Mathematical models for ship path prediction in manoeuvring simulation systems

The problem of simulating the ship manoeuvring motion is studied mainly in connection with manoeuvring simulators. Several possible levels of solution to the problem with different degrees of complexity and accuracy are discussed. It is shown that the structure of the generic manoeuvring mathematical model leads naturally to two basic approaches based respectively on dynamic and purely kinematic prediction models. A simplified but fast dynamic manoeuvring model is proposed as well as two new advances in kinematic prediction methods: a prediction based on current values of velocities and accelerations and a method of anticipating the ship's trajectory in a course changing manoeuvre.     

Analysis of A Braced Excavation In Soft Soils Considering The Consolidation Effect

The studies of excavations in soft clayey soils are normally based on undrained total stress analyses. A better approach consists of taking into account the effects of consolidation during the excavation-bracing process and after the completion of the construction by means of coupled finite element analyses in effective stresses. In this paper, the geotechnical behaviour of a braced excavation in the soft soils of San Francisco (USA) is analysed, both during and after the construction period. Numerical analyses are performed with a finite element program, which incorporates the Biot consolidation theory (coupled formulation of the water flow and equilibrium equations) and soil constitutive relations simulated by the p-q-θ critical state model. Numerical results are compared with field results.     

Place-based social exclusion: redlining in the Netherlands

'Redlining' is a form of place-based exclusion. It is widely documented in the US, but not in Europe. This paper focuses on a comparative analysis of redlining practices in the two largest cities of the Netherlands: Amsterdam and Rotterdam. It shows that redlining was common practice in Rotterdam in 1999. In 2001, no signs of redlining were found in Rotterdam. However, 'yellowlining' (lower loan-to-value ratios) was still common in some parts of Rotterdam. In Amsterdam, no neighbourhoods were faced with redlining in either 1999 or 2001. However, in 1999 some neighbourhoods were yellowlined. This paper aims to get a better understanding of the nature and the institutional context of redlining in the Netherlands by explaining how the differences in redlining practices between Amsterdam and Rotterdam, and between 1999 and 2001, can be explained. The National Mortgage Guarantee as well as socio-historical, and housing and mortgage market differences and changes, are instrumental in explaining these differences in redlining practices.     

Unambiguous SAR signal reconstruction from nonuniform displaced phase center sampling

The displaced phase center (DPC) technique will enable a wide-swath synthetic aperture radar (SAR) with high azimuth resolution. In a classic DPC system, the pulse repetition frequency (PRF) has to be chosen such that the SAR carrier moves just one half of its antenna length between subsequent radar pulses. Any deviation from this PRF will result in a nonuniform sampling of the synthetic aperture. This letter derives an innovative reconstruction algorithm and shows that an unambiguous reconstruction of a SAR signal is possible for nonuniform sampling of the synthetic aperture. This algorithm will also have great potential for multistatic satellite constellations as well as the dual receive antenna mode in Radarsat 2 and TerraSAR-X.     

Models of Ground Deformation and Eruption Magnitude from a Deep Source at Popocatepetl Volcano,Central Mexico

Popocatepetl volcano in Central Mexico entered its latest stage of activity in late 1994. Due to the nature of its eruptive history and its location in a heavily populated area, it constitutes the highest risk in the cuntry. For this reason the volcano is currently under continuous surveillance; yet the interpretation of the information is carried out mostly on empirical basis and an integrating working model is lacking, at the present. In this paper, models of elastic deformation and mass erupted are developed to estimate the mass erupted according to the observed deformation patterns. We present results obtained from input based upon a gravimetric model of the volcano's internal structure and reasonable physical parameters of the volcanic system. These results are helpful in the planning of deformation and gravimetric observations aimed to forecast a major eruption.     

Determination of permeability in anisotropic rock-masses from integral samples

Summary Determination of Permeability in Anisotropic Rock-Masses From Integral SamplesA method is presented which makes it possible to characterize the permeability of a rock mass as an anisotropic magnitude — i. e. to determine its permeability tensor — from a characterization of its fracturing by means of integral samples.For the purpose, a theory is developed by means of which the permeability tensor can be calculated from the attitudes and openings of the fractures and — if infillings are present — also from their coefficient of permeability. All these magnitudes are determined in integral samples, it being assumed that the sampled fractures are continuous and plane, and have the same characteristics as the section of the fractures present in the samples. Possible deviations with respect to this assumption are taken into account by means of correcting factors derived from the results of pressure tests in situ. The permeability tensor of a rock mass at a point can be determined from a single integral sample, provided this is representative of the fracturing.Results of the application of the method are presented, which show it to look very promising.With 16 Figures     

Seismotectonics of Portugal and its adjacent area in the Atlantic

New elements on the seismicity of Portugal and new focal-mechanism solutions of earthquakes with epicentres situated off the coast of the Portuguese mainland and in the Azores region are presented. Historical seismicity data show that in the territory of the Portuguese mainland there are active faults that are responsible for earthquakes that have caused important damage and many casualties. However, most of the intraplate earthquakes with epicentres situated in the Portuguese mainland or near the shore are normally of small magnitude and this renders difficult their interpretation in the light of focal mechanisms. A solution for one earthquake, with magnitude 5 and epicentre at the Nazaré submarine canyon, is presented.Southwestwards of Cape St. Vincent there is an important seismic zone responsible for high-magnitude earthquakes such as that of 1 November 1755. This zone is situated in the region where the extension of the Messejana fault into the ocean joins with the Azores-Gibraltar fault.The seismicity of the area situated between the western coast of the Portuguese mainland and the Azores increases approximately along the 15°W meridian, from the latitude of the Azores-Gibraltar fault up to 44°N. Focal mechanisms of earthquakes with epicentres situated along this line show very similar solutions.The interpretation of the focal mechanism solutions of the earthquakes with epicentres situated in the studied area shows that the stress field trends approximately NW-SE. It is assumed that this stress field results from the interaction of the Eurasian and African plates; however, this direction is not maintained in the Azores region.     

Integrating in situ measurements of an index of connectivity to assess soil erosion processes in vineyards

ABSTRACT

In this research, we survey soil erosion processes using an index of connectivity and a non-invasive and long-term assessment in situ technique: the improved stock unearthing method (ISUM), for which the vineyard of Castilla La Mancha under tillage management was selected. Our results show, that in 10 years, the total average soil surface level decreased by – 1.6 cm and the total soil mobilization was up to 17.7 Mg ha^?1 year^?1. The surrounding lands of the survey plot showed meagre connectivity; however, smaller linear features with higher values were found as possible locations for potential rill generation. The survey plot is traversed by one of these linear features. In this inter-row survey, we found relatively low connectivity values. As a conclusion, we confirm that both methods can be useful to assess soil erosion processes in vineyards and detect areas that could increase the desertification as a consequence of non-sustainable soil erosion rates.     

Impacts of land-use and climate changes on surface runoff in a tropical forest watershed (Brazil)

ABSTRACT

Surface runoff generation capacity can be modified by land-use and climate changes. Annual runoff volumes have been evaluated in a small watershed of tropical forest (Brazil), using the Soil and Water Assessment Tool (SWAT) model. Firstly, the accuracy of SWAT in runoff predictions has been assessed by default input parameters and improved by automatic calibration, using 20-year observations. Then, the hydrological response under land uses (cropland, pasture and deforested soil) alternative to tropical forest and climate change scenarios has been simulated. SWAT application has showed that, if forest was replaced by crops or pasture, the watershed’s hydrological response would not significantly be affected. Conversely, a complete deforestation would slightly increase its runoff generation capacity. Under forecasted climate scenarios, the runoff generation capacity of the watershed will tend to decrease and will not be noticeably different among the representative concentration pathways. Pasture and bare soil will give the lowest and highest runoff coefficients, respectively.