Fast full-wave scattering at extremely large and complex multiscale objects

In recent years, the computational electromagnetics community has witnessed a rapid increase in the electrical size of scattering problems that can be solved. This increase can be mainly attributed to the use of boundary integral equations and the development of the multilevel fast multipole algorithm (MLFMA) and its parallelized analogues. However, many challenges remain, especially when it comes to broadband behavior and large and complex multiscale geometries. The geometrical problem, on the one hand, is adequately solved by means of a very accurate calculation of the moment integrals. This is accomplished by using the singularity extraction method not only for the selfpatch but also for the neighbor contribution. On the other hand, the problem with the LF-breakdown of the MLFMA is solved by switching to the so-called normalized plane wave method (NPWM) for the lowest levels. This method is error-controllable at LF but still uses plane waves and thus leads to diagonal translations, unlike multipole based methods. Additionally, these techniques were incorporated in the parallel framework open FMM, such that the large number of unknowns necessary for the discretization of the geometry can be handled

Ferroelastic phase transitions and anelastic dissipation in the LaAlO₃-PrAlO₃ solid solution series

Resonant ultrasound spectroscopy has been used on single-crystal samples to observe pseudoproper ferroelastic softening across the (La,Pr)AlO₃ solid solution. It is suggested that softening is due to the presence of an intrinsic zone-center instability in addition to the small Jahn-Teller stabilization expected for Pr³⁺. Softening increases as smaller Pr³⁺ ions are substituted for larger La³⁺ which is attributed to a simple size effect as well as the possibility of bilinear coupling of the intrinsic instability with the weak Jahn-Teller effect. Superattenuation is observed above 600 K for all samples, which is consistent with twin wall related dissipation behavior seen in other perovskites with octahedral tilting. Superattenuation is also observed in the lowtemperature monoclinic phase, implying a high mobility also for the monoclinic twin walls

Synchrotron Topographic Studies of Domain Structure in Czochralski Grown PrxLa1−xAlO3\mathrm{Pr_{x}La_{1-x}AlO_{3}} and PrxLa1−x−yMgyAlO3\mathrm{Pr_{x}La_{1-x-y}Mg_{y}AlO_{3}} Crystals

A domain structure and crystallographic defects in Czochralski grown single crystals of $Pr_xLa_{1-x}AlO_3$ and $Pr_xLa_{1-x-y}Mg_yAlO_3$ were characterised with a number of methods including conventional and synchrotron X-ray diffraction topography, and polariscopic micrography. The observed twin domain systems were located perpendicularly to 〈100〉$\text{}_\text{pcub}$ and 〈110〉$\text{}_\text{pcub} (pseudocubic) directions. It has been confirmed that the domains are of the same orientation and a twin character as those described in literature for$LaAlO_3$and$LaGaO_3$crystals. The use of section transmission topography enabled to indicate that the domains are perpendicular to the$(100)_\text{pcub}$ surface of the samples. The misorientation of lattice in the domains was evaluated from the white beam topographs and a tendency of its increase with increasing concentration of praseodymium was revealed