Channel Protection: Random Coding Meets Sparse Channels

Multipath interference is an ubiquitous phenomenon in modern communication systems. The conventional way to compensate for this effect is to equalize the channel by estimating its impulse response by transmitting a set of training symbols. The primary drawback to this type of approach is that it can be unreliable if the channel is changing rapidly. In this paper, we show that randomly encoding the signal can protect it against channel uncertainty when the channel is sparse. Before transmission, the signal is mapped into a slightly longer codeword using a random matrix. From the received signal, we are able to simultaneously estimate the channel and recover the transmitted signal. We discuss two schemes for the recovery. Both of them exploit the sparsity of the underlying channel. We show that if the channel impulse response is sufficiently sparse, the transmitted signal can be recovered reliably.Comment: To appear in the proceedings of the 2009 IEEE Information Theory Workshop (Taormina

Passiv damping on spacecraft sandwich panels

For reusable and expendable launch vehicles as well as for other spacecraft structural vibration loads are safety critical design drivers impacting mass and lifetime. Here, the improvement of reliability and safety, the reduction of mass, the extension of service life, as well as the reduction of cost for manufacturing are desired. Spacecraft structural design in general is a compromise between lightweight design and robustness with regard to dynamic loads. The structural stresses and strains due to displacements caused by dynamic loads can be reduced by mechanical damping based on passive or active measures. Passive damping systems can be relatively simple and yet are capable of suppressing a wide range of mechanical vibrations. Concepts are low priced in development, manufacturing and application as well as maintenancefree. Compared to active damping measures passive elements do not require electronics, control algorithms, power, actuators, sensors as well as complex maintenance. Moreover, a reliable application of active dampers for higher temperatures and short response times (e. g. re-entry environment) is questionable. The physical effect of passive dampers is based on the dissipation of load induced energy. Recent activities performed by OHB have shown the function of a passive friction-damping device for a vertical tail model of the German X-vehicle PHÖNIX but also for general sandwich structures. The present paper shows brand new results from a corresponding ESA-funded activity where passive damping elements are placed between the face sheets of large spacecraft relevant composite sandwich panels to demonstrate dynamic load reduction in vibration experiments on a shaker. Several passive damping measures are investigated and compared

VELOX – A Demonstration Facilility for Lunar Oxygen Extraction in a Laboratory Environment

The ultimate goal of a permanent human presence on the Moon is discussed intensively within the global lunar community. Obviously, such an effort poses stringent demands not only on the technology but also on logistics, especially considering the important aspects of masses and volume for materials and replenishments of consumables. On-site propellant production (i.e. liquid oxygen) is one of the main needs and would lead to more efficient return-to-Earth or further exploration missions. Additionally, the supply of breathable air and water for the survival of the crew on the lunar surface is also a major aspect. Thus, large effort is put into the development and research of technologies for in-situ resources utilization (ISRU) to drastically reduce the required supply from Earth and to increase the level of autonomy of a lunar outpost. The major resource on the Moon for such a purpose is regolith, which covers the first meters of the lunar surface and contains about 45% of mineralogically bounded Oxygen in terms of mass. By using adequate processing methods of this material, one could be able to extract valuable minerals and volatiles for further utilization. At DLR Bremen a compact and flexible lab experimenting facility has been developed, built and tested, which shall demonstrate the feasibility of the process by extracting oxygen out of lunar regolith, respectively soil simulants and certain minerals in the laboratory case. For this purpose, important boundary conditions have been investigated such as temperatures during the process, chemical reaction characteristics and material properties for the buildup of the facility, which shall be analyzed within this paper. Since it is one of the most elaborated chemical processes regarding ISRU and has comparably low temperature and energy constraints it has been primarily concentrated on the Hydrogen-reduction process which reduces the iron oxide component of Ilmenite (FeTiO3) within the lunar regolith. Based on the obtained results, a first line-out of a planned superior test set-up and infrastructure with pre- and post-processing units such as feeding and extraction is also presented, as well as an analysis of reaction products with common methods. This paper will present the first results of DLR efforts regarding these topics. Finally, important aspects of the future development of the processes and technologies are discussed with special consideration of lunar applicability and with respect to environmental conditions as well as mass and energy constraints

Information Extraction From Chemical Patents

The development of new chemicals or pharmaceuticals is preceded by an indepth analysis of published patents in this field. This information retrieval is a costly and time inefficient step when done by a human reader, yet it is mandatory for potential success of an investment. The goal of the research project UIMA-HPC is to automate and hence speed-up the process of knowledge mining about patents. Multi-threaded analysis engines, developed according to UIMA (Unstructured Information Management Architecture) standards, process texts and images in thousands of documents in parallel. UNICORE (UNiform Interface to COmputing Resources) workflow control structures make it possible to dynamically allocate resources for every given task to gain best cpu-time/realtime ratios in an HPC environment

Impaired object-location learning and recognition memory but enhanced sustained attention in M2 muscarinic receptor-deficient mice

© 2018, The Author(s). Rationale: Muscarinic acetylcholine receptors are known to play key roles in mediating cognitive processes, and impaired muscarinic cholinergic neurotransmission is associated with normal ageing processes and Alzheimer’s disease. However, the specific contributions of the individual muscarinic receptor subtypes (M1–M5) to cognition are presently not well understood. Objectives: The aim of this study was to investigate the contribution of M2-type muscarinic receptor signalling to sustained attention, executive control and learning and memory. Methods: M2 receptor-deficient (M2−/−) mice were tested on a touchscreen-operated task battery testing visual discrimination, behavioural flexibility, object-location associative learning, attention and response control. Spontaneous recognition memory for real-world objects was also assessed. Results: We found that M2−/− mice showed an enhancement of attentional performance, but significant deficits on some tests of learning and memory. Executive control and visual discrimination were unaffected by M2-depletion. Conclusions: These findings suggest that M2 activation has heterogeneous effects across cognitive domains, and provide insights into how acetylcholine may support multiple specific cognitive processes through functionally distinct cholinergic receptor subtypes. They also suggest that therapeutics involving M2 receptor-active compounds should be assessed across a broad range of cognitive domains, as they may enhance some cognitive functions, but impair others

The token’s secret: the two-faced financial incentive of the token economy

Multi-sided platforms are omnipresent in today’s digital world. However, establishing a platform includes challenges: The platform utility usually increases with the number of participants. At an early stage, potential participants expect the platform utility to be low and lack an incentive to join (i.e., “chicken and egg” problem). Blockchain-enabled utility tokens hold the promise to overcome this problem. They supposedly provide a suitable financial incentive for their owners to join the platform as soon as possible. In the first half of 2018, investors seemed to believe in the presumption and spent more than US$ 17.6 billion in token sales. To date, we know little about this financial incentive in the context of the token economy. For this purpose, we model the token value development and the associated incentives in a multi-sided blockchain-enabled platform. The resulting findings suggest that blockchain-enabled utility tokens can help to overcome the “chicken and egg” problem. However, these tokens lead to contradictory incentives for platform participants, and can even inhibit platform usage. The contribution of our work is twofold: First, we develop one of the first models for token value development. Second, our research contributes to a deeper understanding of the utility token’s financial incentive