Development of an assistive soft exoskeleton : a multistakeholder endeavour

Background As in other areas, digitalization and new technologies become increasingly relevant for physiotherapy. However, often these developments are driven by technological feasibility rather than by clinical demand. In order to grant maximum acceptability and effective implementation of a technology multiple stakeholders i.e. engineers, patients and therapists need to collaborate throughout the planning and development processes. Here, we describe the design and development of three prototype-generations of a soft and modular exoskeleton. Purpose Development of a soft and modular exoskeleton, which incorporates the needs and requirements of future users. Methods Nine research groups including therapists, designers and engineers from seven European countries were involved in this project. As stakeholders we considered patients with gait limitations due to stroke, incomplete spinal cord injury or age-related weakness (primary end-users, PU), therapists with professional experience in the area of the PU’s conditions and non-professional carers (secondary end-users, SU). The perspectives of PU and SU were incorporated into the technical concepts adopting a user-centered design approach. The initial prototype was designed according to the requirements, which were derived from use-cases representing the target populations. Evaluations of all prototypes were performed using semi-structured interviews with both, PU and SU. Functions of the respective prototypes were evaluated with a predefined testing protocol. The conclusions of the evaluations were fed back to the engineers and informed the development of the consecutive prototypes. All data collection procedures were approved by the local ethics committee and participants provided written informed consent. Results In total eight PU and eight SU were recruited. In general, the prototypes were in an early stage of development and the operation required staff with engineering knowledge and an experimental laboratory. In general, PU and SU rated the technology positively. The individually analyzed data from the interviews and functionality tests revealed heterogeneous results indicating the diversity of the PU’s functional impairments and expectations of PU and SU. Conclusions Based on this project’s experience, we are convinced that future PU and SU of a technology must be involved in the development from the very beginning. However, in order to obtain adequate feedback, the choice of individuals (PU and SU) and the level of involvement must be considered carefully. For example, inadequate expectations may draw the attention to irrelevant issues. In our project, research physiotherapists played a key role by bridging PU and SU with engineers. This information exchange was partially challenging because of different areas of interest, different terminology and geographical distance. Implications A common understanding of the project goals among the project teams and adherence to timelines are essential for successful progress such a large project. The project should assure that all stakeholders can acquire basic knowledge and perspectives of the other involved stakeholders, especially from other disciplines. Specifically for physiotherapists, basic and continuing education should incorporate technological knowledge from engineering disciplines in order to enable physiotherapists to contribute to the development of new devices. This opens the chance to participate in the development of technology for clinical applications. Funding acknowledgements This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 688175 (XoSoft)

Local structure of self-affine sets

The structure of a self-similar set with open set condition does not change under magnification. For self-affine sets the situation is completely different. We consider planar self-affine Cantor sets E of the type studied by Bedford, McMullen, Gatzouras and Lalley, for which the projection onto the horizontal axis is an interval. We show that within small square neighborhoods of almost each point x in E, with respect to many product measures on address space, E is well approximated by product sets of an interval and a Cantor set. Even though E is totally disconnected, the limit sets have the product structure with interval fibres, reminiscent to the view of attractors of chaotic differentiable dynamical systems.Comment: 10 pages, 2 figure

Scattering of Magnetic Edge States

Abstract.: We consider a charged particle following the boundary of a two dimensional domain because a homogeneous magnetic field is applied. We develop the basic scattering theory for the corresponding quantum mechanical edge states. The scattering operator attains a limit for large magnetic fields which preserves Landau bands. We interpret the corresponding scattering phases in terms of classical trajectories. Communicated by Yosi Avro

Urbane Photovoltaikproduktion auf österreichischen Großparkplätzen: ein Beitrag zu nachhaltiger Energieversorgung, zukünftiger Elektromobilität und Bewusstseinsbildung bei Entscheidungsträgern/-innen

Die Photovoltaikbranche erlebte in den vergangenen Jahren stetige Zuwachsraten im zweistelligen Prozentbereich (International Energy Agency 2014; European Photovoltaic Industry 2014). Dennoch stößt der Ausbau der Photovoltaik zunehmend auf Grenzen, da die Nutzung von Photovoltaik zur Energieproduktion viel Platz beansprucht und in Konkurrenz mit traditionellen Nutzungen wie Siedlungswesen, Landwirtschaft, Tourismus, Naturschutz etc. steht, was dazu führt, dass Photovoltaikenergie nur dort produziert werden kann, wo ausreichend Platz verfügbar ist. Dies ist umso zutreffender, je weniger Raum für die verschiedenen Nutzungsansprüche zur Verfügung steht. Für die Photovoltaiknutzung bedeutet dies, dass eine Nutzung auf Flächen mit starkem Nutzungsdruck schwierig ist, es sei denn eine multifunktionale Nutzung ist möglich. Die Eignung ländlicher Freiflächen zur Photovoltaiknutzung ist bereits gut erforscht (Bundesamt für Naturschutz 2012; Bundesamt für Naturschutz und Technische Universität Berlin 2013; Knoll Planung & Beratung 2011; Naturschutzbund Deutschland und BSW-Solar 2005; Stadt Wien 2013). Weit weniger gut ist die Photovoltaiknutzung im Siedlungsgebiet untersucht, da diesen Gebieten, mit Ausnahme horizontaler Dachflächen, ein allgemein zu geringes Potenzial attestiert wird (Hunter und Baldwin 2013; Genske et al. 2009). Hier ist anzumerken, dass vor allem in urbanen Bereichen der Fokus der Potenzialanalysen auf öffentlich verfügbaren Flächen liegt und Potenziale auf privaten Flächen erst gar nicht in die Berechnungen Einzug finden. Eine Flächenkategorie, die derzeit in Österreich kaum im Zusammenhang mit der Photovoltaikproduktion beachtet wird, ist jene der Großparkplätze. Studien geben Auskunft über die Potenziale der vereinzelten Nutzung dieser Flächen (Strauss et al. 2009; Neumann et al. 2012; Tulpule et al. 2013; Chukwu und Mahajan 2014; Serrano-Luján et al. 2015), doch gibt es derzeit keine Übersicht über die Anzahl von möglicherweise geeigneten Parkplätzen in Österreich, noch über die damit verbundene Bedeutung für heimische Photovoltaikunternehmen und die nachhaltige österreichische Stromproduktion. Durch die Mehrfachnutzung der Parkplätze zur Energieerzeugung und zur niederschwelligen Verwendung (Abstellfläche für PKWs), können Synergieeffekte bei ursprünglich konkurrierenden Flächennutzungen erzielt werden. So bedeutet eine mehrdimensionale Nutzung verfügbarer Fläche auch eine Vermeidung von zusätzlicher Flächenversiegelung, die vor allem für Österreich und Europa ein anhaltendes Problem darstellt (Heinrich-Böll-Stiftung et al. 2015). Weiter wird dadurch ein Mehrwert für die Nutzerinnen und Nutzer (z. B. zusätzlicher Komfort durch Beschattung), sowie für Verwalterinnen und Verwalter (z. B. geringere Betriebserhaltungskosten, zusätzliche Einnahmen aus der Energieproduktion, neue Dienstleistungen) der Fläche geschaffen, was zu erhöhter Akzeptanz in siedlungsnahen Gebieten führen kann. Bislang gibt es keinen Überblick über Möglichkeiten einer energieorientierten Bewirtschaftung von Großparkplätzen in Österreich und deren potenziellen Beitrag zur Energiewende und zur Stärkung der heimischen Photovoltaikindustrie. Weiter ist bislang nicht bekannt, für welche Branchen sich durch eine Hebung des Erwartungspotenzials auf Großparkplätzen neue Entwicklungsmöglichkeiten öffnen. Dieses Paper trägt zur Identifikation von zur Energienutzung geegneten Großparkplätzen in Österreich bei. Hierfür wurden sämtliche Großparkplätze (Parkplätze > 600 m²) untersucht und basierend auf Langzeitdaten (klimatologisch, atmospärisch) und aufgrund der räumlich umgebenden Infrastruktur (3D-Gebäude) analysiert

(Machine) Learning from the COVID-19 Lockdown about Electricity Market Performance with a Large Share of Renewables

The negative demand shock due to the COVID-19 lockdown has reduced net demand for electricity -- system demand less amount of energy produced by intermittent renewables, hydroelectric units, and net imports -- that must be served by controllable generation units. Under normal demand conditions, introducing additional renewable generation capacity reduces net demand. Consequently, the lockdown can provide insights about electricity market performance with a large share of renewables. We find that although the lockdown reduced average day-ahead prices in Italy by 45%, re-dispatch costs increased by 73%, both relative to the average of the same magnitude for the same period in previous years. We estimate a deep-learning model using data from 2017--2019 and find that predicted re-dispatch costs during the lockdown period are only 26% higher than the same period in previous years. We argue that the difference between actual and predicted lockdown period re-dispatch costs is the result of increased opportunities for suppliers with controllable units to exercise market power in the re-dispatch market in these persistently low net demand conditions. Our results imply that without grid investments and other technologies to manage low net demand conditions, an increased share of intermittent renewables is likely to increase costs of maintaining a reliable grid

Growth, job matching and unemployment in Austria

In dieser Diplomarbeit werden die Gründe höherer Arbeitslosenraten für Personen mit niedrigerem Bildungsniveau im Vergleich zu besser Ausgebildeten erörtert. Des Weiteren werden die Determinanten, im Speziellen von Wirtschaftswachstum, der beiden unterschiedlichen Arbeitslosenraten beleuchtet. Die Arbeit besteht aus einem theoretischen und einem empirischen Teil. Im theoretischen Teil wird das Model "Growth and Unemployment" von Aghion and Howitt (1994) um Bildungsfaktoren erweitert. Genau genommen werden zwei unterschiedliche Arten von Arbeit eingeführt, das sind zum einen manuelle Arbeit und zum anderen Humankapital. Im empirischen Teil werden unterschiedliche Matching-Funktionen für die beiden Ausbildungsgruppen mittels Panel Daten geschätzt.The intention of my diploma thesis was to determine the causes of persistently higher unemployment rates of people with a lower education level compared to people with a higher one. Furthermore, the determinants of different unemployment rates were of particular interest, especially the impact of economic growth. The thesis consists of two parts – a theoretical and an empirical one. In the theoretical part, the model ”Growth and Unemployment” by Aghion and Howitt (1994) is extended by educational factors, and in the empirical part, skill differentiated matching functions are estimated by using panel data

Accuracy of KinectOne to quantify kinematics of the upper body

Motion analysis systems deliver quantitative information, e.g. on the progress of rehabilitation programs aimed at improving range of motion. Markerless systems are of interest for clinical application because they are low-cost and easy to use. The first generation of the Kinect™ sensor showed promising results in validity assessment compared to an established marker-based system. However, no literature is available on the validity of the new 'Kinect™ for Xbox one' (KinectOne) in tracking upper body motion. Consequently, this study was conducted to analyze the accuracy and reliability of the KinectOne in tracking upper body motion. Twenty subjects performed shoulder abduction in frontal and scapula plane, flexion, external rotation and horizontal flexion in two conditions (sitting and standing). Arm and trunk motion were analyzed using the KinectOne and compared to a marker-based system. Comparisons were made using Bland Altman statistics and Coefficient of Multiple Correlation. On average, differences between systems of 3.9±4.0° and 0.1±3.8° were found for arm and trunk motion, respectively. Correlation was higher for the arm than for the trunk motion. Based on the observed bias, the accuracy of the KinectOne was found to be adequate to measure arm motion in a clinical setting. Although trunk motion showed a very low absolute bias between the two systems, the KinectOne was not able to track small changes over time. Before the KinectOne can find clinical application, further research is required analyzing whether validity can be improved using a customized tracking algorithm or other sensor placement, and to analyze test-retest reliability

Dissecting Supervised Contrastive Learning

Minimizing cross-entropy over the softmax scores of a linear map composed with a high-capacity encoder is arguably the most popular choice for training neural networks on supervised learning tasks. However, recent works show that one can directly optimize the encoder instead, to obtain equally (or even more) discriminative representations via a supervised variant of a contrastive objective. In this work, we address the question whether there are fundamental differences in the sought-for representation geometry in the output space of the encoder at minimal loss. Specifically, we prove, under mild assumptions, that both losses attain their minimum once the representations of each class collapse to the vertices of a regular simplex, inscribed in a hypersphere. We provide empirical evidence that this configuration is attained in practice and that reaching a close-to-optimal state typically indicates good generalization performance. Yet, the two losses show remarkably different optimization behavior. The number of iterations required to perfectly fit to data scales superlinearly with the amount of randomly flipped labels for the supervised contrastive loss. This is in contrast to the approximately linear scaling previously reported for networks trained with cross-entropy.Comment: ICML 2021 camera ready versio