Hydro-mechanical coupled dual domain material point method stabilized with a null-space filter

The Material Point Method (MPM) is a continuum-based numerical method especially suitable for solving large deformation problems. In this paper, we investigate the null-space errors present in MPM solutions. The paper establishes a null-space stability condition which is used to examine the null-space errors in different versions of the MPM. This analysis shows that a B-splines MPM satisfies the null-space stability condition and therefore reduces greatly the errors associated with the null-space. In contrast, the MPM, the Generalized Interpolation Material Point Method (GIMP) and the Dual Domain Material Point Method (DDMP) show non-trivial null-spaces in the mapping. To remove the null-space errors, this paper utilizes QR factorization method, which is similar to the Single Value Decomposition (SVD) method, but requires fewer computations. This paper simulates several problems with hydro-mechanical coupled Dual Domain Material Point Method (DDMP) formulation both with and without null-space error reduction. The simulations indicate that the null-space filter can improve significantly the accuracy of the pore water pressure for both gravity loading and consolidation in large strain simulation

Preliminary results of a silver carp breeding program in Vietnam

The article describes the silver carp (Hypophthalmichthys harmandi and Hypophthalmichthys molitrix) breeding program in Vietnam

Preliminary results of a silver carp breeding program in Vietnam

Selective breeding, Aquaculture techniques, Vietnam, Hypophthalmichthys harmandi, Hypophthalmichthys molitrix

Power allocation policy and performance analysis of secure and reliable communication in cognitive radio networks

This paper investigates the problem of secure and reliable communications for cognitive radio networks. More specifically, we consider a single input multiple output cognitive model where the secondary user (SU) faces an eavesdropping attack while being subject to the normal interference constraint imposed by the primary user (PU). Thus, the SU must have a suitable power allocation policy which does not only satisfy the constraints of the PU but also the security constraints such that it obtains a reasonable performance for the SU, without exposing information to the eavesdropper. We derive four power allocation policies for different scenarios corresponding to whether or not the channel state information of the PU and the eavesdropper are available at the SU. Further, we introduce the concept secure and reliable communication probability (SRCP) as a performance metric to evaluate the considered system, as well as the efficiency of the four power allocation policies. Finally, we present numerical examples to illustrate the power allocation polices, and the impact of these policies on the SRCP of the SU. SafeCOP - Safe Cooperating Cyber-Physical Systems using Wireless Communicatio

Modelling of the quickness test of sensitive clays using the generalized interpolation material point method

The presence of the sensitive clays in Scandinavia and Canada creates quick clay landslide hazards. The ability to predict the likelihood of such landslides occurrence, as well as their outreach would reduce the damage to the infrastructures and loss of life. Recently, a simple experimental technique named a quickness test (Thakur V, Degago S, Geotech Lett 2:87-95, 2012) has been employed to investigate the susceptibility of the clay to create large retrogression landslides. In this paper, we applied Generalized Interpolation Material Point Method (a numerical method suitable for large displacement dynamic problems) to replicate the quickness test experiment. The primary goal of the presented simulations is to further validate the modelling technique and the constitutive model used. In particular, the computations suggest the importance of the strain rates for the prediction of the run-out distance of the remoulded sensitive clays

Material point method: Overview and challenges ahead

The paper gives an overview of Material Point Method and shows its evolution over the last 25 years. The Material Point Method developments followed a logical order. The article aims at identifying this order and show not only the current state of the art, but explain the drivers behind the developments and identify what is currently still missing. The paper explores modern implementations of both explicit and implicit Material Point Method. It concentrates mainly on uses of the method in engineering, but also gives a short overview of Material Point Method application in computer graphics and animation. Furthermore, the article gives overview of errors in the material point method algorithms, as well as identify gaps in knowledge, filling which would hopefully lead to a much more efficient and accurate Material Point Method. The paper also briefly discusses algorithms related to contact and boundaries, coupling the Material Point Method with other numerical methods and modeling of fractures. It also gives an overview of modeling of multi-phase continua with Material Point Method. The paper closes with numerical examples, aiming at showing the capabilities of Material Point Method in advanced simulations. Those include landslide modeling, multiphysics simulation of shaped charge explosion and simulations of granular material flow out of a silo undergoing changes from continuous to discontinuous and back to continuous behavior. The paper uniquely illustrates many of the developments not only with figures but also with videos, giving the whole extend of simulation instead of just a timestamped image