Suzaku and XMM-Newton Observations of the North Polar Spur: Charge Exchange or ISM Absorption?

By revisiting the Suzaku and XMM-Newton data of the North Polar Spur, we discovered that the spectra are inconsistent with the traditional model consisting of pure thermal emission and neutral absorption. The most prominent discrepancies are the enhanced O VII and Ne IX forbidden-to-resonance ratios, and a high O VIII Ly$\beta$ line relative to other Lyman series. A collisionally ionized absorption model can naturally explain both features, while a charge exchange component can only account for the former. By including the additional ionized absorption, the plasma in the North Polar Spur can be described by a single-phase CIE component with temperature of 0.25 keV, and nitrogen, oxygen, neon, magnesium, and iron abundances of $0.4-0.8$ solar. The abundance pattern of the North Polar Spur is well in line with those of the Galactic halo stars. The high nitrogen-to-oxygen ratio reported in previous studies can be migrated to the large transmission of the O VIII Ly$\alpha$ line. The ionized absorber is characterized by a balance temperature of $0.17-0.20$ keV and a column density of $3-5 \times 10^{19}$ cm$^{-2}$. Based on the derived abundances and absorption, we speculate that the North Polar Spur is a structure in the Galactic halo, so that the emission is mostly absorbed by Galactic ISM in the line of sight.Comment: Accepted for publication in Astronomy and Astrophysic

GPU-Accelerated Boundary Element Method for Stress Analysis of Underground Excavations

Stress analysis is one of the most important processes in designing an underground excavation. With the usage of numerical methods on a computer, such as the Boundary Element Method (BEM), the process of stress analysis can be made accurate. However, the computational implementation of stress analysis often requires considerable time and computational resources. For example, in the implementation of BEM, the finer the computational grid is, the longer time will take to compute the results. Based on the research of GPU-accelerated stress analysis in geomechanics (Zsaki, 2011), this thesis investigates one type of acceleration method, which used the parallel computing ability of modern graphics processing units (GPUs), for application to the traditional BEM algorithm. In this thesis, OpenCL was used as the framework to compile and execute programs on GPUs. By transferring and executing the most computational expensive parts of the traditional BEM code onto GPU, a respectable acceleration was achieved. Subsequently, with the application of a two-dimensional circular excavation example, the accuracy of the BEM algorithm implementation on a GPU was verified for both single-precision and double-precision calculations. In addition, two more excavation examples were taken into consideration to assess the accuracy and reduction in solution time. The performance for these three examples successfully verified the GPU-accelerating method and displayed an impressive acceleration effect with the speedup ratio of about 500 for single-precision and 15 for double-precision

Miamia maimai n. sp., a new Pennsylvanian stem-orthopteran insect, and a case study on the application of cladotypic nomenclature

A new stem-orthopteran insect assignable to the – traditional – genus and the – cladotypic-defined – taxon Miamia Dana, 1864 is described based on abundant material collected from the Xiaheyan locality (Ningxia, China; Early Pennsylvanian). Intra-specific wing venation variability in Miamia maimai n. sp. is appreciated based on wing pairs of single individuals, and on a complete series of conditions. Rare variants are reported. Details of head and leg morphology are documented: the new species possesses a five-segmented tarsus provided with paired claws and arolium, and labial palps with at least four segments, probably five. The nomenclatural section is conducted under the cladotypic nomenclatural procedure, but in a way largely consistent with the traditional usage. This experiment demonstrates that a combination composed of a "genus level-taxon" name previously associated with a definition and type material (e.g. Miamia), a specific epithet (e.g. maimai), and authorship information (e.g. Béthoux et al. 2012), with further mention to "Miamia maimai" or "M. maimai", provides a suitable reference to the species under all nomenclatural procedures, including the traditional one.doi:10.1002/mmng.20120000