In this study 2d two phase microstructures closely resembling the experimentally captured micrographs of the interpenetrating phase composites are generated using a Gaussian correlation function based method. The scale dependent bounds on the effective thermal conductivity of such microstructures are then studied using Hill-Mandel boundary conditions. A scaling function is formulated to describe the transition from statistical volume element (SVE) to representative volume element (RVE), as a function of the mesoscale δ, the correlation length of the Gaussian correlation function λ, the volume fraction v, and the contrast k between the phases. The scaling function is determined through fitting the data from extensive simulations conducted over the parameter space. The scaling function shows that SVE approaches RVE as (δ/λ)−1.16. A material scaling diagram allows estimation of the RVE size, to within a chosen accuracy, of a given microstructure characterized by the correlation length of the Gaussian correla...

Modern numerical algorithms for computational electromagnetics lead to many large sparse systems of linear equations. Their solution takes up to 90% of the total computational time in the geophysical inversion process. This paper provides evaluation and comparison of several state-of-the-art direct solvers in a massively parallel environment. We determine the largest complex systems that can be solved today with these methods and evaluate their performance and scalability on one of the world’s most powerful supercomputers. Small sensitivity of direct methods to the number of sources, modeling frequency and conductivity distribution in the subsurface is confirmed. The results show the potentials and limitations of different parallel implementations on a petascale high-performance computing system.

Micro- and nanoscale tubular structures can be formed by strain-induced self-rolled-up nanomembranes. Precision engineering of the shape and dimension determines the performance of devices based on this platform for electronic, optical, and biological applications. A transient quasi-static finite element method (FEM) with moving boundary conditions is proposed as a general approach to design diverse types of three-dimensional (3D) rolled-up geometries. This method captures the dynamic release process of membranes through etching driven by mismatch strain and accurately predicts the final dimensions of rolled-up structures. Guided by the FEM modeling, experimental demonstration using silicon nitride membranes was achieved with unprecedented precision including controlling fractional turns of a rolled-up membrane, anisotropic rolling to form helical structures, and local stress control for 3D hierarchical architectures.

Alya is the BSC in-house HPC-based multi-physics simulation code. It is designed from scratch to run efficiently in parallel supercomputers, solving coupled problems. The target domain is engineering, with all its particular features: complex geome- tries and unstructured meshes, coupled multi-physics with exotic coupling schemes and Physical models, ill-posed problems, flexibility needs for rapidly including new models, etc. Since its conception in 2004, Alya has shown scaling behaviour in an increasing number of cores. In this paper, we present its performance up to 100.000 cores in Blue Waters, the NCSA supercomputer. The selected tests are representative of the engineering world, all the problematic features included: incompressible flow in a hu- man respiratory system, low Mach combustion problem in a kiln furnace and coupled electro-mechanical problem in a heart. We show scalability plots for all cases, discussing all the aspects of such kind of simulations, including solvers convergence.