89 research outputs found
Finite Element Modelling of a Deep Excavation in Boston Blue Clay
No full textAbstractThe work investigates the behaviour of a deep excavation that forms part of a wide basement located in Boston, Massachusetts, USA. The glacial marine clay deposit is modelled with a kinematic hardening model for structured soils, its reduced bubble model version and the well-known Modified Cam Clay model. The aim of the work is to assess the effects of the added features of the advanced model, such as small-strain stiffness, structure degradation and anisotropy, on the numerical prediction of the overall behaviour of the excavation. The first part of the paper provides a brief description of the site conditions, ground profile and construction sequences for the case study under consideration. Then, the soil model calibration process using experimental undrained triaxial, self-boring pressuremeter and constant rate of strain consolidation tests is discussed. Finally, the comparison of the predicted wall deflection and ground settlements profiles with observed movements is presented
Κοσμικές ακτίνες στα υψηλότερα ενεργειακά όρια: διερεύνηση νέας αστροφυσικής και φαινομένων αστροσωματιδιακής φυσικής για την ερμηνεία πρόσφατων πειραματικών δεδομένων σύστασης
No full textThis thesis addresses two central and persistent challenges in ultra-high-energy cosmic ray (UHECR) physics: (i) the feasibility of accurate charged-particle backtracking through the Galactic magnetic field (GMF) using sparse yet high-precision local magnetic field measurements, and (ii) the interpretation of UHECR composition data in light of possible new physics in hadronic interactions above center-of-mass energies inaccessible to terrestrial accelerators. In the first part, the work quantifies how the emerging ability to perform local GMF measurements—enabled by modern tomographic polarimetric surveys and Gaia distances—can inform UHECR backtracking. Because such measurements are inherently sparse, the analysis evaluates whether this sparsity limits our capacity to reconstruct UHECR trajectories. Through mock event generation, controlled GMF sampling, and systematic variations of observational uncertainties, the study demonstrates that, provided measurement precision on magnetic-field strength is sufficiently high, even kiloparsec-scale sampling of the GMF can yield meaningful backtracking results at the highest energies. The results also establish lower bounds on achievable accuracy, indicating considerable room for improvement through more sophisticated reconstruction approaches. The second part investigates the longstanding composition problem: the tension between air-shower observables such as X_{\mathrm{max}}, its variance, and the muon counts recorded at ground-based observatories. Using CORSIKA simulations with state-of-the-art hadronic interaction models (EPOS-LHC, QGSJETII-04) and extending prior analytic work (PT19), the thesis explores whether modified proton–air interactions above a threshold energy could mimic the observational signatures of a heavier composition while retaining a physically natural light-composition scenario. The simulations show that increased first-collision multiplicity, combined with an enhanced proton–air cross-section, can reproduce the observed behaviour of both \langle X_{\mathrm{max}} \rangle and \sigma(X_{\mathrm{max}}). Although the muon excess problem is alleviated, it is not entirely resolved, indicating that additional model ingredients—such as altered meson production ratios—may be required. Overall, this work provides quantitative assessments that clarify key limitations and opportunities in UHECR astrophysics. It demonstrates that forthcoming GMF measurements can materially improve backtracking prospects and shows how phenomenological extensions of hadronic physics at super-LHC energies may account for composition observables without invoking astrophysically contrived source scenarios.Η διατριβή εξετάζει δύο καίρια ζητήματα στη φυσική των υπερ-υψηλής ενέργειας κοσμικών ακτίνων (UHECR): (i) τη δυνατότητα ακριβούς οπισθοϊχνηλάτησης φορτισμένων σωματιδίων μέσα από το Γαλαξιακό Μαγνητικό Πεδίο (GMF) χρησιμοποιώντας αραιές αλλά υψηλής ακρίβειας τοπικές μετρήσεις, και (ii) την ερμηνεία των πειραματικών δεδομένων σύστασης υπό το πρίσμα πιθανής νέας φυσικής σε αλληλεπιδράσεις πρωτονίου-αέρα πέρα από τα ενεργειακά όρια των επιταχυντών. Στο πρώτο μέρος, διερευνάται συστηματικά κατά πόσο η εγγενής αραιότητα των μετρήσεων του GMF –παρότι ακριβείς– περιορίζει την αποκατάσταση των τροχιών UHECR. Με χρήση ελεγχόμενων προσομοιώσεων, τεχνητών γεγονότων και ρεαλιστικών σεναρίων μέτρησης, αποδεικνύεται ότι, εφόσον η αβεβαιότητα στην ένταση του μαγνητικού πεδίου παραμείνει χαμηλή, ακόμη και αραιή δειγματοληψία σε κλίμακες της τάξης kiloparsec μπορεί να προσφέρει χρήσιμη οπισθοϊχνηλάτηση για τα υψηλότερα ενεργειακά γεγονότα. Παρέχεται επίσης ελάχιστο όριο επίδοσης, υποδεικνύοντας ότι βελτιωμένες τεχνικές αναδόμησης μπορούν να ενισχύσουν περαιτέρω την ακρίβεια. Στο δεύτερο μέρος, η διατριβή αντιμετωπίζει το επίμονο «πρόβλημα σύστασης» των UHECR: την ασυμφωνία μεταξύ παρατηρήσεων της μέγιστης βάθους ανάπτυξης X_{\mathrm{max}}, της διακύμανσής του και του πλήθους μιονίων που ανιχνεύονται στο έδαφος. Με χρήση προσομοιώσεων CORSIKA και επεκτείνοντας προηγούμενη αναλυτική δουλειά (PT19), εξετάζεται εάν τροποποιημένες αλληλεπιδράσεις πρωτονίου-αέρα πάνω από μια κατώφλια ενέργειας μπορούν να αναπαράγουν τις παρατηρήσεις χωρίς την ανάγκη βαριάς αρχικής σύστασης. Τα αποτελέσματα δείχνουν ότι αυξημένη πολλαπλότητα προϊόντων της πρώτης σύγκρουσης και ενισχυμένη ενεργό διατομή μπορούν να περιγράψουν τόσο το \langle X_{\mathrm{max}} \rangle όσο και το \sigma(X_{\mathrm{max}}). Παρά την βελτίωση στο πρόβλημα «πλεονάζοντος πλήθους μιονίων», αυτό δεν εξαλείφεται πλήρως, υποδηλώνοντας ότι απαιτούνται πρόσθετες τροποποιήσεις στα μοντέλα της πρώτης σύγκρουσης. Συνολικά, η διατριβή συνεισφέρει ουσιαστικά στη διαμόρφωση του θεωρητικού και παρατηρησιακού πλαισίου των UHECR. Τεκμηριώνει ότι οι αναδυόμενες τεχνικές τοπικής χαρτογράφησης του GMF μπορούν να ενισχύσουν σημαντικά τις δυνατότητες οπισθοϊχνηλάτησης και επιδεικνύει πως φαινομενολογικές επεκτάσεις της αδρονικής φυσικής σε υπερ-LHC ενέργειες μπορεί να εξηγήσουν τις σύγχρονες μετρήσεις σύστασης
Cosmological screening and the phantom braneworld model
No full textAbstract The scalar and vector cosmological perturbations at all length scales of our Universe are studied in the framework of the phantom braneworld model. The model is characterized by the parameter ΩM≡M3/2m2H0 , with M and m the five- and four-dimensional Planck scales, respectively, and H0 the Hubble parameter today, while ΩM→0 recovers the ΛCDM model. Ignoring the backreaction due to the peculiar velocities and also the bulk cosmological constant, allows the explicit computation of the gravitational potentials, Φ and Ψ . They exhibit exponentially decreasing screening behaviour characterized by a screening length which is a function of the quasidensity parameter ΩM
The H3 Haplotype of the EPCR Gene Determines High sEPCR Levels in Critically-ill Septic Patients
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Web Based Learning and Off-the-shelf Software: towards a Typology of VLE Interfaces
No full textThis paper: - attempts a classification of Web-based Virtual Learning Environments (VLEs). Criteria for this classification are the content, computer mediated communication and collaboration, how the VLE supports the tasks that course developers/educators have to carry out in setting up a course and how it attempts to provide a student centred, rather than a teacher centred, learning environment. - focuses on three commercially developed VLEs which the author has had experience with as educator and developer/implementer: Lotus LearningSpace, WebCT and FirstClass. It draws from the comparison of the interface of the three to build a typology of VLE interfaces. - touches on instructional design and HCI issues and looks at guidelines and issues to consider when designing VLE interfaces. It is claimed that there are aspects of interface design that enhance interactivity and help students to manage the complexity of VLEs. It points towards the use of flexible and customisable interfaces where the educator can determine those functions and features that enhance the learner experience.Proceedings of the 7th International Conference of European University Information Systems, EUNIS2001, 28.03.2001 - 30.03.2001, Humboldt-Universität zu Berlin, pp 48-5
The Struggle for Representation: An Architect inside Mark Z. Danielewski’s House of Leaves
No full textThis book presents some of these manifold forms. It opens with a short journey into some of the most significant literary spaces and imaginary constructions by writer Alberto Manguel, followed by Arch. Colin Fournier's digression on architectural and urban fictions, its practices and experiences that shaped our contemporaneity. Next is the core of this book, a collection of articles sough to bring together a diversity of individuals, discourses and practices to examine the role of fiction and imagination in architecture and related disciplines, organized into eight thematic chapters, each introduced by a guest author. Ranging widely from history to literary analysis, cinema, graphic, urban, conceptual and literary experiments, the different contributions are, however, highly porous - as the reader will discover - and together they engender new ground for thought and exploration.
Few publications and books deal specifically with architecture from an interdisciplinary perspective, especially from the 'fiction angle'. The editorial scope outlined in this book intends to be perceptive and distinctive. It aims at serving scholars, architects, designers, authors, students and a wider, non-professional audience. It is a contribution to the field and pushes forward research in architectural practice and thought in intriguing and exciting directions, precisely in this moment, in which one may question architecture's inclination to become a pseudo-technical service or mere signature shape-giving; in which one may question urban planning's propensity to produce social failure, one may as well ask if the imagination of fiction is not the ultimate gizmo with which to face a reality that has gone... stranger than fiction
Breast Cancer Response Prediction in Neoadjuvant Chemotherapy Treatment Based on Texture Analysis
No full textAbstractMRI modality is one of the most usual techniques used for diagnosis and treatment planning of breast cancer. The aim of this study is to prove that texture based feature techniques such as co-occurrence matrix features extracted from MRI images can be used to quantify response of tumor treatment. To this aim, we use a dataset composed of two breast MRI examinations for 9 patients. Three of them were responders and six non responders. The first exam was achieved before the initiation of the treatment (baseline). The later one was done after the first cycle of the chemo treatment (control). A set of selected texture parameters have been selected and calculated for each exam. These selected parameters are: Cluster Shade, dissimilarity, entropy, homogeneity. The p-values estimated for the pathologic complete responders pCR and non pathologic complete responders pNCR patients prove that homogeneity (P-value=0.027) and cluster shade (P-value=0.0013) are the more relevant parameters related to pathologic complete responders pCR
Yeast Biofilm as a Bridge between Medical and Environmental Microbiology Across Different Detection Techniques
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Author Correction: Momentum informed muon scattering tomography for monitoring spent nuclear fuels in dry storage cask
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