Astronomical Distance Determination in the Space Age: Secondary Distance Indicators

The formal division of the distance indicators into primary and secondary leads to difficulties in description of methods which can actually be used in two ways: with, and without the support of the other methods for scaling. Thus instead of concentrating on the scaling requirement we concentrate on all methods of distance determination to extragalactic sources which are designated, at least formally, to use for individual sources. Among those, the Supernovae Ia is clearly the leader due to its enormous success in determination of the expansion rate of the Universe. However, new methods are rapidly developing, and there is also a progress in more traditional methods. We give a general overview of the methods but we mostly concentrate on the most recent developments in each field, and future expectations. © 2018, The Author(s)

Strength testing of hot gas filters: Volume 6. Final report

The strength of various ceramic hot gas filter materials has been evaluated by four laboratories: Argonne National Laboratory, DuPont Lanxide, Southern Research Institute and Babcock and Wilcox. The filter materials under study include (a) a Nextel{trademark}/SiC composite filter (from 3M), (b) PRD-66, an all oxide layered microstructure of alumina, mullite, cordierite and some amorphous material by DuPont Lanxide, (c) a Babcock and Wilcox material consisting of an oxide composite of chopped fibers (Saffil) and continuous Nextel fibers, (d-f) monolithic and recrystallized SiC materials and an alumino/aluminosilicate material by IFPM, and (g) a monolithic SiC by the Pall Corporation. Not all four organizations tested each of the materials. PRD-66 was tested by three of the four. Four tests were used to evaluate properties of the candle filter materials. They included (a) the C-ring test, (b) the O-ring test, (c) the burst test and (d) the axial compression test. Each organization identified above did not perform all four tests. The objective of the study described here was to (a) provide an evaluation of the test methods used for hot gas filters to determine which is best for hot gas filter evaluation and (b) evaluate the discrepancies in results from tests run at different laboratories. No material ranking was made here, nor requested

The effect of aggregate aspect ratio and temperature on the fracture toughness of a low cement refractory concrete

This work investigated the influence of the aggregate's aspect ratio on the fracture behavior of a low cement aluminum silicate refractory castable treated at two different temperatures (110 °C and 1000 °C). The aggregates were cylindrical pellets with an aspect ratio of 1, 2, 3 and 4, produced by extruding a mixture of clay and calcined alumina fired at 1600 °C for 4 h to yield mullite (3Al2O3.2SiO2). The behavior of the R-Curve and other relevant fracture parameters were evaluated based on the "Two Parameter Fracture Model" in a three-point flexure test of single-edge straight through notched specimens. The two temperature treatments produced different degrees of matrix-aggregate adhesion. The larger aspect ratio aggregates were found to promote toughening only in the dried condition, at 110 °C, while the specimens fired at 1000 °C for 4 h, regardless of their aggregate aspect ratio, displayed no significant toughening. The best results for fired samples, however, were obtained from specimens containing conventional angular aggregates

Load partitioning in honeycomb-like silicon carbide aluminum alloy composites

A 50/50 vol.% Al/SiC composite was made via melt infiltration of an aluminum alloy into a porous beech wood-derived SiC preform. The honeycomb-like composite microstructure consisted of an interconnected SiC phase surrounding discrete Al “fibers” aligned in the growth direction of the beech wood. High energy synchrotron X-ray diffraction was used to measure the volume averaged lattice strains in both the SiC and Al phases during in situ compressive loading up to an applied stress of −530 MPa. Load transfer from the Al to the SiC was observed, and the Al yielded at an applied stress of above −213 MPa. The elastic behavior of the composite was modeled with both an isostrain rule of mixtures calculation and variational bounds for the effective elastic modulus. Furthermore, calculations of the von Mises effective stress of the SiC and Al phases showed that the wood-derived SiC was a more effective reinforcement than either SiC particle- or whisker-reinforced composites