Evaluation of shoreline change using optical satellite images, case study of Progreso, Yucatán

A technique to extract the shoreline from optical satellite images has been developed, evaluated and applied to the case study site of Progreso, Yucatán, México. This site was chosen as it is frequently subject to hurricanes, shows shoreline erosion and has a paucity of coastal data. The area under investigation is an 8 km length of shoreline that faces north into the Gulf of México. A novel method to extract satellite-derived shorelines (SDS) was developed ensuring the maximum contrast between sea and land. The SDS was validated using quasisimultaneous in situ shoreline measurements from one day in two different years (2008 and 2010). The in situ shoreline measurements recorded the instantaneous shorewards extent of the wave run-up when walking along the beach. The validation of SDS revealed that the SDS locates consistently seawards of the in situ shoreline, explained by: a) the water depth that an optical satellite image requires to identify a pixel either as sea or land, and b) the shorewards extent of the wave run-up. At Progreso, the overall distance between SDS and in situ shoreline is 5.6 m on average and standard deviation of 1.37 m (in the horizontal) over 8 km of shoreline. For an accurate location of the mean SDS, estimation of the shorewards extent of the wave run-up, tidal level and inter-tidal beach slope were required. In situ measurements regarding the beach profile, shoreline location and water levels were taken into consideration to achieve this. The shoreline change observed over a 6.5 year period allowed the estimation of intraannual and inter-annual shoreline changes and progressive changes in the shoreline location. The intra-annual shoreline change revealed seasonality in the shoreline position. The shoreline position from late winter (March 20, 2004) was landwards (approx. 5 to 9 m) in relation to the earlier winter shoreline position (November 11, 2003). The assessed SDSs from the hurricane season (June to November) are at the landwards envelope limit during the year, between -30 to 15 m in relation to the estimated mean SDS. The largest landward movement (100 m) is related to Hurricane Ivan, detected 13 days after the hurricane passed by Yucatán. The inter-annual shoreline change highlighted that an approximate length of 6 km of shoreline is retreating at a rate between -2.4 and -1.2 m per year. Such estimates of shoreline change would not be possible using other available coastal information at this site. The results of this research show that optical satellite images can be used to study shoreline change over large spatial scales (> 5 km), as well as in short (< 1 yr) and long (> 5 yrs) temporal scales.CONACy

Advances in the Analysis of Properties Behaviour of Cement-Based Grouts with High Substitution of Cement with Blast Furnace Slags

This article presents a study of the main properties (consistency, workability, leaching, unsoundness, and mechanical properties) of cement grouts prepared with cement replacement by blast furnace slag (GGBS). Mixtures have been analyzed in the absence of additives and reached high replacement percentages. As shown in the different tests presented, the observed evolution of the resistance and workability of the mixtures makes them very interesting for its application. Different types of cement (CEM-I 42.5 and CEM-I 52.5 R) and different water/binder values (1 and 0.67) are used. The results present opportunities for the steel industry by the intensive valorization of slag waste. The reduction of the use of cement in construction is also one of the key aims of this line of research. Results show improvements in the mechanical response with good fresh state properties for substitution percentages up to 70%. It is verified with leaching analysis that these products have less impact on the environmen

Infinitesimal moduli for the Strominger system and Killing spinors in generalized geometry

We construct the space of infinitesimal variations for the Strominger system and an obstruction space to integrability, using elliptic operator theory. We initiate the study of the geometry of the moduli space, describing the infinitesimal structure of a natural foliation on this space. The associated leaves are related to generalized geometry and correspond to moduli spaces of solutions of suitable Killing spinor equations on a Courant algebroid. As an application, we propose a unifying framework for metrics with holonomy \SU(3) and solutions of the Strominger system.Comment: 48 pages. Section 5 and Appendix A from previous version have been suppressed and will appear elsewhere. Title slightly changed, references added, presentation improved. To appear in Math. Anna

Single-atom control of the optoelectronic response in sub-nanometric cavities

By means of ab-initio time dependent density functional theory calculations carried out on an prototypical hybrid plasmonic device (two metallic nanoparticles bridged by a one-atom junction), we demonstrate the strong interplay between photoinduced excitation of localized surface plasmons and electron transport through the single atom. Such an interplay is remarkably sensitive to the atomic orbitals of the junction. Therefore, we show the possibility of a twofold tuning (plasmonic response and photoinduced current across the juntion) just by changing a single atom in the device.Comment: 5 pages, 5 figure

Constructive Proofs or Constructive Statements?

A question raised at previous MAP meetings is the following. Is Sergeraert\u27s "Constructive Algebraic Topology" (CAT, in short) really constructive (in the strict logical sense of the word "constructive")? We have not an answer to that question, but we are interested in the following: could have a positive (or negative) answer to the previous question an influence in the problem of proving the correctness of CAT programs (as Kenzo)? Studying this problem, we have observed that, in fact, many CAT programs can be extracted from the statements (that is, from the specification of certain objects and constructions), without needing an extraction from proofs. This remark shows that the logic used in the proofs is uncoupled with respect to the correctness of programs. Thus, the first question posed could be quite irrelevant from the practical point of view. These rather speculative ideas will be illustrated by means of some elementary examples, where the Isabelle code extraction tool can be successfully applied

Alternative method for the metrological characterization of spur gears in the sub-millimeter range using optical equipment

The aim of this work is to develop a software that allows the inspection of spur gear manufactured in the sub-millimeter range. The measurements are made using a digital optical machine and using an analysis proprietary software implemented in Matlab®, which is able to handle images, captured using the digital optical machine. The software allows to evaluate the profile and pitch deviations as establish in the ISO/TR 10064-1:1992 standar

Climate Change and Copepod Size Distribution: Comparison of Two Coastal Long-Term Series in the Western Mediterranean Sea

This thesis was aimed at investigating long-term dynamics of zooplankton communities in relation to climate change. It represents a pioneer study in comparing Mediterranean time series with a standardised methodology, i.e., the ZooScan, a digital imaging system for counting and sizing mesozooplankton from preserved samples. This study has proven that copepod size spectra (i.e., histogram of organisms arranged by size classes) obtained with the ZooScan is a powerful synthetic index to monitor changes in the pelagic system. Copepod abundance and size spectra were analyzed in the zooplankton time series conducted at stn MC (Gulf of Naples, Tyrrhenian Sea) and Point B (Villefranche Bay, Ligurian Sea) for the years 1986-2005 and 1974-2003, respectively. In both time series, the proportion of large individuals in the copepod community increased over the years, with a shift in the early 1990s at stn MC and in 1987 at Point B. In both cases, the 1990s copepod reproduction might have decreased due to earlier and stronger stratification driven by rising temperature. At stn MC, the shift to dominance of small phytoplankton cells in the 1990s seemed to be the direct cause. At Point B, in addition to the detrimental effect of earlier stratification in the 1990s, the 1980s seemed to be very productive due to strong winter convection driven by cool salty winters. High salinity was related to low winter atmospheric pressure linked to the North Atlantic Oscillation (+ winter NAO). In both locations, the frequency of occurrence of typical offshore species increased over the years, suggesting changes in coastal-offshore interactions. Mechanisms controlling the copepod communities in both sites seem to be different. Stn MC has a more coastal character than Point B and thus the former is more affected by local conditions as terrestrial nutrient inputs. At Point B, stratification-destratification dynamics seem to control production