Image Quality Control and Alignment of a Submillimeter Balloon-Borne Segmented Telescope

PRONAOS is a balloon-borne system dedicated to astronomical observations in the submillimeter range (180µm - 1050µm) based on the use of a 2m Cassegrain telescope. The primary mirror consists of six CFRP (Carbon Fiber Reinforced Plastic) panels, each being positioned by three actuators. The rotation angles of the panels have been measured in the visible range with the help of a CCD and digital centroiding techniques that were necessary because of the light scattering on the CFRP mirror. The translation movements (along the optical axis) of the panels have been measured with an interference technique in the submillimeter range. Both visible and submillimeter measurements were also necessary to determine the alignment of the telescope - focal instrument system with the star sensor. The whole alignment process leads to a precision of ±8 for the rotation angles and ±7µm for the translation of each panel, sufficient for a qualification of the system.     

Performance improvement studies of masonry houses using elastic post‐tensioning straps

Unreinforced masonry houses are composed of building blocks with weak inter‐binding action between them which commonly possess low tensile strength. The principal tensile stresses generated by out‐of‐plane bending and in‐plane shear forces cannot be tolerated well and leads to heavy structural damage and brittle collapse beyond linear capacity of the material. Remedies such as externally applied mesh reinforcement and post‐tensioning improves post and pre‐cracking performances; however, yielding of reinforcement material or shortening of walls due to cracking causes loss of integrity and post‐tensioning force. This paper discusses a research programme on earthquake strengthening of masonry houses using post‐tensioning by elastomeric straps and related shaking table tests on 1/10 scale single storey rural dwelling models. The aim of the study is to assess the use and effectiveness of post‐tensioning rubber straps at several different configurations especially for houses with heavy earth roofs supported on wooden logs. Full‐scale application can be conducted using scrap automobile tyres, which might be implemented as an economic and environment friendly alternative strengthening technique for poor residents of low‐cost dwellings. The performance and validity of the proposed strengthening techniques were tested on 1/10 scale models using a simplistic shaking table. The structural performance of the reinforced models with vertical post‐tensioning rubber straps was significantly improved as compared to the original specimen; the results were even better when vertical and horizontal straps were used. Obtained results show promise for seismic strengthening using rubber straps for post‐tensioning. Copyright © 2006 John Wiley & Sons, Ltd.     

A spatio-temporal Poisson hurdle point process to model wildfires

Wildfires have been studied in many ways, for instance as a spatial point pattern or through modeling the size of fires or the relative risk of big fires. Lately a large variety of complex statistical models can be fitted routinely to complex data sets, in particular wildfires, as a result of widely accessible high-level statistical software, such as R. The objective in this paper is to model the occurrence of big wildfires (greater than a given extension of hectares) using an adapted two-part econometric model, specifically a hurdle model. The methodology used in this paper is useful to determine those factors that help any fire to become a big wildfire. Our proposal and methodology can be routinely used to contribute to the management of big wildfires.     

A Life Cycle Comparison of Alternative Cheese Packages

A comparative life cycle assessment (LCA) between three different cheese packages (P1: completely polypropylene (PP), P2: tin and polyethylene (PE), and P3: carton and PE) has been carried out for the production, distribution and waste disposal (100% landfill) phase. A package for 1 kg of cheese was selected as the functional unit. SimaPro7 software (PRèConsultants, The Netherlands) was used for the LCA study. The EcoIndicator 99 method was selected for comparison of the packages. The comparisons show that the total environmental performance of the cheese package types in order from worst to best is P2, P1, and P3. This conclusion was supported by a sensitivity analysis, which was conducted by using different impact assessment methods.     

Earthquake shaking scenarios for the metropolitan area of Lisbon

In this study, we simulate and compare ground motion shaking in the city of Lisbon and surrounding counties (metropolitan area of Lisbon (MAL)), using two possible earthquake models: the onshore source area of Lower Tagus Valley, M5.7 and M4.7 and the offshore source area, Marques de Pombal Fault, M7.6, one of the possible source of the 1755 Lisbon earthquake. The stochastic and a new hybrid stochastic-deterministic approach (DSM) are used in order to evaluate the ground shaking and to characterize its spatial variability. Results are presented in terms of response acceleration spectra (PSA) and peak ground acceleration (PGA) with respect to bedrock and surface. Site effects are evaluated by means of equivalent stochastic non-linear one-dimensional ground responses analysis, performed for a set of stratified soil profile units properly designed to cope with the soil site conditions of MAL region. A sensitive study is carried out using different input parameters and different approaches in order to give the basic information to evaluate the range of uncertainty in seismic scenarios.     

Addressing some critical aspects of the BepiColombo MORE relativity experiment

The Mercury Orbiter Radio science Experiment (MORE) is one of the experiments on-board the ESA/JAXA BepiColombo mission to Mercury, to be launched in October 2018. Thanks to full on-board and on-ground instrumentation performing very precise tracking from the Earth, MORE will have the chance to determine with very high accuracy the Mercury-centric orbit of the spacecraft and the heliocentric orbit of Mercury. This will allow to undertake an accurate test of relativistic theories of gravitation (relativity experiment), which consists in improving the knowledge of some post-Newtonian and related parameters, whose value is predicted by General Relativity. This paper focuses on two critical aspects of the BepiColombo relativity experiment. First of all, we address the delicate issue of determining the orbits of Mercury and the Earth–Moon barycenter at the level of accuracy required by the purposes of the experiment and we discuss a strategy to cure the rank deficiencies that appear in the problem. Secondly, we introduce and discuss the role of the Solar Lense–Thirring effect in the Mercury orbit determination problem and in the relativistic parameters estimation.     

Extreme normalised residuals of daily temperatures in Catalonia (NE Spain): sampling strategies, return periods and clustering process

Extreme normalised residuals, defined as departures from the average values, of 65 daily maximum, T _max, and minimum, T _min, temperature series recorded in Catalonia (NE Spain) during 1950–2004 are analysed. Similarly to the sampling strategies applied to long dry spells, the partial duration series (PDS) offer some advantages in comparison with the annual extreme series. Instead of using a common percentile threshold for all temperature series, PDS are chosen according to the mean excess plot procedure. Series of extreme residuals are modelled, in terms of the L-moments formulation, by the generalised Pareto distribution. Extreme residuals of T _max and T _min are estimated for return periods ranging from 2 to 50 years and their spatial distribution is represented for selected return periods of 2, 5, 10, 25 and 50 years. Two daily extreme temperatures events, a hot episode (in August) and a cold episode (in February), are simulated taking into account the average T _max (T _min) for a day in August (February), their standard deviations and the extremes for a 50-year return period. Both simulations are compared with outstanding real episodes recorded on August 13th 2003 and February 11th 1956. Additionally, a spatial regionalisation of Catalonia in several clusters, in terms of the extreme residuals for return periods from 2 to 50 years, is done. A principal component analysis is applied to the extreme residual curves characterising every temperature series and, using as variables the principal components, the regionalisation is obtained by applying the average linkage clustering algorithm. Finally, each cluster is characterised by its average extreme residual curve for return periods ranging from 2 to 50 years at 1-year interval.