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Deformation Model (deformation + model)
Selected AbstractsRange Scan Registration Using Reduced Deformable ModelsCOMPUTER GRAPHICS FORUM, Issue 2 2009W. Chang Abstract We present an unsupervised method for registering range scans of deforming, articulated shapes. The key idea is to model the motion of the underlying object using a reduced deformable model. We use a linear skinning model for its simplicity and represent the weight functions on a regular grid localized to the surface geometry. This decouples the deformation model from the surface representation and allows us to deal with the severe occlusion and missing data that is inherent in range scan data. We formulate the registration problem using an objective function that enforces close alignment of the 3D data and includes an intuitive notion of joints. This leads to an optimization problem that we solve using an efficient EM-type algorithm. With our algorithm we obtain smooth deformations that accurately register pairs of range scans with significant motion and occlusion. The main advantages of our approach are that it does not require user specified markers, a template, nor manual segmentation of the surface geometry into rigid parts. [source] Mechanical deformation model of the western United States instantaneous strain-rate fieldGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2006Fred F. Pollitz SUMMARY We present a relationship between the long-term fault slip rates and instantaneous velocities as measured by Global Positioning System (GPS) or other geodetic measurements over a short time span. The main elements are the secularly increasing forces imposed by the bounding Pacific and Juan de Fuca (JdF) plates on the North American plate, viscoelastic relaxation following selected large earthquakes occurring on faults that are locked during their respective interseismic periods, and steady slip along creeping portions of faults in the context of a thin-plate system. In detail, the physical model allows separate treatments of faults with known geometry and slip history, faults with incomplete characterization (i.e. fault geometry but not necessarily slip history is available), creeping faults, and dislocation sources distributed between the faults. We model the western United States strain-rate field, derived from 746 GPS velocity vectors, in order to test the importance of the relaxation from historic events and characterize the tectonic forces imposed by the bounding Pacific and JdF plates. Relaxation following major earthquakes (M, 8.0) strongly shapes the present strain-rate field over most of the plate boundary zone. Equally important are lateral shear transmitted across the Pacific,North America plate boundary along ,1000 km of the continental shelf, downdip forces distributed along the Cascadia subduction interface, and distributed slip in the lower lithosphere. Post-earthquake relaxation and tectonic forcing, combined with distributed deep slip, constructively interfere near the western margin of the plate boundary zone, producing locally large strain accumulation along the San Andreas fault (SAF) system. However, they destructively interfere further into the plate interior, resulting in smaller and more variable strain accumulation patterns in the eastern part of the plate boundary zone. Much of the right-lateral strain accumulation along the SAF system is systematically underpredicted by models which account only for relaxation from known large earthquakes. This strongly suggests that in addition to viscoelastic-cycle effects, steady deep slip in the lower lithosphere is needed to explain the observed strain-rate field. [source] Viscoelastic displacement and gravity changes due to point magmatic intrusions in a gravitational layered solid earthGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2001José Fernández Summary We present a method for the computation of time-dependent geodetic and geophysical signatures (deformation, potential and gravity changes) due to magmatic intrusions in a layered viscoelastic,gravitational medium. This work is an extension of a deformation model previously developed to compute effects due to volcanic loading in an elastic gravitational layered media. The model assumes a planar earth geometry, useful for near field problems, and consists of welded elastic and viscoelastic layers overlying a viscoelastic half-space. Every layer can either be considered elastic or viscoelastic. The intrusion (treated as a point source) can be located at any depth, in any of the layers or in the half-space. Several examples of theoretical computations for different media are also presented. We have found that, in line with previous results obtained by other authors, introducing viscoelastic properties in all or part of the medium can extend the effects (displacements, gravity changes, etc.) considerably and therefore lower pressure increases are required to model given observed effects. The viscoelastic effects seem to depend mainly on the rheological properties of the layer (zone) where the intrusion is located, rather than on the rheology of the whole medium. We apply our model to the 1982,1984 uplift episode at Campi Flegrei, modelling simultaneously the observed vertical displacement and gravity changes. The results clearly show that for a correct interpretation of observed effects it is necessary to include the gravitational field in the anelastic theoretical models. This factor can change the value and pattern of time-dependent deformation as well as the gravity changes, explaining cases of displacement without noticeable gravity changes or vice versa, cases with uplift and incremental gravity values, and other cases. The combination of displacement and gravity changes is found to be especially effective in constraining the possible characteristics of the magmatic intrusion as well as the rheology of the medium surrounding it. [source] Solute transport through a deforming porous mediumINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 7 2002Glen P. Peters Abstract Solute transport through a porous medium is typically modelled assuming the porous medium is rigid. However, many applications exist where the porous medium is deforming, including, municipal landfill liners, mine tailings dams, and land subsidence. In this paper, mass balance laws are used to derive the flow and transport equations for a deforming porous medium. The equations are derived in both spatial and material co-ordinate systems. Solute transport through an engineered landfill liner is used as an illustrative example to show the differences between the theory for a rigid porous medium, and small and large deformation analysis of a deforming porous medium. It is found that the large deformation model produces shorter solute breakthrough times, followed by the small deformation model, and then the rigid porous medium model. It is also found that it is important to include spatial and temporal void ratio variations in the large deformation analysis. It is shown that a non-linear large deformation model may greatly reduce the solute breakthrough time, compared to a standard transport analysis typically employed by environmental engineers. Copyright © 2002 John Wiley & Sons, Ltd. [source] A numerical simulation on diffuser-nozzle based piezoelectric micropumps with two different numerical modelsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 4 2007Jin Jeong Abstract This study has been conducted to compare two different numerical models for the evaluation of the performance characteristics of a diffuser-nozzle based piezoelectric micropump. Here, the transient displacements of the membrane and the flow characteristics in the piezoelectric micropump have been closely investigated with the FSI model and the prescribed deformation model for two different frequencies. It has been found that the behaviour of the membrane computed with the FSI model is not in accordance with that with the prescribed deformation model, and that the net flow rate with the FSI model is larger than that with the prescribed deformation model. Therefore, the choice of numerical model is very important in conducting numerical analysis for piezoelectric micropumps. The results of this study can be utilized as basic data for the design and analysis of piezoelectric micropumps. Copyright © 2006 John Wiley & Sons, Ltd. [source] A preliminary study of crustal structure in Taiwan region using receiver function analysisGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2004Kwang-Hee Kim SUMMARY Selected teleseismic data observed at temporary and permanent broad-band stations have been analysed using the receiver function method in order to investigate the very complex crustal structure in Taiwan region. Very significant azimuthal variations of radial and transverse receiver function responses from broad-band stations could be attributed to, among other things, the sampling of incoming seismic waves across the nearby subduction zone, a subsurface dipping interface, or a localized anisotropic region. A mid-crust discontinuity, interpreted as the Conrad discontinuity, can be identified at 18,20 km depth beneath TATO and TPUB stations in the Western Foothills, but is absent beneath the two nearby stations SSLB and TDCB in the Central Mountain Range. The separation of upper and lower crust beneath the Western Foothills and the steady increase in crustal velocity as a function of depth across the entire thicker crust beneath the Central Mountain Range suggest that the tectonic evolution of the crust may be significantly different for these two adjacent regions. Although a ,thin-skinned' model may be associated with the tectonic evolution of the upper crust of the Western Foothills and Western Coastal Plain, a ,thick-skinned' or ,lithospheric deformation' model can probably be applied to explain the crustal evolution of the Central Mountain Range. A trend of crustal thinning from east (50,52 km) to west (28,32 km) is in very good agreement with the results from two east,west-trending deep seismic profiles obtained using airgun sources. The thinner crust (20,30 km) beneath TWB1 station in northeastern Taiwan can be associated with the high-heat-flow backarc opening at the western terminus of the Okinawa trough behind the subduction of the Philippine Sea plate. The relatively simple crustal structure beneath KMNB station, offshore southeastern China, depicts typical continental crust, with the Moho depth at 28,32 km. An apparent offset of the thickest Moho beneath NACB station from the topographic high in the central Central Mountain Range suggests that the Taiwan orogeny has probably not reached its isostatic status. [source] | ||||||||||