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The past decade of ZERODUR® glass-ceramics in space applications
No full textFor the past four decades, ZERODUR® glass ceramics has flown on many satellites including the prominent
space missions METEOSAT, Hubble Space Telescope, CHANDRA, and LISA pathfinder. Firstly, this unique
material is chosen as mirror substrate for high precision optics due to its extreme thermal stability. Its near-zero thermal expansion over a wide temperature range of several tens of Kelvin is homogenous within the entire
volume. This enables control of the ZERODUR®’s surface profile at the 10-picometer level. SCHOTT has conducted comprehensive material characteristics studies on the mechanical properties and the radiation environment effects experienced in realistic orbits to define the suitability of ZERODUR® to survive both high loads during launch and to support long-term missions, respectively.
Besides these advantageous material properties, this glass-ceramics can be extremely light-weighted by
precision grinding enabled by the new SCHOTT competence center for machining and metrology. In this paper,
we will continue to trace the recent developments of ZERODUR® glass ceramics as space material in the context
of selected missions flown since 2009 and those anticipated. Major milestones such as the LISA pathfinder
mission are discussed. Furthermore, we outline the viable use of ZERODUR® for great observatory
architectures for IR/O/UV spaceborne telescopes.
The objective of this paper is to supplement an earlier review of the use of ZERODUR® for space applications
in the past decade and to summarize the latest progress and results of material studies toward very efficient
production capabilities for high-performance light-weighted mirror substrates
EEG functional connectivity and deep learning for automatic diagnosis of brain disorders: Alzheimer’s disease and schizophrenia
No full textMental disorders are among the leading causes of disability worldwide. The first step in treating
these conditions is to obtain an accurate diagnosis. Machine learning algorithms can provide a
possible solution to this problem, as we describe in this work. We present a method for the
automatic diagnosis of mental disorders based on the matrix of connections obtained from EEG
time series and deep learning. We show that our approach can classify patients with Alzheimer’s
disease and schizophrenia with a high level of accuracy. The comparison with the traditional cases,
that use raw EEG time series, shows that our method provides the highest precision. Therefore, the
application of deep neural networks on data from brain connections is a very promising method
for the diagnosis of neurological disorders
Effective areas of astronomical X-ray optics for cubesats and rocket experiments
No full textThe effective area is one of the main telescope parameters when justifying real space application. We discuss the estimation of the effective collecting area of an X-ray telescope by two different methods, an analytical method and a simulation algorithm, and then compare the results. The Lobster Eye type telescopes considered here are designed for rocket experiments and CubeSat flights
Cryovolcanism in the Solar System and beyond: Considerations on Energy Sources, Geological Aspects, and Astrobiological Perspectives
No full textVolcanism based on melting rocks (silicate volcanism) is long known on Earth and has also been found on Jupiter’s moon Io. Remnants of this type of volcanism have been identified also on other bodies in the solar system. Energy sources powered by accretion and the decay of radioactive isotopes seem to be dominant mainly inside larger bodies, which have enough volume to accumulate and retain this energy in significant amounts. On the other hand, the impact of tidal forces allows even tiny bodies to melt up and pass into the stage of cryovolcanism. The dependence of tidal heating on the size of the object is minor, but the masses of and the distances to accompanying bodies as well as the inner compositions of the heated body are central factors. Even though Io as an example of a body supporting silicate volcanism is striking, the physics of tidal forces might suggest a relatively high probability for cryovolcanism. This chapter aims at considering the parameters known and objects found so far in our solar system to give insights into where in our system and other planetary systems cryovolcanism might be expected
Enterprise Social Media and Control System Design
No full textEnterprise social media has been found to be a curse and a blessing at the same time. ESM has been reported to lead to unproductive ‘games of visibility’ and ‘exhibitionism’, while it has been also found to enable productive outcomes related to knowledge work and product innovation, the latter being the main reason for its wide-spread adoption. We argue that decisions to use ESM as a control instrument are not made in isolation, but as part of a set of complementary choices. We provide arguments and empirical evidence that the use of ESM as a control instrument in organizations complements the use of subjective evaluations of non-task related performance (SPE). We also show that firms that face high ESM employee concerns, have a stronger complementarity between ESM use and SPE. Additional analyses show that ESM use and performance-based pay (PBP) are also complements. Together the results imply that management control system configuration changes with the employment of ESM
High Frequency Power Amplifier for Wideband Wireless Communication Systems
No full textIncreasing data transmission rates and bandwidth both belong to the challenges of the development of high-performance wireless communication systems. Multi-channel communication systems commonly use several narrowband power amplifiers each one for a single communication channel. Lossy couplers are needed both to separate the different channels from each other at the amplifiers input and to combine the amplified signals on each channel at the output. This approach depicts a poor efficiency and is limited to a few number of channels since each channel duplication involves 3 dB losses due to couplers.
Alternatively, broadband radio frequency power amplifiers ensuring the simultaneous transmission of several carriers on a wide frequency range contribute to increase the cost and resource efficiency of transceivers in wireless communication systems. Gain flatness, a high output power, and low power levels of second and third order harmonics are required on the whole operating frequency range of the power amplifier in multi-carrier communication systems since overtones will degrade the quality of the communication.
The present work investigates the performances of a broadband push-pull power amplifier based on LDMOS transistors, the input matching network using a 8:1 transmission line transformer. For the first time investigations on harmonic distortions of the amplified signal when using a transformer with 8:1 impedance transformation ratio are presented. Characterisation of the power amplifiers performances is focused on gain flatness, output power, harmonic distortions and efficiency at 110 W