Anisotropic Extra Dimensions

We consider the scenario where in a five-dimensional theory, the extra spatial dimension has different scaling than the other four dimensions. We find background maximally symmetric solutions, when the bulk is filled with a cosmological constant and at the same time it has a three-brane embedded in it. These background solutions are reminiscent of Randall-Sundrum warped metrics, with bulk curvature depending on the parameters of the breaking of diffeomorphism invariance. Subsequently, we consider the scalar perturbation sector of the theory and show that it has certain pathologies and the striking feature that in the limit where the diffeomorphism invariance is restored, there remain ghost scalar mode(s) in the spectrum.Comment: 12 pages, no figures, comments and references added, published versio

Διεπαφές Ηλεκτρομυογραφικών Σημάτων για την Αλληλεπίδραση Ανθρώπου Ρομποτικών Συστημάτων σε Δομημένα και Δυναμικά Περιβάλλοντα

173 σ.Σε αυτή την διδακτορική διατριβή επικεντρωνόμαστε σε διεπαφές ηλεκτρομυογραφικών σημάτων οι οποίες μπορούν να χρησιμοποιηθούν για εφαρμογές αλληλεπίδρασης ανθρώπου ρομποτικών συστημάτων, τόσο σε δομημένα όσο και σε δυναμικά περιβάλλοντα. Αρχικά παρουσιάζουμε μια σειρά από προηγμένα σχήματα μηχανικής μάθησης για διεπαφές ηλεκτρομυογραφικών σημάτων, τα οποία συνδυάζουν έναν ταξινομητή με έναν παλινδρομητή, προκειμένου να κατακερματίσουν τον χώρο δράσης του ρομπότ, προσφέροντας καλύτερα αποτελέσματα αποκωδικοποίησης της ανθρώπινης κίνησης με μοντέλα εκπαιδευμένα για συγκεκριμένες διεργασίες. Όσον αφορά τις εφαρμογές αλληλεπίδρασης ανθρώπου ρομπότ, επικεντρωνόμαστε κυρίως στη έννοια και τις διαφορετικές χρήσεις του ανθρωπομορφισμού των ρομποτικών συστημάτων. Αρχικά διακρίνουμε τις διαφορετικές έννοιες του ανθρωπομορφισμού και εισάγουμε την έννοια του λειτουργικού ανθρωπομορφισμού για σχήματα αντιστοίχησης της ανθρώπινης κίνησης σε ανθρωπομορφική ρομποτική κίνηση, τηρώντας παράλληλα συγκεκριμένους περιορισμούς που θέτει ο χρήστης. Στην συνέχεια προτείνουμε μια ολοκληρωμένη μεθοδολογία για την ποσοτικοποίηση του ανθρωπομορφισμού των ρομποτικών χεριών, βασισμένη σε μεθόδους θεωρίας συνόλων και υπολογιστικής γεωμετρίας. Η συγκεκριμένη μεθοδολογία παρέχει ένα κατανοητό μετρικό του ανθρωπομορφισμού το οποίο κυμαίνεται από 0 (μη-ανθρωπομορφικά ρομποτικά συστήματα) σε 1 (ανθρωπομορφικά ρομποτικά συστήματα) και μπορεί να χρησιμοποιηθεί για διαφορετικά είδη ρομπότ. Τέλος, αναπτύσσουμε μια σειρά από ρομποτικά χέρια, ανοιχτού υλικού και κώδικα, τα οποία είναι ελαφριά, χαμηλού κόστους, εύκολα συναρμολογούμενα, υποϋπενεργούμενα και εγγενώς υποχωρητικά. Τα συγκεκριμένα χέρια μπορούν να χρησιμοποιηθούν τόσο για μελέτες ηλεκτρομυογραφικού ελέγχου (ακόμη και για οικονομικά μυοηλεκτρικά προσθετικά χέρια), όσο και για εφαρμογές αλληλεπίδρασης ανθρώπου ρομποτικών συστημάτων (για μελέτες τηλεχειρισμού ρομποτικών συστημάτων βραχίονα – χεριού), για την αρπαγή πληθώρας καθημερινών αντικειμένων σε δυναμικά περιβάλλοντα (ακόμη και υπό συνθήκες αβεβαιότητας σχετικά με τη θέση και το σχήμα των αντικειμένων). Προκειμένου να αποδείξουμε την αποδοτικότητα και λειτουργικότητα των προτεινόμενων μεθοδολογιών, εκτελέσαμε σειρά πειραμάτων με διαφορετικά ρομποτικά συστήματα, τόσο σε δυναμικά όσο και σε δομημένα περιβάλλοντα.In this PhD thesis we focus on EMG based interfaces that can be efficiently used for Human Robot Interaction (HRI) applications in structured and dynamic environments. Initially, we present a series of advanced learning schemes for EMG based interfaces that take advantage of both a classifier and a regressor, in order to split the task-space and provide better human motion estimation accuracy with task specific models. Regarding HRI applications, we mainly focus on anthropomorphism of robot artifacts. At first we distinguish between the different notions of anthropomorphism and we introduce Functional Anthropomorphism for mapping human to anthropomorphic robot motion, respecting at the same time specific human imposed functional constraints. Then we propose a methodology for quantifying anthropomorphism of robot hands, based on set theory and computational geometry methods. This latter methodology concludes to a comprehensive score of anthropomorphism that ranges between 0 (non-humanlike) and 1 (human identical) and can be used for various robot artifacts. Subsequently, we develop a series of open-source, modular, intrinsically-compliant, low-cost, light-weight, underactuated robot hands that can be easily reproduced with off-the-self materials. The proposed hands, efficiently grasp a plethora of everyday life objects, under object pose and/or shape uncertainties and can be used for various HRI applications or even as affordable myoelectric prostheses. In order to prove the efficiency of the proposed methods, we have conducted numerous experiments involving different robot artifacts, operating in both structured and dynamic environments.Μηνάς Β. Λιαροκάπη

Optimized SU-8 processing for low-cost microstructures fabrication without cleanroom facilities

The study and optimization of epoxy-based negative photoresist (SU-8) microstructures through a low-cost process and without the need for cleanroom facility is presented in this paper. It is demonstrated that the Ultraviolet Rays (UV) exposure equipment, commonly used in the Printed Circuit Board (PCB) industry, can replace the more expensive and less available equipment, as the Mask Aligner that has been used in the last 15 years for SU-8 patterning. Moreover, high transparency masks, printed in a photomask, are used, instead of expensive chromium masks. The fabrication of well-defined SU-8 microstructures with aspect ratios more than 20 is successfully demonstrated with those facilities. The viability of using the gray-scale technology in the photomasks for the fabrication of 3D microstructures is also reported. Moreover, SU-8 microstructures for different applications are shown throughout the paper.Work supported by FEDER funds through the Eixo I do Programa Operacional Fatores de Competitividade (POFC) QREN, project reference COMPETE: FCOMP-01-0124-FEDER-020241, and by FCT- Fundação para a Ciência e a Tecnologia, project reference PTDC/EBB-EBI/120334/2010. Vânia C. Pinto thanks the FCT for the SFRH/BD/81526/2011 grant. Paulo J. Sousa thanks the FCT for the SFRH/BD/81562/2011 grant. Vanessa F. Cardoso thanks the FCT for the SFRH/BPD/98109/2013 gran

Exploring new approaches and applications for multi-scale porous UHTCS

The control of processing conditions is key to achieve the desire amount, size and shape of porosity in materials for any application, including extreme applications. However, when particles with irregular shape, large size or differences in surface chemistry are to be used, as it happens for UHTCs, finding the right processing technique becomes crucial to ensure the desired properties, especially when there is not information about the actual performance in the application. This work describes how these challenges were overcome to develop multi-scale porous UHTCs for high temperature insulation as a case study. The exhaustive control of interparticle forces and understanding interaction between additives and powder surfaces resulted in multi-scale highly porous ceramics using different processing routes (replica, sacrificial fillers, particle stabilized foams plus gelcasting, ice templating and partial sintering, (Figure 1)). These colloidal techniques can render the required thermal conductivity across the component with a combination of different tailored porosities. Additionally, large complex-shape components with the same customized porous microstructure were prepared. Please click Additional Files below to see the full abstract

Improving access to and engagement with mental health services among young people from refugee backgrounds: service user and provider perspectives

Limited research has been conducted worldwide on the experiences that children and young people from refugee backgrounds have with mental health services, despite evidence that they have significant vulnerability to the development of mental health problems and to suicidal behaviour and that those with mental ill-health typically underutilise services. The authors were particularly interested in barriers and facilitators to service access and engagement, and conducted two qualitative research projects to improve understanding of the issues – the first with service providers experienced in the refugee area and the second with young refugee service users. The aim of this project was to compare the perspectives of professionals and service users and to identify similarities and differences. The perspectives of the service users and providers were strikingly similar. The analysis identified 21 implications for policy makers, agencies and practitioners, which ranged from issues concerning cultural sensitivity, background matching and mental health literacy to accessibility, setting boundaries and expectations and implementing a holistic and outreach approach. There is a range of specific, practical measures that policy makers and service providers can introduce to enhance access to and engagement with mental health services for young people from refugee backgrounds

Illness causal beliefs in Turkish immigrants

<p>Abstract</p> <p>Background</p> <p>People hold a wide variety of beliefs concerning the causes of illness. Such beliefs vary across cultures and, among immigrants, may be influenced by many factors, including level of acculturation, gender, level of education, and experience of illness and treatment. This study examines illness causal beliefs in Turkish-immigrants in Australia.</p> <p>Methods</p> <p>Causal beliefs about somatic and mental illness were examined in a sample of 444 members of the Turkish population of Melbourne. The socio-demographic characteristics of the sample were broadly similar to those of the Melbourne Turkish community. Five issues were examined: the structure of causal beliefs; the relative frequency of natural, supernatural and metaphysical beliefs; ascription of somatic, mental, or both somatic and mental conditions to the various causes; the correlations of belief types with socio-demographic, modernizing and acculturation variables; and the relationship between causal beliefs and current illness.</p> <p>Results</p> <p>Principal components analysis revealed two broad factors, accounting for 58 percent of the variation in scores on illness belief scales, distinctly interpretable as natural and supernatural beliefs. Second, beliefs in natural causes were more frequent than beliefs in supernatural causes. Third, some causal beliefs were commonly linked to both somatic and mental conditions while others were regarded as more specific to either somatic or mental disorders. Last, there was a range of correlations between endorsement of belief types and factors defining heterogeneity within the community, including with demographic factors, indicators of modernizing and acculturative processes, and the current presence of illness.</p> <p>Conclusion</p> <p>Results supported the classification of causal beliefs proposed by Murdock, Wilson & Frederick, with a division into natural and supernatural causes. While belief in natural causes is more common, belief in supernatural causes persists despite modernizing and acculturative influences. Different types of causal beliefs are held in relation to somatic or mental illness, and a variety of apparently logically incompatible beliefs may be concurrently held. Illness causal beliefs are dynamic and are related to demographic, modernizing, and acculturative factors, and to the current presence of illness. Any assumption of uniformity of illness causal beliefs within a community, even one that is relatively culturally homogeneous, is likely to be misleading. A better understanding of the diversity, and determinants, of illness causal beliefs can be of value in improving our understanding of illness experience, the clinical process, and in developing more effective health services and population health strategies.</p

Perturbations of Gauss-Bonnet Black Strings in Codimension-2 Braneworlds

We derive the Lichnerowicz equation in the presence of the Gauss-Bonnet term. Using the modified Lichnerowicz equation we study the metric perturbations of Gauss-Bonnet black strings in Codimension-2 Braneworlds.Comment: 26 pages, no figures, clarifying comments and one reference added, to be published in JHE