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Evaluation of features and channels of electroencephalographic signals for biometric systems
Full text linkBiometric systems are essential tools in modern society where most of our personal information lives in digital form. Although there is a significant variety of biometrics, electroencephalogram (EEG) signals are a useful technique to guarantee that the person is alive, they are universal, and not falsifiable. Nevertheless, EEG processing needs to address some challenges to become a viable technique to build production-ready biometric systems. These challenges include the adequate selection of features and channels that maximize the quality of the results and optimize resources. This work provides an analysis of which are the most important features and channels for the correct operation of a biometric system. The experimental analysis worked with two datasets and evaluated 19 features belonging to three groups, wavelet-based, spectral, and complexity. Five classifiers were trained: multilayer perceptron, AdaBoost, random forest, support vector machine, and K-nearest neighbors. The results found that the best feature for developing a biometric system is the standard deviation extracted from the coefficients of a three-level discrete wavelet transform. Additionally, the experimental results with the two datasets showed that the proposed method for channel selection can reduce the necessary number of channels while maintaining its performance. Our results, from one of the datasets, showed a reduction of 21 channels (from 32 to 11) and indicated that the best channels to develop biometric systems seem to be those located on the central area of the scalp
Reuse and remanufacturing of insulated glass units
Full text linkMany office and residential buildings in Europe need to be renovated in the near future to meet current energy efficiency requirements. This often comes down to updating the insulation performance of the building envelope including the windows. Most “old” windows consist of a frame and a double insulated glass unit (IGU) or even monolithic glass panes – typically without any low-e coating. These non-coated double glazings have a Ug-value of 2.7 W/m²K (single glazing even 5.2 W/m²K). Modern coated triple glazed IGUs provide Ug-values of up to 0.5 W/m²K.
This paper deals with the question of how old insulating glass units can be re manufactured to match the state of the art in terms of the energy efficiency. For this purpose, dismounted IGUs from the 1980s are used. After analyzing the remaining functionality, the double IGUs are disassembled. The single glass pane is cleaned, and the old edge sealing is removed. The old glass pane is combined with a new coated low-e glass and a spacer system to form a new upgraded IGU with warm edge technology. This study demonstrates that remanufactured IGUs can achieve the performance of IGUs made from new glass
Direct visualization of stacking-selective self-intercalation in epitaxial Nb₁₊ₓSe₂ films
No full textTwo-dimensional (2D) van der Waals (vdW) materials offer rich tuning opportunities generated by different stacking configurations or by introducing intercalants into the vdW gaps. Current knowledge of the interplay between stacking polytypes and intercalation often relies on macroscopically averaged probes, which fail to pinpoint the exact atomic position and chemical state of the intercalants in real space. Here, by using atomic-resolution electron energy-loss spectroscopy in a scanning transmission electron microscope, we visualize a stacking-selective self-intercalation phenomenon in thin films of the transition-metal dichalcogenide (TMDC) Nb₁₊ₓSe₂. We observe robust contrasts between 180°-stacked layers with large amounts of Nb intercalants inside their vdW gaps and 0°-stacked layers with little detectable intercalants inside their vdW gaps, coexisting on the atomic scale. First-principles calculations suggest that the films lie at the boundary of a phase transition from 0° to 180° stacking when the intercalant concentration x exceeds ~0.25, which we could attain in our films due to specific kinetic pathways. Our results offer not only renewed mechanistic insights into stacking and intercalation, but also open up prospects for engineering the functionality of TMDCs via stacking-selective self-intercalation
All black: a microplastic extraction combined with colour-based analysis allows identification and characterisation of tire wear particles (TWP) in soils
Full text linkWhile tire wear particles (TWP) have been estimated to represent more than 90% of the total microplastic (MP) emitted in European countries and may have environmental health effects, only few data about TWP concentrations and characteristics are available today. The lack of data stems from the fact that no standardized, cost efficient or accessible extraction and identification method is available yet. We present a method allowing the extraction of TWP from soil, performing analysis with a conventional optical microscope and a machine learning approach to identify TWP in soil based on their colour. The lowest size of TWP which could be measured reliably with an acceptable recovery using our experimental set-up was 35 µm. Further improvements would be possible given more advanced technical infrastructure (higher optical magnification and image quality). Our method showed a mean recovery of 85% in the 35–2000 µm particle size range and no blank contamination. We tested for possible interference from charcoal (as another black soil component with similar properties) in the soils and found a reduction of the interference from charcoal by 92% during extraction. We applied our method to a highway adjacent soil at 1 m, 2 m, 5 m, and 10 m and detected TWP in all samples with a tendency to higher concentrations at 1 m and 2 m from the road compared to 10 m from the road. The observed TWP concentrations were in the same order of magnitude as what was previously reported in literature in highway adjacent soils. These results demonstrate the potential of the method to provide quantitative data on the occurrence and characteristics of TWP in the environment. The method can be easily implemented in many labs, and help to address our knowledge gap regarding TWP concentrations in soils
An integrated coupled oscillator network to solve optimization problems
Full text linkSolving combinatorial optimization problems is essential in scientific, technological, and engineering applications, but can be very time and energy-consuming using classical algorithms executed on digital processors. Oscillator-based Ising machines offer a promising alternative by exploiting the analog coupling between electrical oscillators to solve such optimization problems more efficiently. Here we present the design and the capabilities of our scalable approach to solve Ising and quadratic unconstrained binary optimization problems. This approach includes routable oscillator connections to simplify the time-consuming embedding of the problem into the oscillator network. Our manufactured silicon chip, featuring 1440 oscillators implemented in a 28 nm technology, demonstrates the ability to solve optimization problems in 950 ns while consuming typically 319 μW per node. A frequency, phase, and delay calibration ensures robustness against manufacturing variations. The system is evaluated with multiple sets of benchmark problems to analyze the sensitivity for parameters such as the coupling strength or frequency
Non-linear enhancement of ultrafast X-ray diffraction through transient resonances
No full textDiffraction-before-destruction imaging with ultrashort X-ray pulses can visualize non-equilibrium processes, such as chemical reactions, with sub-femtosecond precision in the native environment. Here, a nanospecimen diffracts a single X-ray flash before it disintegrates. The sample structure can be reconstructed from the coherent diffraction image (CDI). State-of-the-art X-ray snapshots lack high spatial resolution because of weak diffraction signal. Bleaching effects from photo-ionization significantly restrain image brightness scaling. We find that non-linear transient ion resonances can overcome this barrier if X-ray laser pulses are shorter than in most experiments. We compared snapshots from individual ≈ 100 nm Xe nanoparticles as a function of pulse duration and incoming X-ray fluence. Our experimental results and Monte Carlo simulations suggest that transient resonances can increase ionic scattering cross sections significantly beyond literature values. This provides a novel avenue towards substantial improvement of the spatial resolution in CDI in combination with sub-femtosecond temporal precision at the nanoscale
Investigation of Interaction Mechanisms between Hot Mix Asphalt and Paver Screed
Full text linkThe durability of asphalt pavements under traffic loads is significantly influenced by the compaction quality during construction. Poor compaction can lead to early pavement failure through cracking, rutting, or grain breakouts. The initial compaction stage performed by the asphalt paver is particularly critical, as subsequent roller compaction cannot correct errors at this stage. However, the complex interaction between the paver screed and hot mix asphalt, coupled with external factors like the delivery temperature of the asphalt mix, makes it difficult to achieve optimal compaction settings. This study addresses the knowledge gaps surrounding the precompaction process by analyzing the interaction between the paver screed and hot mix asphalt. A multi-faceted approach was adopted to achieve this, consisting of a comprehensive laboratory program, field trials, and a full-scale paver simulation using discrete element methods. The laboratory program examined different asphalt mixtures to evaluate the influence of temperature and asphalt mix type on various pre-defined asphalt paving properties. Field trials focused on understanding the effects of tamper and vibratory unit speeds, on the paving outcomes. Lastly, the discrete element simulation provided insights into the flow behavior and material movements during paving. The laboratory findings show that asphalt mix temperature impacts flow behavior, pre-compaction resistance, and friction. The field trials revealed that tamper speed significantly affects layer thickness and compaction, while the vibratory unit showed only a minor influence on the paving outcomes. The simulation results identify two primary material flow directions in the auger tunnel, driven by auger movements, with key grain rearrangement occurring near the tamper. Furthermore, the analysis emphasizes the importance of the tamper movement in achieving optimal compaction and critical wear areas on machine components. Based on these insights, recommendations for machine and process optimization were provided to enhance paving practices
ULtimate MAGnetic characterization (ULMAG) at the ID12 beamline of ESRF: from element‐specific properties to macroscopic functionalities
No full textWe present a novel instrument designed for advanced magnetic study, installed at the ID12 beamline of the European Synchrotron Radiation Facility in Grenoble, France. This instrument offers the unique capability to simultaneously measure element‐specific microscopic and macroscopic properties related to the magnetic, electronic and structural characteristics of materials. In addition to X‐ray absorption, X‐ray magnetic circular dichroism alongside X‐ray diffraction patterns, the macroscopic magnetization, volume changes, caloric properties and electrical resistivity of magnetic materials could be measured strictly under the same experimental conditions as a function of both magnetic field (up to ±7 T) and temperature (ranging from 2.05 K to 325 K). To demonstrate the capability of this new instrument, we present two case studies highlighting its performance in investigating first‐order magneto‐structural phase transitions, namely in DyCo₂ and FeRh alloys
Categorization and Abstract Similarity in Chess
No full textChess experts remember meaningful chess positions bet-ter than novices (de Groot, 1978; Chase & Simon,1973). This can be explained with a larger numberof chunks in experts' long-term memory (Gobet & Simon, 1998). These chunks are mainly based on visual representations - that is, pieces on squares. However, a recent experiment highlighted that experts prefer to group chess positions by abstract similarities that cannot be explained purely visually (Linhares & Brum,2007). Based on these data it was claimed that chess expertise, in addition to chunks, crucially relies on abstraction and analogies. These data and the conclusions were heavily criticized because the instructions strongly biased the participants to group positions in a certain way (Bilalić & Gobet, 2009). Here, we successfully replicated this experiment with less explicit instructions. In addition, we collected category labels for the groupings that allowed us to explore the abstract principles that participants used
Die Rolle von Klimaclubs in der internationalen Klimapolitik
No full textDie von der Hans-Böckler-Stiftung durch ein Promotionsstipendium geförderte Arbeit untersucht das Aufkommen von Klimaclubs im internationalen Mehrebenensystem, in denen sich ambitionierte Staaten zum minilateralen Klimaschutz zusammenschließen.
Dabei wird der Frage nachgegangen, inwieweit Klimaclubs eine effektive und legitime Ergänzung zu zwischenstaatlichen Verhandlungen auf Ebene der Vereinten Nationen darstellen können.
Vor diesem Hintergrund gliedert sich die Arbeit wie folgt:
Zu Beginn erfolgt eine knappe Darstellung des Ausmaßes des Klimawandels und seiner potenziellen Folgen. Daran schließt sich eine Analyse der Problemstruktur an, die die Komplexität möglicher Lösungswege deutlich macht.
Ein historischer Abriss der internationalen Klimapolitik entlang der klimapolitischen Wegmarken gibt anschließend einen Überblick darüber, mit welchen unterschiedlichen Rationalitäten zu verschiedenen Zeiten versucht wurde, das Problem zu bewältigen.
Das Theoriekapitel dient als konzeptioneller Rahmen und theoriegeleitete Vorbereitung für den empirischen Teil dieser Arbeit. Mit der Theorie zur Bereitstellung von Kollektivgütern werden Erklärungsansätze für die von der Wissenschaft immer wieder als unzureichend angemahnte Klimapolitik geliefert. Darüber hinaus wird erörtert, welchen Beitrag die Club-Governance zur Bereitstellung von Kollektivgütern leisten kann und welche Rolle Legitimität und Effektivität dabei spielen.
Im empirischen Teil dieser Arbeit werden die theoretischen Überlegungen aufgegriffen und aufgezeigt, wie Club-Governance in Politikfeldern außerhalb der Klimapolitik Anwendung findet. Im Anschluss wird der Fokus auf Klimaclubs gerückt. Dabei wird untersucht, wie die zuvor aus theorieperspektivischer Sicht diskutierte Club-Governance in der klimapolitischen Praxis genutzt werden kann und welche Aspekte der Legitimität und Effektivität dabei zu berücksichtigen sind.
Um den unterschiedlichen Begründungen und Handlungslogiken für Klimaclubs Rechnung zu tragen, wird die theoretische Debatte und die erste teils analytische, teils empirische Bestandsaufnahme aufgegriffen und im Kontext der Forschungsfragen eine Typologisierung von Klimaclubs vorgenommen.
Abschließend erfolgt eine Zusammenfassung der Erkenntnisse sowie eine kritische Reflexion der Ergebnisse und angewandten Methoden. Ferner werden Parallelen zu allgemeinen Debatten der
Internationalen Beziehungen aufgezeigt und die Policyrelevanz der Ergebnisse sowie mögliche Anknüpfungspunkte für zukünftige Forschung zum Themenfeld dargelegt.
Die vorliegende Arbeit schließt eine Forschungslücke, da zwar auch andere Studien einen Fokus auf Klimaclubs legen, diese jedoch selten konsequent an Theorien rationaler Entscheidungsfindung anknüpfen und nur begrenzt Aspekte der Legitimität berücksichtigen. Zudem konnte - aufgrund des jungen Alters vieler Klimaclubs - bislang kein umfassendes Bild der Klimaclub-Landschaft gezeichnet werden