Toward Coarse-Grained Elasticity of Single-Layer Covalent Organic Frameworks

Two-dimensional covalent organic frameworks (2D COFs) are an interesting class of 2D materials since their reticular synthesis allows the tailored design of structures and functionalities. For many of their applications, the mechanical stability and performance is an important aspect. Here, we use a computational approach involving a density-functional based tight-binding method to calculate the in-plane elastic properties of 45 COFs with a honeycomb lattice. Based on those calculations, we develop two coarse-grained descriptions: one based on a spring network and the second using a network of elastic beams. The models allow us to connect the COF force constants to the molecular force constants of the linker molecules and thus enable an efficient description of elastic deformations. To illustrate this aspect, we calculate the deformation energy of different COFs containing the equivalent of a Stone-Wales defect and find very good agreement with the coarse-grained description

“Luck’s always to blame”: silent wounds of a penetrating gunshot trauma sustained 20 years ago

Gunshot tracheal injuries represent life-threatening events and usually necessitate emergent surgical intervention. We report a case of an exceptional finding of a patient with retained ballistic fragments in the soft tissues of the thorax, proximal to the right subclavian artery and the trachea, carrying silently his wounds for two decades without any medical or surgical intervention. The bullet pellet on the upper part of the trachea seen accidentally in the chest computed tomography, was also found during bronchoscopy. In short “luck’s always to blame”

Seismic wave amplification: Basin geometry vs soil layering.

International audienceThe main purpose of the paper is to analyze seismic site effects in alluvial basins and to discuss the influence of the knowledge of the local geology on site amplification simulations. Wave amplification is due to a combined effect of impedance ratio between soil layers and surface wave propagation due to the limited extent of the basin. In this paper, we investigate the influence of the complexity of the soil layering (simplified or detailed layering) on site effects in both time and frequency domain. The analysis is performed by the Boundary Element Method. The European test site of Volvi (Greece) is considered and 2D amplification in the basin is investigated for various soil models. Seismic signals are computed in time domain for synthetic Ricker signals as well as actual measurements. They are analyzed in terms of amplification level as well as time duration lengthening (basin effects) for both SH and SV waves. These results show that the geometry of the basin has a very strong influence on seismic wave amplification in terms of both amplification level and time duration lengthening. The combined influence of geometry/layering of alluvial basins seems to be very important for the analysis of 2D (3D) site effects but a simplified analysis could sometimes be sufficient. In the case of Volvi European test site, this influence leads to (measured and computed) 2D amplification ratios far above 1D estimations from horizontal layering descriptions

Understanding single-station ground motion variability and uncertainty (sigma) – Lessons learnt from EUROSEISTEST

Accelerometric data from the well-studied valley EUROSEISTEST are used to investigate ground motion uncertainty and variability. We define a simple local ground motion prediction equation (GMPE) and investigate changes in standard deviation (σ) and its components, the between-event variability (τ) and within-event variability (φ). Improving seismological metadata significantly reduces τ (30-50%), which in turn reduces the total σ. Improving site information reduces the systematic site-to-site variability, φS2S (20-30%), in turn reducing φ, and ultimately, σ. Our values of standard deviations are lower than global values from literature, and closer to path-specific than site-specific values. However, our data have insufficient azimuthal coverage for single-path analysis. Certain stations have higher ground-motion variability, possibly due to topography, basin edge or downgoing wave effects. Sensitivity checks show that 3 recordings per event is a sufficient data selection criterion, however, one of the dataset’s advantages is the large number of recordings per station (9-90) that yields good site term estimates. We examine uncertainty components binning our data with magnitude from 0.01 to 2 s; at smaller magnitudes, τ decreases and φSS increases, possibly due to κ and source-site trade-offs Finally, we investigate the alternative approach of computing φSS using existing GMPEs instead of creating an ad hoc local GMPE. This is important where data are insufficient to create one, or when site-specific PSHA is performed. We show that global GMPEs may still capture φSS, provided that: 1. the magnitude scaling errors are accommodated by the event terms; 2. there are no distance scaling errors (use of a regionally applicable model). Site terms (φS2S) computed by different global GMPEs (using different site-proxies) vary significantly, especially for hard-rock sites. This indicates that GMPEs may be poorly constrained where they are sometimes most needed, i.e. for hard rock

2D characterization of near-surface V P/V S: surface-wave dispersion inversion versus refraction tomography

International audienceThe joint study of pressure (P-) and shear (S-) wave velocities (Vp and Vs ), as well as their ratio (Vp /Vs), has been used for many years at large scales but remains marginal in near-surface applications. For these applications, and are generally retrieved with seismic refraction tomography combining P and SH (shear-horizontal) waves, thus requiring two separate acquisitions. Surface-wave prospecting methods are proposed here as an alternative to SH-wave tomography in order to retrieve pseudo-2D Vs sections from typical P-wave shot gathers and assess the applicability of combined P-wave refraction tomography and surface-wave dispersion analysis to estimate Vp/Vs ratio. We carried out a simultaneous P- and surface-wave survey on a well-characterized granite-micaschists contact at Ploemeur hydrological observatory (France), supplemented with an SH-wave acquisition along the same line in order to compare Vs results obtained from SH-wave refraction tomography and surface-wave profiling. Travel-time tomography was performed with P- and SH- wave first arrivals observed along the line to retrieve Vtomo p and Vtomo s models. Windowing and stacking techniques were then used to extract evenly spaced dispersion data from P-wave shot gathers along the line. Successive 1D Monte Carlo inversions of these dispersion data were performed using fixed Vp values extracted from Vtomo p the model and no lateral constraints between two adjacent 1D inversions. The resulting 1D Vsw s models were then assembled to create a pseudo-2D Vsw s section, which appears to be correctly matching the general features observed on the section. If the pseudo-section is characterized by strong velocity incertainties in the deepest layers, it provides a more detailed description of the lateral variations in the shallow layers. Theoretical dispersion curves were also computed along the line with both and models. While the dispersion curves computed from models provide results consistent with the coherent maxima observed on dispersion images, dispersion curves computed from models are generally not fitting the observed propagation modes at low frequency. Surface-wave analysis could therefore improve models both in terms of reliability and ability to describe lateral variations. Finally, we were able to compute / sections from both and models. The two sections present similar features, but the section obtained from shows a higher lateral resolution and is consistent with the features observed on electrical resistivity tomography, thus validating our approach for retrieving Vp/Vs ratio from combined P-wave tomography and surface-wave profiling

Methodological framework for locational evaluation of accessibility of public services. Application in the ares of the municipality of Heraklion Crete

125 σ.Θέμα της παρούσας διπλωματικής εργασίας είναι η ανάλυση της χωροθέτησης της προσβασιμότητας των δημόσιων υπηρεσιών με συνδυασμό με πληθυσμιακά χαρακτηριστικά καθώς και με οικονομικούς δείκτες (τιμή ζώνης), με εφαρμογή στην ευρύτερη περιοχή του δήμου Ηρακλείου Κρήτης. Η διαδικασία πραγματοποιήθηκε με χρήση λογισμικού ArcGIS 10. Πρώτο βήμα στην εργασία αποτέλεσε η συλλογή των απαραίτητων στοιχείων για την εξαγωγή της πληθυσμιακής κατάστασης, του δείκτη προσβασιμότητας και της τιμής ζώνης στο σύνολο των οικοδομικών τετραγώνων για τον δήμο. Στη συνέχεια, με την βοήθεια στατιστικών μεθόδων, προκύπτει το πληθυσμικό προφιλ του δήμου για κάθε εξεταζόμενο χαρακτηριστικό ξεχωριστά (ηλικία, επάγγελμα, εισόδημα) καθώς και ο συνδιασμός τους. Δεύτερο βήμα στην εργασία αποτέλεσε η μελέτη της προσβασιμότητας των οικοδομικών τετραγώνων προς τις δημόσιες υπηρεσίες η οποία πραγματοποιήθικε με δύο διαφορετικά εργαλεία επεξεργασίας. Το πρώτο μελετά το πλήθος των υπηρεσιών σε ακτίνα γύρω απο κάθε οικοδόμικό τετράγνωνο, και το δεύτερο μελετά την ελάχιστη απόσταση κάθε κατηγορίας υπηρεσιών από το κάθε οικοδομικό τετράγωνο. Το τρίτο και τελευταίο στάδιο αποτελείται απο τις συνδυαστικές μελέτες του προφίλ και της προσβασιμότητας ,και της τιμής ζώνης με την προσβασιμότητα. Η εφαρμογή του παραπάνω μεθοδολογικού πλαισίου στο Δήμο Ηρακλείου Κρήτης (πρόγραμμα Καποδίστριας) οδήγησε στην ερμηνεία των παραγόμενων αποτελεσμάτων σχετικά με την προσβασιμότητα που παρουσιάζουν οι διάφορες περιοχές του δήμου, τα οποία μπορούν να χρησιμοποιηθούν κατα τον μελοντικό πολεοδομικό σχεδιασμό του δήμου.This thesis is concerned with layout evaluation of public services in correlation with the varied features of the inhabitants and with economic indicators (value of building block), with implementation to the municipality of Heraklion, Crete. The procedure has been accomplished with the use of the software ArcGIS 10. The first part of our thesis includes the collection of the necessary data for the construction of the concept of accessibility, the formation of the indicators of accessibility and the value of building blocks to whore squares of buildings for the municipality. In the second part, by the application of statistic data we deduce the profil of building blocks for each studied feature separately (age, occupation,income) as their combination. Secondly, we evaluate the accdessibility of building squares to public services with two different ways. The first one studies the number of public services around from each building block and the second one studies the minimum distance from each building block. The last but not leaste stage of this framework includes the combination of the above results the profil with the accessibility, and the accessibility with the location value of each building block . By applying this model to the municipality of Heraklion Crete (Kapodistria's reform) came to conclusion as regards the accessibility of different areas to this minicipality which could be employed in the future urban planning of this city.Γεώργιος Δ. Ραπτάκη