intelligence For Rail Inspection) is to
- increase the degree of automation of the inspection process, from the evaluation of the data to the planning of maintenance measures,
- increase the accuracy of defect detection,
- automatically classify detected indications into risk classes.
These aims will be achieved by training a neural network for defect detection and classification. Since the current testing data is unbalanced, insufficiently labeled and largely unverified we will supplement fused, simulated eddy current and ultrasonic testing data in form of a configurable digital twin.
This paper reports the outcome of an interdisciplinary team’s application of multispectral imaging techniques and material analysis to a music fragment from the first decades of the fifteenth century: Atri, Archivio Capitolare, Museo della Basilica Cattedrale, Biblioteca del Capitolo della Cattedrale, Frammento 17. This important parchment leaf has rarely been investigated since its discovery 45 years ago. Thanks to the applied techniques and methods (such as the evaluation of the data using the fingerprint model), it is now possible to discuss new evidence supporting conclusions regarding the fragment’s origin and afterlife.
The BAM Data Store
(2023)
As a partner in several NFDI consortia, the Bundesanstalt für Materialforschung und -prüfung (BAM, German federal institute for materials science and testing) contributes to research data standardization efforts in various domains of materials science and engineering (MSE). To implement a central research data management (RDM) infrastructure that meets the requirements of MSE groups at BAM, we initiated the Data Store pilot project in 2021. The resulting infrastructure should enable researchers to digitally document research processes and store related data in a standardized and interoperable manner. As a software solution, we chose openBIS, an open-source framework that is increasingly being used for RDM in MSE communities.
The pilot project was conducted for one year with five research groups across different organizational units and MSE disciplines. The main results are presented for the use case “nanoPlattform”. The group registered experimental steps and linked associated instruments and chemicals in the Data Store to ensure full traceability of data related to the synthesis of ~400 nanomaterials. The system also supported researchers in implementing RDM practices in their workflows, e.g., by automating data import and documentation and by integrating infrastructure for data analysis.
Based on the promising results of the pilot phase, we will roll out the Data Store as the central RDM infrastructure of BAM starting in 2023. We further aim to develop openBIS plugins, metadata standards, and RDM workflows to contribute to the openBIS community and to foster RDM in MSE.
In view of the increasing digitization of research and the use of data-intensive measurement and analysis methods, research institutions and their staff are faced with the challenge of documenting a constantly growing volume of data in a comprehensible manner, archiving them for the long term, and making them available for discovery and re-use by others in accordance with the FAIR principles. At BAM, we aim to facilitate the integration of research data management (RDM) strategies during the whole research cycle from the creation and standardized description of materials datasets to their publication in open repositories. To this end, we present the BAM Data Store, a central system for internal RDM that fulfills the heterogenous demands of materials science and engineering labs. The BAM Data Store is based on openBIS, an open-source software developed by the ETH Zurich that has originally been created for life science laboratories but that has since been deployed in a variety of research domains. The software offers a browser-based user interface for the digital representation of lab inventory entities (e.g., samples, chemicals, instruments, and protocols) and an electronic lab notebook for the standardized documentation of experiments and analyses.
To investigate whether openBIS is a suitable framework for the BAM Data Store, we carried out a pilot phase during which five research groups with employees from 16 different BAM divisions were introduced to the software. The pilot groups were chosen to represent a diverse array of domain use cases and RDM requirements (e.g., small vs big data volume, heterogenous vs structured data types) as well as varying levels of prior IT knowledge on the users’ side.
Overall, the results of the pilot phase are promising: While the creation of custom data structures and metadata schemas can be time-intensive and requires the involvement of domain experts, the system offers specific benefits in the form of a simplified documentation and automation of research processes, as well as constituting a basis for data-driven analysis. In this way, heterogeneous research workflows in various materials science research domains could be implemented, from the synthesis and characterization of nanomaterials to the monitoring of engineering structures. In addition to the technical deployment and the development of domain-specific metadata standards, the pilot phase also highlighted the need for suitable institutional infrastructures, processes, and role models. An institute-wide rollout of the BAM Data Store is currently being planned.