122 research outputs found
Ultra-fast escape of a deformable jet-propelled body
No full textIn this work a cephalopod-like deformable body that fills an internal cavity with fluid and expels it to propel an escape manoeuvre, while undergoing a drastic external shape change through shrinking, is shown to employ viscous as well as mainly inviscid hydrodynamic mechanisms to power an impressively fast start. First, we show that recovery of added-mass energy enables a shrinking rocket in a dense inviscid flow to achieve greater escape speed than an identical rocket in a vacuum. Next, we extend the shrinking body results of Weymouth & Triantafyllou (J. Fluid Mech., vol. 702, 2012, pp. 470–487) to three-dimensional bodies and show that three hydrodynamic mechanisms must be combined to achieve rapid escape performance in a viscous fluid: added-mass energy recovery; flow separation elimination; and an optimized energy storage and recovery. In particular, we show that the mechanism of separation elimination achieved through rapid body shrinking, coordinated with the mechanism of recovering the initially imparted added-mass energy, is critical to achieving a high escape speed. Hence a flexible, collapsing body can be vastly superior to a rigid-shell jet-propelled body
Vortical patterns behind a tapered cylinder
No full textThesis (M.S.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering; and the Woods Hole Oceanographic Institution), 1998.Includes bibliographical references (p. 85-91).by Alexandra Hughes Techet.M.S
Erratum: Corrigendum to “Esophageal remnant cancer 35 years after acidic caustic injury: A case report” (International Journal of Surgery Case Reports (2016) 25 (215–217) (S2210261216302358) (10.1016/j.ijscr.2016.06.051))
No full textThe authors regret to change the first name of the second author; more specifically we would like to change the first name “Stamatina” to “Tania”—the family name (“Triantafyllou”) remains as it is. On behalf of all the authors, I assure that we are in agreement with this change. The authors would like to apologise for any inconvenience caused. © 2016 The Author(s
Through-the-needle biopsy of pancreatic cystic lesions: current evidence and implications for clinical practice
No full textIntroduction: : There is increasing evidence to support the efficacy of endoscopic ultrasound (EUS)-guided through-the-needle biopsy (TTNB) technique as a means of sampling pancreatic cystic lesions (PCLs). Results provide evidence demonstrating the benefits of this procedure over standard EUS fine-needle aspiration (FNA), thus supporting a push for its widespread implementation in clinical practice. Though this technique has demonstrated advantages, achieving these advantages in clinical practice is contingent upon careful considerations to ensure safety and efficacy. Areas covered: : The purpose of this review is to assess the level of evidence supporting the use of through-the-needle biopsy, revise its main technical and procedural characteristics, and to develop suggested guidelines outlining the safe assimilation of this device in clinical practice. Expert opinion: : EUS-TTNB enables more definitive and accurate diagnosis of PCLs by providing higher quality histological samples. However, EUS-TTNB is not appropriate for all PCLs. Selection of suitable patients as well as morphology and risk factors of the cystic lesion is a crucial component of achieving the described benefits of this procedure while minimizing risks of adverse effects. Subjects with weak or absent indications for this procedure are susceptible to a range of complications and may even result in fatality
Isovist Fingerprinting as new way of Indoor Localisation
No full textNowadays, humans rely in technology more and more when it comes to navigation and localisation and in many aspects of life as well. While most concepts related to localisation and navigation of outdoors environments are already well derived from various researches and softwares, the indoor environment remains a significantly unexplored area. Nevertheless, lately there have been increased interest on Location Based Services (LBS) and Indoor Positioning Systems (IPS). There are already several methods available for indoor localisation such as Wi-Fi Fingerprinting and Bluetooth Beacons, but none of them is fully functional yet. It remains a field that requires more and further research and investigation in order to reach a satisfactory and complete Indoor Localisation-Navigation method. Therefore, this thesis's main objective is to investigate and explore a new method for Indoor Localisation based on Isovists. The exploration and evaluation of Isovist-Fingerprinting approach for Indoor Localisation can extend the fields of LBS and Geomatics. The main research question is “To what extent can isovist support Indoor Localisation” and through this and a series of sub-questions to analyse the Isovist concept in relation to the Indoor Localisation. This is achieved by forming a proof of concept and a methodology that investigates how the Isovists would benefit an LBS.To succeed that the methodology is divided into 4 main sections. The Data Acquisition for which the newly supported from smartphones Light Detection And Ranging (LiDAR) technology were used. The Space Syntax and Isovist Analysis Measures, where all the concepts related such as the Isovist Parameters were analysed in depth for better understanding of their effect. Then the Matching and Localisation Algorithms, where the possibilities and options on how to reach the localisation were investigated and analysed. And finally, the Tests and Experiments took place in order to evaluate all the prior stages of the methodology.The main conclusion of this research is that a method for Indoor Localisation based on Isovists is feasible and can indeed support an LBS. The analysis and evaluation of all related components has be done and if putting all the parts in the right order they can be of high value for LBS applications. Since is a new method of Indoor Localisation, there is plenty of future work to be done which mainly focuses on how to connect it with existing techniques and integrate all together into a user application.Geomatic
Ψυχοδυναμικά και ψυχοπαθολογικά χαρακτηριστικά υποτύπων της Οριακής Διαταραχής Προσωπικότητας: συστηματική ανασκόπηση ερευνών και ανάλυση λανθάνοντος προφίλ
No full textΗ οριακή διαταραχή προσωπικότητας (ΟΔΠ), από τα πρώτα χρόνια εμφάνισης του όρου, έως και σήμερα, που η διάγνωσή της εδράζεται στα στενά καθορισμένα κριτήρια του DSM, βρίσκεται διαρκώς σε μια προσπάθεια ορισμού, επανακαθορισμού, και διερεύνησης της ετερογένειας που χαρακτηρίζει τόσο τα συμπτώματα, όσο και τα άτομα που φέρουν τη διαταραχή. Mε σκοπό τη μεγαλύτερη κατανόηση της ετερογένειας της ΟΔΠ όπως έχει μελετηθεί ως σήμερα, διενεργήθηκαν δύο συστηματικές ανασκοπήσεις, με σκοπό τον εντοπισμό και τη συγκριτική αξιολόγηση των ευρημάτων, των μελετών που διερεύνησαν τη δομή των κριτηρίων της ΟΔΠ κατά DSM, με τη χρήση μεθόδων παραγοντικής ανάλυσης (έρευνα εστιασμένη στις μεταβλητές), και των μελετών που διερεύνησαν την ύπαρξη υποτύπων της ΟΔΠ, με τη χρήση μεθόδων ανάλυσης συστάδων (έρευνα εστιασμένη στα άτομα). Όσον αφορά τις υποκείμενες διαστάσεις της ΟΔΠ, τα συγκριτικά αποτελέσματα επιβεβαιώνουν τόσο τη μονοπαραγοντική δομή της ΟΔΠ, όσο και μία δομή τριών παραγόντων (διαταραγμένες σχέσεις, συμπεριφορική απορρύθμιση και συναισθηματική απορρύθμιση). Οι έρευνες που μελέτησαν υποτύπους της ΟΔΠ, εστίασαν σε προεξέχοντα χαρακτηριστικά της διαταραχής, και φαίνεται να επιβεβαιώνουν τις θεωρητικές παρατηρήσεις ύπαρξης ενός εσωτερικευτικού και ενός εξωτερικευτικού υποτύπου της ΟΔΠ, αλλά και την ύπαρξη περισσότερο και λιγότερο επιβαρυμένων υποτύπων της διαταραχής. Με σκοπό τη διερεύνηση της ύπαρξης υποτύπων σε ελληνικό πληθυσμό, πραγματοποιήθηκε ανάλυση λανθάνοντος προφίλ, με βάση τα διαστασιακά χαρακτηριστικά διαταραχών προσωπικότητας σε άτομα με ΟΔΠ που παρακολουθούνταν στα ειδικά ιατρεία του Αιγινητείου, Αττικού, και Σισμανογλείου νοσοκομείου (Ν=160). Με συμφωνία των δεικτών AIC, BIC, CAIC, SABIC και BLRT, επιλέχθηκε ένα μοντέλο πέντε προφίλ, τα οποία ονομάστηκαν Αμιγώς οριακός, Εξωστρεφής, Ανασφαλής, Σοβαρά επιβαρυμένος και Εκκεντρικός υποτύπος. Οι υποτύποι στη συνέχεια συγκρίθηκαν ως προς τα ψυχοδυναμικά και ψυχοπαθολογικά χαρακτηριστικά τους μέσω παραμετρικών ή μη-παραμετρικών ANOVA, και post-hoc αναλύσεων κατά ζεύγη. Τα αποτελέσματα υποδεικνύουν ότι ο Αμιγώς οριακός υποτύπος (n=37), εμφανίζει λίγα χαρακτηριστικά άλλων διαταραχών προσωπικότητας, ηπιότερη ψυχοπαθολογία, και είναι καλύτερα συγκροτημένος σε ψυχοδυναμικό επίπεδο. Στον αντίποδα, ο Σοβαρά επιβαρυμένος υποτύπος (n=27), καταγράφει υψηλές τιμές στις περισσότερες διαταραχές προσωπικότητας, φέρει περισσότερα ψυχοπαθολογικά συμπτώματα και βαρύτερη ΟΔΠ, ενώ παράλληλα εμφανίζει περισσότερες ανώριμες άμυνες, υψηλότερη αβεβαιότητα στην αναστοχαστική λειτουργία και επιβαρυμένη διαπροσωπική λειτουργικότητα. Ο Εξωστρεφής υποτύπος (n=33), χαρακτηρίζεται από ιστριονικά και ναρκισσιστικά στοιχεία, φέρει συγκριτικά ηπιότερη ψυχοπαθολογία, ωστόσο εμφανίζει υψηλή χρήση ανώριμων αμυνών κι ένα διαπροσωπικό προφίλ που δομείται στη διάσταση της κυριαρχίας. Ο Ανασφαλής υποτύπος (n=27), χαρακτηρίζεται κυρίως από αποφευκτικά και εξαρτητικά στοιχεία, εμφανίζοντας συγκριτικά μεγαλύτερα ποσοστά κατάθλιψης, φοβίας και διαπροσωπικής ευαισθησίας. Η αμυντική του λειτουργία είναι σχετικά δομημένη, ωστόσο εμφανίζει περισσότερα διαπροσωπικά προβλήματα, στις διαστάσεις της υπέρμετρης ενδοτικότητας, της έλλειψης πρωτοβουλίας και της κοινωνικής συστολής. Ο Εκκεντρικός υποτύπος (n=36), φέρει συγκριτικά περισσότερα παρανοειδή και σχιζότυπα, και χαμηλότερα εξαρτητικά στοιχεία, και εμφανίζει μέση λειτουργία της προσωπικότητας, με σχετικά υψηλή ψυχοπαθολογική επιβάρυνση. Η έρευνα υποτύπων της ΟΔΠ, αναμένεται να διευρύνει την κατανόηση των κλινικών για τη διαταραχή, και να συνεισφέρει στην εξατομικευμένη αντιμετώπιση των ασθενών.Borderline personality disorder (BPD), from its first appearance as a psychoanalytic or a psychiatric construct, and up to the current understanding of the disorder within the well-circumscibed boundaries of the DSM diagnosis, continues to be the subject of re-definition and exploration of the marked heterogeneity that underlies the symptoms and separates the individuals with the disorder. To further the understanding of BPD heterogeneity, two systematic reviews were conducted to identify and critically appraise studies that either investigated the structure of BPD criteria, using factor analytic methods, or the possible existence of BPD subtypes, using cluster analytic methods. In terms of the underlying BPD dimensions, the comparative results provide support for both the unidimensional and a three-dimensional structure of the DSM criteria, the latter consisting of the Disturbed relationships, Emotional dysregulation, and Behavioral dysregulation dimensions. Studies examining BPD subtypes, have focused on salient features of the disorder, and appear to confirm the theoretical observations regarding the existence of an internalizing and an externalizing BPD subtype, as well as the existence of more adaptive and more disruptive subtypes of the disorder. With the aim of exploring the possible existence of BPD subtypes in a Greek adult population, a latent profile analysis based on the dimensional characteristics of personality disorders, was conducted in outpatients with a BPD diagnosis, being treated at the Aiginiteio, Attiko, and Sismanogleio Hospital (N=160). AIC, BIC, CAIC, SABIC and BLRT values favoured a five-profile model, with the profiles named Pure borderline, Externalizing, Insecure, Severely burdened and Eccentric subtype. The subtypes were then compared on psychopathological and psychodynamic variables using parametric or non-parametric ANOVAS, followed by post-hoc pairwise analyses. The Pure borderline subtype (n=37), displays fewer traits of other personality disorders, experiences less psychopathology and appears to be better adjusted on a psychodynamic level. On the other hand, the Severely burdened subtype (n=27), displays a variety of other personality disorder traits, comparatively more psychopathology, including severe BPD symptoms, uses more immature defenses, faces more interpersonal problems and is characterized by greater reflective functioning uncertainty. The Externalizing subtype (n=33), is characterized by more histrionic and narcissistic features, experiences comparatively less psychopathology, uses more immature defenses and has a dominant interpersonal profile. The Insecure subtype (n=27), shows more avoidant and dependent characteristics, while experiencing comparatively more depressive and phobic symptoms. While its defense structure is relatively neurotic, the Insecure subtype experiences more interpersonal problems, being overly accommodating, non-assertive and socially inhibited. The Eccentric subtype (n=36), exhibits more paranoid and schizotypal traits, less dependent traits, and is placed in-between the more and less adapted subtypes in terms of personality organization, while experiencing relatively more psychopathology. Studies exploring BPD subtypes, are expected to broaden the clinicians’ perceptions of the disorder, and contribute to the individualized treatment of people with BPD
Correction to: Agent‑based models of human response to natural hazards: systematic review of tsunami evacuation (Natural Hazards, (2023), 115, 3, (1887-1908), 10.1007/s11069-022-05643-x)
No full textThe article “Agent-based models of human response to natural hazards: systematic review of tsunami evacuation”, written by Karel Mls · Milan Kořínek · Kamila Štekerová · Petr Tučník ·Vladimír Bureš · Pavel Čech · Martina Husáková · Peter Mikulecký ·Tomáš Nacházel · Daniela Ponce · Marek Zanker · František Babič ·Ioanna Triantafyllou., was originally published Online First without Open Access. After publication in volume 115, issue 3, page 1887–1908 the authors decided to opt for Open Choice and to make the article an Open Access publication. Therefore, the copyright of the article has been changed to © The Author(s) 2023 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit. The original article has been corrected. © 2023, Springer Nature B.V
Experimental visualization of the near-boundary hydrodynamics about fish-like swimming bodies
No full textThesis (Ph. D.)--Joint Program in Applied Ocean Physics and Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering and the Woods Hole Oceanographic Institution), 2001.Includes bibliographical references (leaves 149-155).This thesis takes a look at the near boundary flow about fish-like swimming bodies. Experiments were performed up to Reynolds number 106 using laser Doppler velocimetry and particle imaging techniques. The turbulence in the boundary layer of a waving mat and swimming robotic fish were investigated. How the undulating motion of the boundary controls both the turbulence production and the boundary layer development is of great interest. Unsteady motions have been shown effective in controlling flow. Tokumaru and Dimotakis (1991) demonstrated the control of vortex shedding, and thus the drag on a bluff body, through rotary oscillation of the body at certain frequencies. Similar results of flow control have been seen in fish-like swimming motions. Taneda and Tomonari (1974) illustrated that, for phase speeds greater than free stream velocity, traveling wave motion of a boundary tends to retard separation and reduce near-wall turbulence. In order to perform experiments on a two-dimensional waving plate, an apparatus was designed to be used in the MIT Propeller tunnel, a recirculating water tunnel. It is an eight-link piston driven mechanism that is attached to a neoprene mat in order to create a traveling wave motion down the mat. A correlation between this problem and that of a swimming fish is addressed herein, using visualization results obtained from a study of the MIT RoboTuna. The study of the MIT RoboTuna and a two-dimensional representation of the backbone of the robotic swimming fish was performed to further asses the implications of such motion on drag reduction. PIV experiments with the MIT RoboTuna indicate a laminarisation of the near boundary flow for swimming cases compared with non-swimming cases along the robot body. Laser Doppler Velocimetry (LDV) and PIV experiments were performed.(cont.) LDV results show the reduction of turbulence intensity, near the waving boundary, for increasing phase speed up to 1.2 m/s after which the intensities begin to increase again through Cp = 2.0 where numerical simulations by Zhang (2000) showed separation reappearing on the back of the crests. Velocity profiles who an acceleration of the fluid beyond the inflow speed at the crest region increases with increased phase speed and no separation was present in the trough for the moving wall. The experimental techniques used are also discussed as they are applied in these experiments.by Alexandra Hughes Techet.Ph.D
Indoor localisation through Isovist fingerprinting from point clouds and floor plans
No full textThe objective of this paper is to investigate and propose a method for Indoor Localisation based on Isovists, with the aim of extending the fields of Location-based Services and Geomatics. Various methods and combinations incorporating Isovist concepts, Space Syntax, and visibility graphs are examined and assessed. By investigating these approaches, this study aims to create a comprehensive methodology to achieve localisation using Isovists. The main conclusion drawn from this research is that an Indoor Localisation method based on Isovists is not only feasible but can also effectively support Location-based Services. The analysis and evaluation of all the components have been thoroughly conducted, indicating that when properly integrated, they can provide substantial value for LBS applications. As this is a new method for Indoor Localisation, there is significant scope for future work, particularly in terms of connecting it with existing techniques and integrating them into user applications.Digital Technologie
Influence of wing kinematics on aerodynamic performance in hovering insect flight
No full textThe influence of different wing kinematic models on the aerodynamic performance of a hovering insect is investigated by means of two-dimensional time-dependent Navier–Stokes simulations. For this, simplified models are compared with averaged representations of the hovering fruit fly wing kinematics. With increasing complexity, a harmonic model, a Robofly model and two more-realistic fruit fly models are considered, all dynamically scaled at Re = 110. To facilitate the comparison, the parameters of the models were selected such that their mean quasi-steady lift coefficients were matched. Details of the vortex dynamics, as well as the resulting lift and drag forces, were studied. The simulation results reveal that the fruit fly wing kinematics result in forces that differ significantly from those resulting from the simplified wing kinematic models. In addition, light is shed on the effect of different characteristic features of the insect wing motion. The angle of attack variation used by fruit flies increases aerodynamic performance, whereas the deviation is probably used for levelling the forces over the cycle.Aerospace Design, Integration and OperationsAerospace Engineerin
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