Many asteroids and trans-neptunian objects have satellites: the tally stands at over 150 on http://tinyurl.com/dweqf
 . The smallest of these binary systems are main-belt and near-Earth asteroids, but the environments of these two types of object are very different, making it difficult to work out a common mechanism to explain their formation. Now Walsh et al. present a model that fits the bill. Properties of the observed main-belt and near-Earth asteroids with satellites are matched by simulations involving the slow spinup of a 'rubble pile' asteroid via the thermal YORP effect (where radiation from an irregular body exerts a net force on that body). The mass shed from the equator of a spinning body accretes into a satellite if the material consists of particles undergoing energy-dissipating collisions. Binary asteroids are created by the slow spin up of a 'rubble pile' asteroid via the thermal YORP effect (where radiation from an irregularly shaped body exerts a net force on the body). The mass shed from the equator of a critically spinning body accretes into a satellite if the material is collisionally dissipative. Asteroids with satellites are observed throughout the Solar System, from subkilometre near-Earth asteroid pairs to systems of large and distant bodies in the Kuiper belt. The smallest and closest systems are found among the near-Earth and small inner main-belt asteroids, which typically have rapidly rotating primaries and close secondaries on circular orbits. About 15 per cent of near-Earth and main-belt asteroids with diameters under 10 km have satellites1,2. The mechanism that forms such similar binaries in these two dynamically different populations was hitherto unclear. Here we show that these binaries are created by the slow spinup of a ‘rubble pile’ asteroid by means of the thermal YORP (Yarkovsky–O’Keefe–Radzievskii–Paddack) effect. We find that mass shed from the equator of a critically spinning body accretes into a satellite if the material is collisionally dissipative and the primary maintains a low equatorial elongation. The satellite forms mostly from material originating near the primary’s surface and enters into a close, low-eccentricity orbit. The properties of binaries produced by our model match those currently observed in the small near-Earth and main-belt asteroid populations, including 1999 KW4 (refs 3, 4).

Rotational Breakup as the Origin of Small Binary Asteroids

Chemical Quality of Water and the Hydrologic Cycle

This survey provides an overview of the scientific literature on timing verification techniques for multi-core real-time systems. It reviews the key results in the field from its origins around 2006 to the latest research published up to the end of 2018. The survey highlights the key issues involved in providing guarantees of timing correctness for multi-core systems. A detailed review is provided covering four main categories: full integration, temporal isolation, integrating interference effects into schedulability analysis, and mapping and allocation. The survey concludes with a discussion of the advantages and disadvantages of these different approaches, identifying open issues, key challenges, and possible directions for future research.

/pdf/a-survey-of-timing-verification-techniques-for-multi-core-24udidwr5p.pdf

A Survey of Timing Verification Techniques for Multi-Core Real-Time Systems

Many-core processors offer massively parallel computation power representing a good opportunity for the design of highly integrated avionics systems. Such designs must face several challenges among which 1) temporal isolation must be ensured between applications and 2) bounds of WCET must be computed for real-time safety critical applications. In order to partially address those issues, we propose an appropriate execution model, that restricts the applications behaviours, which has been implemented on the Kalray MPPA-256. We tested the correctness of the approach through a series of benchmarks and the implementation of a case study.

/pdf/temporal-isolation-of-hard-real-time-applications-on-many-4iiop9s07z.pdf

Temporal Isolation of Hard Real-Time Applications on Many-Core Processors

Characteristic temperatures and structural relaxation times for different classes of glass-forming polymer liquids are computed using a revised entropy theory of glass formation that permits the chain backbone and the side groups to have different rigidities. The theory is applied to glass formation at constant pressure or constant temperature. Our calculations provide new insights into physical factors influencing the breadth of the glass transition and the associated growth of relaxation times.

/pdf/direct-computation-of-characteristic-temperatures-and-1oh75rmt2x.pdf

Direct Computation of Characteristic Temperatures and Relaxation Times for Glass-Forming Polymer Liquids

Many-core processors are interesting candidates for the design of modern avionics computers. Indeed, the computational power offered by such platforms opens new horizons to design more demanding systems and to integrate more applications on a single target. However, they also bring challenging research topics because of their lack of predictability and their programming complexity. In this paper, we focus on the problem of mapping large applications on a complex platform such as the KALRAY MPPA®-256 while maintaining a strong temporal isolation from co-running applications. We propose a constraint programming formulation of the mapping problem that enables an efficient parallelization and we demonstrate the ability of our approach to deal with large problems using a real world case study.

/pdf/mapping-hard-real-time-applications-on-many-core-processors-46s14l32en.pdf

Mapping hard real-time applications on many-core processors

The use of many-core COTS processors in safety critical embedded systems is a challenging research topic. The predictable execution of several applications on those processors is not possible without a precise analysis and mitigation of the possible sources of interference. In this paper, we identify the external DDR-SDRAM and the Network on Chip to be the main bottlenecks for both average performance and predictability in such platforms. As DDR-SDRAM memories are intrinsically stateful, the naive calculation of the Worst-Case Execution Times (WCETs) of tasks involves a significantly pessimistic upper-bounding of the memory access latencies. Moreover, the worst-case end-to-end delays of wormhole switched networks cannot be bounded without strong assumptions on the system model because of the possibility of deadlock. We provide an analysis of each potential source of interference and we give recommendations in order to build viable execution models enabling efficient composable computation of worst-case end-to-end memory access latencies compared to the naive worst-case-everywhere approach.

https://hal.archives-ouvertes.fr/hal-01256000/document

Predictable composition of memory accesses on many-core processors

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Temporal Isolation of Hard Real-Time Applications on Many-Core Processors

Mapping hard real-time applications on many-core processors

Predictable composition of memory accesses on many-core processors