We present an approach to testing the gravitational redshift effect using the RadioAstron satellite. The experiment is based on a modification of the Gravity Probe A scheme of nonrelativistic Doppler compensation and benefits from the highly eccentric orbit and ultra-stable atomic hydrogen maser frequency standard of the RadioAstron satellite. Using the presented techniques we expect to reach an accuracy of the gravitational redshift test of order 10-5, a magnitude better than that of Gravity Probe A. Data processing is ongoing, our preliminary results agree with the validity of the Einstein Equivalence Principle.

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A test of a cornerstone of general relativity, the gravitational redshift effect, is currently being conducted with the RadioAstron spacecraft, which is on a highly eccentric orbit around Earth. Using ground radio telescopes to record the spacecraft signal, synchronized to its ultra-stable on-board H-maser, we can probe the varying flow of time on board with unprecedented accuracy. The observations performed so far, currently being analyzed, have already allowed us to measure the effect with a relative accuracy of 4 × 10−4 . We expect to reach 2.5×10−5 with additional observations in 2016, an improvement of almost a magnitude over the 40-year old result of the GP-A mission.@en

Context. The closest ever fly-by of the Martian moon Phobos, performed by the European Space Agency's Mars Express spacecraft, gives a unique opportunity to sharpen and test the Planetary Radio Interferometry and Doppler Experiments (PRIDE) technique in the interest of studying planet-satellite systems. Aims. The aim of this work is to demonstrate a technique of providing high precision positional and Doppler measurements of planetary spacecraft using the Mars Express spacecraft. The technique will be used in the framework of Planetary Radio Interferometry and Doppler Experiments in various planetary missions, in particular in fly-by mode. Methods. We advanced a novel approach to spacecraft data processing using the techniques of Doppler and phase-referenced very long baseline interferometry spacecraft tracking. Results. We achieved, on average, mHz precision (30 μm/s at a 10 s integration time) for radial three-way Doppler estimates and sub-nanoradian precision for lateral position measurements, which in a linear measure (at a distance of 1.4 AU) corresponds to ∼50 m.

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Knowledge of failure strength is the key to structural glass applications. However, the influence of the manufacturing process on the failure initiation at the glass edge is not well known. For this paper, small-scale glass specimens are tested in four-point bending, creating tensile stresses at the glass edge. Several edge finishings are investigated and their flaws detected concentrating on the failure initiating flaw. The characteristics of glass edge machining flaws are estimated by comparing obtained experimental values to existing time-dependent strength theory described in fracture mechanics. As a conclusion, typical edge flaws in industrial glass edge finishings are characterized and used as a basis for glass failure strength estimations.@en

The present work focuses on stress-corrosion mechanisms in soda-lime silica glass. Four-point beam-bending tests were performed on small specimens, measuring failure time in function of temperature and relative humidity. By using linear elastic fracture mechanics, average velocity of edge flaws propagation was evaluated as a function of stress intensity factor, allowing a comparison with experimental curves from the literature. Experimental results are consistent with the main stress-corrosion theories and with chemical kinetics equation for a general reaction. Also, by using a crack evolution power-law and an equivalence relation for constant stress, we have compared our results with lifetime curves relative to environmental conditions of the tests.@en

In modern buildings, glass is increasingly used as a load-carrying material in structural components, such as glass beams. For glass beams especially the edge strength of glass is important. However, the strength of glass is not a material constant but depends on various parameters, which makes glass, amongst other things, a challenging building material. One of the parameters influencing glass strength is the combination of humidity and stress, which may cause stress corrosion. The aim of the current study is to limit the effect of humidity at the glass edge. This is done by the application of a protective coating. In this exploratory study several coating solutions are tested applying the coating at the edge of glass specimens. These specimens are then subjected to in-plane four-point bending tests to determine their failure strength. The effects of the coatings on the edge strength are analyzed using the failure strength data from the bending tests. The results indicate that only one of the tested coatings has an effect on the glass edge strength.@en

For the past three decades, glass has become more frequently used for secondary construction elements in façade glazing, as well as for structural elements. In the latter case, the edge strength becomes an important issue when designing a structural glass beam or a façade fin. Different parameters affect the edge strength of glass, such as 1) the type of edge finishing and the supplier, 2) the size of the element and 3) the load duration. The first parameter affects the number and the shape of the edge flaws caused by cutting or polishing the edge. Secondly, the size effect is important because larger elements tend to have a greater probability of larger flaws. Finally, the load duration has an impact on the time-dependent strength. In this study, 16 series of glass specimens with different edge finishings and sizes were subjected to in-plane four-point bending tests at several loading rates. The environmental effect (i.e. humidity) was not examined, as all the tests were carried out under constant laboratory conditions. After comparing different distributions, the most appropriate distribution, i.e. Weibull, was used. The results of the series were compared statistically relative to the parameters mentioned above. The results indicate large variations in the edge strength, which are assumed to be related to the edge finishing and the glass supplier. A detailed manufacturing protocol is needed for a more accurate comparison of the results. Furthermore, unlike the size effect, the load duration effect was found to comply with earlier results given in literature.@en