A coalgebraic perspective on minimization, determinization and behavioural metrics

Coalgebra offers a unified theory of state based systems, including infinite streams, labelled transition systems and deterministic automata. In this paper, we use the coalgebraic view on systems to derive, in a uniform way, abstract procedures for checking behavioural equivalence in coalgebras, which perform (a combination of) minimization and determinization in the system. First, we show that for coalgebras on categories equipped with factorization structures, there exists an abstract procedure for equivalence checking. For instance, when considering epi-mono factorizations in the category of sets and functions, this procedure corresponds to the usual (coalgebraic) minimization algorithm and two states are behaviourally equivalent iff they are mapped to the same state in the minimized coalgebra. Second, motivated by several examples, we consider coalgebras on categories without suitable factorization structures: under certain conditions, it is possible to apply the above procedure after transforming coalgebras with reflections. This transformation can be thought of as some kind of determinization. Finally, we show that the result of the procedure also induces a pseudo-metric on the states, in such a way that the distance between each pair of states is minimized

Influence of pin size on tensile and fatigue behavior of TI-CFRP hybrid structures produced by laser additive manufacturing

This paper contains mechanical investigations of metallic fabric-penetrating interfaces produced by powder-bed-based laser additive manufacturing and vacuum-assisted resin transfer moulding. Therefore, different fabric penetrations (pins) have been created which vary in length. These penetrative interfaces have been studied in quasi-static tensile (shear) tests and fatigue tests. Deformation and damage processes were determined during tensile and fatigue loading by measurement of the local strain distribution, utilizing a 3D-digital image correlation (DIC) system. Additionally, light microscopic and scanning electron microscopic (SEM) investigations were carried out in order to assess the damage mechanisms and fracture surfaces. The quasi-static tests revealed that tensile shear strength increased by 503 % compared to solely adhesive interface, due to the integration of long pins. Furthermore, different pin-size-depending failure mechanisms have been detected. The fatigue tests showed, that fabric penetration also improves the fatigue strength significantly by 246 %, whereby the damage mechanisms change in comparison to quasi-static failure

ROI selection for remote photoplethysmography

Camera-based remote photoplethysmography (rPPG) is a technique that can be used to measure vital signs contactlessly. In order to optimize the extraction of photoplethysmographic signals from video sequences, we investigate the spatial dependence of the photoplethysmographic signal. For an evaluation of the suitability of various regions of interest for rPPG measurements, we conducted a study on 20 healthy subjects. We analysed the videos using a refined pulse amplitude mapping approach. Our results show that the signal-to-noise ratio of rPPG signals can be improved by limiting the region of interest to certain regions of the face