UNDERSTANDING THE PHYSICS OF KAPPA (Κ0): INSIGHTS FROM THE EUROSEISTEST NETWORK

Στην παρούσα μελέτη υπολογίζουμε την παράμετρο απόσβεσης στις υψηλές συχνότητες, κ0, για το δίκτυο EUROSEISTEST. Οι εδαφικές συνθήκες στους 14 επιφανειακούς και 6 υπόγειους επιταχυνσιογράφους κυμαίνονται από μαλακές αποθέσεις έως σκληρό βράχο. Πρώτα διαχωρίζουμε την τοπική από την περιφερειακή απόσβεση και υπολογίζουμε το κ0. Έπειτα, χρησιμοποιούμε την υπάρχουσα γνώση του εδαφικού προφίλ και των δυναμικών εδαφικών ιδιοτήτων για να συσχετίσουμε το κ0 με διάφορες γεωτεχνικές παραμέτρους (Vs30, συχνότητα συντονισμού, βάθος έως το βραχώδες υπόβαθρο). Τέλος, χρησιμοποιούμε τα αποτελέσματά μας για να βελτιώσουμε τη φυσική κατανόηση του κ0. Προτείνουμε ένα μοντέλο που περιλαμβάνει δύο καινοτόμες ιδέες. Αφ’ ενός, παρατηρούμε πως οι τιμές του κ0 σταθεροποιούνται για υψηλές τιμές Vs, κάτι που πιθανώς σημαίνει πως οι τιμές κ0 συγκλίνουν ανά περιοχή για σκληρό βράχο. Σε αυτήν την περίπτωση, προτείνουμε τη χρήση δεδομένων από όργανα εντός γεωτρήσεων για τον υπολογισμό τους. Αφ’ ετέρου, παρατηρούμε πως η εδαφική απόσβεση δεν επαρκεί για να περιγράψει τη συνολική μετρηθείσα απόσβεση. Προτείνουμε την ύπαρξη μιας επιπλέον πηγής απόσβεσης πέραν της εδαφικής: την απόσβεση διασποράς που οφείλεται στις μικρής κλίμακας ετερογένειες του εδαφικού προφίλ. Σε αυτήν την περίπτωση, οι γεωτεχνικές μετρήσεις της απόσβεσης των υλικών ενδέχεται να μην επαρκούν για την εκτίμηση της συνολικής τοπικής απόσβεσης. Ξεκινώντας όμως από μια εκτίμηση της απόσβεσης της περιοχής (από γεώτρηση), και προσθέτοντας την απόσβεση του υλικού, μπορεί κανείς να προσδιορίσει μία ελάχιστη τιμή για το κ0.this study we estimate the spectral decay factor κ0 for the EUROSEISTEST array. Site conditions range from soft sediments to hard rock over 14 surface and 6 downhole accelerographs. First, we separate local and regional high frequency attenuation and measure κ0. Second, we use the existing knowledge of the geological profile and material properties to correlate κ0 with different site characterisation parameters (Vs30, resonant frequency, depth-to-bedrock). Third, we use our results to improve our physical understanding of κ0. We propose a conceptual model comprising two new notions. On the one hand, we observe that κ0 stabilises for high Vs values; this may indicate the existence of regional values for hard rock κ0. If so, we propose that borehole measurements may be useful in determining them. On the other hand, we find that material damping may not suffice to account for the total measured attenuation. We propose that, apart from damping, additional site attenuation may be caused by scattering from small-scale profile variability. If this is so, then geotechnical damping measurements may not suffice to infer overall crustal attenuation under a site; but starting with a regional (borehole) value and adding damping, we might define a lower bound for site-specific κ0

Entrainment of randomly coupled oscillator networks by a pacemaker

Entrainment by a pacemaker, representing an element with a higher frequency, is numerically investigated for several classes of random networks which consist of identical phase oscillators. We find that the entrainment frequency window of a network decreases exponentially with its depth, defined as the mean forward distance of the elements from the pacemaker. Effectively, only shallow networks can thus exhibit frequency-locking to the pacemaker. The exponential dependence is also derived analytically as an approximation for large random asymmetric networks.Comment: 4 pages, 3 figures, revtex 4, submitted to Phys. Rev. Let

Re-positioning SoTL toward the T-shaped Community

Amongst a range of changes that have taken place within tertiary education, perhaps the most revolutionary has been a shift to student-centred approaches focused on life-long learning. Accompanying this approach to holistic higher education (HE) has been a growing interest in, and understanding of, the Scholarship of Teaching and Learning (SoTL). SoTL has, at its core, a deep concern with student learning and is therefore well-aligned with higher education’s renewed focus on its students. In this conceptual paper, we examine the impact of the T-shaped person which many tertiary institutions are operationalizing to inform and connect the development of students’ deep disciplinary knowledge with non-academic and employment readiness skills (such as communication, problem-solving, teamwork, and critical thinking). Importantly, we argue for a re-positioning of SoTL to complement and support this model, with SoTL as both the fulcrum and the fluid, multiple threads of discourse that are intricately entwined around the structure of the T-shaped model. We encourage our colleagues to strive to be T-shaped practitioners and we cast a vision of a T-shaped community. Here, all stakeholders within HE connect both their academic knowledge and holistic skills in collaborative ways to produce learners who flourish in modern society. The SoTL community plays a pivotal role in achieving this vision and is well-positioned to expand the current notion of SoTL toward a more holistic, interconnected, central role in HE

Statistical modeling of ground motion relations for seismic hazard analysis

We introduce a new approach for ground motion relations (GMR) in the probabilistic seismic hazard analysis (PSHA), being influenced by the extreme value theory of mathematical statistics. Therein, we understand a GMR as a random function. We derive mathematically the principle of area-equivalence; wherein two alternative GMRs have an equivalent influence on the hazard if these GMRs have equivalent area functions. This includes local biases. An interpretation of the difference between these GMRs (an actual and a modeled one) as a random component leads to a general overestimation of residual variance and hazard. Beside this, we discuss important aspects of classical approaches and discover discrepancies with the state of the art of stochastics and statistics (model selection and significance, test of distribution assumptions, extreme value statistics). We criticize especially the assumption of logarithmic normally distributed residuals of maxima like the peak ground acceleration (PGA). The natural distribution of its individual random component (equivalent to exp(epsilon_0) of Joyner and Boore 1993) is the generalized extreme value. We show by numerical researches that the actual distribution can be hidden and a wrong distribution assumption can influence the PSHA negatively as the negligence of area equivalence does. Finally, we suggest an estimation concept for GMRs of PSHA with a regression-free variance estimation of the individual random component. We demonstrate the advantages of event-specific GMRs by analyzing data sets from the PEER strong motion database and estimate event-specific GMRs. Therein, the majority of the best models base on an anisotropic point source approach. The residual variance of logarithmized PGA is significantly smaller than in previous models. We validate the estimations for the event with the largest sample by empirical area functions. etc

Books

Current Ocular Therapy. Ed. by F. T. Fraunfelder, F. Hampton Roy and S. Martha Meyer. Pp. xiii + 792. Illustrated. £55. Nonhmead: WB Saunders. 1989.Dysfunctional Uterine Bleeding and Menorrhagia. Bailliere's Clinical Obstetrics and Gynaecolcgy: International Practice and Research, June 1989. Ed. by J. O. Drife. Pp. 217 + 428. Illustrated. £18,50. Northmead: WE Saunders.1989.Treatment of Cancer. 2nd ed. Ed. by Karol Sikora and Keith E. Halnan. Pp. ix + 916. Illustrated. Price £99,50. London: Chapman and Hall Medical. 1990.Ocular Syndromes and Systemic Diseases. 2nd edition. Ed. by F. Hampton Roy. Pp. xlvii + 470. £40. Northmead: WE Saunders. 1989.Non-invasive Cardiac Imaging. British Medical Bulletin. Vol. 45, No. 4. Ed. by D. G. Gibson. Pp. 830 + 1109. Illustrated. £25 (UK) or £31,50 (overseas). New York: Churchill Livingstone. 1989.Laparoscopic Surgery. Bailliere's Clinical Obstetrics and Gynaecology: International Practice and Research, September 1989. Ed. by C. J. G. Sunon. Pp. 429 + 686. Illustrated. £18,50. Northmead: WB Saunders. 1989.Management ofMinor Head Injuries. Ed. by I. J. Swann and D. W. Yates. Pp. x + 102. Illustrated: £14,95. Hampshire: Chapman & Hall Medical. 1989.ABC of Child Abuse. Ed. by Roy Meadow. Pp. 59. Illustrated. London: BMJ. 1989.The Facts of Life. Ed. by Marina Petropulos. Pp. 1 + 222. Illustrated. R19,95 exc!. GST. Cape Town: Tafelberg. 1990.Physical Examination of the Heart and Circulation. 2nd ed. Ed. by Joseph K. Perloff. Pp. viii + 292. Illustrated. £17,95. Northmead: WB Saunders. 1989.Growth Regulation of Thyroid Gland and Thyroid Tumours: Frontiers ofHormone Research. Vo!. 18. Ed. by P. E. Goretzki, and H. D. Roher. Pp. viii + 163. Illustrated. £68,80. Basel: S. Karger. 1989.Topical Diagnosis in Neurology: Anatomy, Physiology, Signs, Symptoms. 2nd revised ed. Ed. by P. Duus. Pp. x + 337. Illustrated. DM 370. Stungart: Georg Thieme Verlag. 1989