Stability fem analysis of rock masses modeling pattern of joints

In the south of the city of Morelia, Mexico, there is a geological normal fault denominated "La Paloma". It has a height of 180 m and has limited the growth of the city. To improve the connectivity of the city, an urban road is building and it includes the digging of a tunnel that goes through this fault. Due to the presence of an ancient landslide in the exit tunnel, it is imperative to verify the stability of a slope in this zone. The geological structures founded “in situ” make complex the stability analyses, but the used of more realistic representation helps to understand the mechanism of failure. The data collected in geotechnical explorations helped to construct several models for slope stability analysis. Rocks and soils were identified in the interest area. In this way, an elastoplastic Finite Element Analysis (FEA) was carried out to verify the slope stability, considering a strength reduction by a safety factor. Stability was revised in static and seismic conditions. The rock structure is represented by using the Modified Hoek and Brown constitutive model and patterns of the joints with a Mohr-Coulomb constitutive model. The fragments of rock were emulated with joint patterns according to the geologic structure. The slope stability results show a stable slope considering static and pseudo-static FEA analysis. The failure mechanism could be appreciated with the slope stability analysis realized

THE SPANISH PENSION SYSTEM: ISSUES OF INTRODUCING NOTIONAL DEFINED CONTRIBUTION ACCOUNTS

There are two aims to this paper: firstly, to provide an objective technical assessment of the current situation of the contributory pension system in Spain and its prospects for the future, and secondly, to look at the issues surrounding the introduction of a system of notional defined contribution accounts. To this end we explain the basic elements upon which the current system is based and show its main indicators, then set out some of its fundamental problems. Following this we look at the most relevant research work, where forecasts can be found that will give us a clear idea of the system's financial sustainability. Finally we put forward an argument as to why a notional accounts system could be a valid alternative for reforming the current system, and suggest which formula or group of formulas would best fit the profile of contributor-beneficiary risk and what the transition process would beRetirement, Pay-as-you-go, Internal Rate of Return (IRR), Financial sustainability.

The puzzle of the CNO isotope ratios in AGB carbon stars

Previous determinations of the oxygen isotopic ratios in AGB carbon stars were at odds with the existing theoretical predictions. We aim to redetermine the oxygen ratios in these stars using new spectral analysis tools and further develop discussions on the carbon and nitrogen isotopic ratios in order to elucidate this problem. Oxygen isotopic ratios were derived from spectra in the K-band in a sample of galactic AGB carbon stars of different spectral types and near solar metallicity. Synthetic spectra calculated in LTE with spherical carbon-rich atmosphere models and updated molecular line lists were used. The CNO isotope ratios derived in a homogeneous way, were compared with theoretical predictions for low-mass (1.5-3 M_o) AGB stars computed with the FUNS code assuming extra mixing both during the RGB and AGB phases. For most of the stars the 16O/17O/18O ratios derived are in good agreement with theoretical predictions confirming that, for AGB stars, are established using the values reached after the FDU according to the initial stellar mass. This fact, as far as the oxygen isotopic ratios are concerned, leaves little space for the operation of any extra mixing mechanism during the AGB phase. Nevertheless, for a few stars with large 16O/17O/18O, the operation of such a mechanism might be required, although their observed 12C/13C and 14N/15N ratios would be difficult to reconcile within this scenario. Furthermore, J-type stars tend to have lower 16O/17O ratios than the normal carbon stars, as already indicated in previous studies. Excluding these peculiar stars, AGB carbon stars occupy the same region as pre-solar type I oxide grains in a 17O/16O vs. 18O/16O diagram, showing little spread. This reinforces the idea that these grains were probably formed in low-mass stars during the previous O-rich phases.Comment: Accepted fo publication in A&

Second-order neural core for bioinspired focal-plane dynamic image processing in CMOS

Based on studies of the mammalian retina, a bioinspired model for mixed-signal array processing has been implemented on silicon. This model mimics the way in which images are processed at the front-end of natural visual pathways, by means of programmable complex spatio-temporal dynamic. When embedded into a focal-plane processing chip, such a model allows for online parallel filtering of the captured image; the outcome of such processing can be used to develop control feedback actions to adapt the response of photoreceptors to local image features. Beyond simple resistive grid filtering, it is possible to program other spatio-temporal processing operators into the model core, such as nonlinear and anisotropic diffusion, among others. This paper presents analog and mixed-signal very large-scale integration building blocks to implement this model, and illustrates their operation through experimental results taken from a prototype chip fabricated in a 0.5-μm CMOS technology.European Union IST 2001 38097Ministerio de Ciencia y Tecnología TIC 2003 09817 C02 01Office of Naval Research (USA) N00014021088