SIMULATION-BASED EVALUATION OF RESERVATION MECHANISMS FOR THE TIME WINDOW ROUTING METHOD

Automated warehouses operated by a fleet of robots offer great flexibility, since fleet size can be adjusted easily to throughput requirements. Furthermore, they provide higher redundancy compared to common solutions for automated storage and retrieval systems.On the other hand, these systems require more complex control strategies to run robustly and efficiently. Special routing and deadlock handling strategies are necessary to avoid blocking and collisions among the robots.In this contribution, we focus on the time window routing method, an approach for avoiding deadlocks byreserving routes in advance. We present and discussdifferent reservation mechanisms that are evaluated bythe means of simulation.Automated warehouses operated by a fleet of robots offer great flexibility, since fleet size can be adjusted easily to throughput requirements. Furthermore, they provide higher redundancy compared to common solutions for automated storage and retrieval systems. On the other hand, these systems require more complex control strategies to run robustly and efficiently. Special routing and deadlock handling strategies are necessary to avoid blocking and collisions among the robots. In this contribution, we focus on the time window routing method, an approach for avoiding deadlocks by reserving routes in advance. We present and discuss different reservation mechanisms that are evaluated by the means of simulation

Changing disc compositions via internal photoevaporation

The chemical evolution of protoplanetary discs is not fully understood, several factors influence the final distribution of disc material. One such factor are inward drifting and evaporating pebbles that enrich the inner disc with vapour. In particular, it is first enriched with water vapour, resulting in a low C/O ratio, before carbon-rich gas from the outer disc is transported inwards elevating the C/O ratio again. However, it is unclear how internal photoevaporation, which carries away gas and opens gaps that block inward drifting pebbles, affects the chemical composition of the disc. We aim to study these effects in discs around solar-like stars, where we especially focus on the C/O ratio and the water content. The simulations are carried out using a semi-analytical 1D disc model. Our code chemcomp includes viscous evolution and heating, pebble growth and drift, pebble evaporation and condensation, and a simple chemical partitioning model. We show that internal photoevaporation plays a major role in the (chemical) evolution of protoplanetary discs: As it opens a gap, inward drifting pebbles are stopped and cannot contribute to the volatile content any more. In addition, gas from the outer disc is carried away by photoevaporative winds. Consequently, the C/O ratio in the inner disc is low. In contrast, gaps opened by giant planets allow the gas to pass, resulting in an elevated C/O ratio, similar to viscous discs without internal photoevaporation. This will enable us to distinguish observationally between these two scenarios when measuring the C/O ratio, implying that we can infer the cause of gap structures in disc observations. In the case of a photoevaporative disc, we additionally find an elevated water content in the inner disc as the water vapour and ice undergo a cycle of evaporation/re-condensation, preventing its inward accretion onto the star

Characterization of Irradiation Damage Using X-Ray Diffraction Line-Profile Analysis

During operation, structural components made of zirconium alloys are subject toneutron irradiation, which leads to the displacement of zirconium atoms fromtheir lattice sites, the production of self-interstitials and vacancies, and eventually dislocation loops. This process can lead to deleterious effects such as irradiation growth, creep, and embrittlement as well as accelerated aqueous corrosion. Quantitative analysis of dislocation line densities is seen as an importantpathway for distinguishing between the irradiation response of different alloys.The analysis of irradiation damage using X-ray diffraction (XRD) line-profile analysis has proven to be a powerful complementary technique to transmissionelectron microscopy, which samples a comparatively large volume and is lessaffected by the subjectivity of image analysis. In this paper we present andanalyze three different types of XRD experiments, describing their purpose andthe new insight achieved using each technique. First, we present work carriedout on neutron-irradiated samples, comparing dislocation line densities measured by XRD with macroscopic growth measurements. A second experimentusing a synchrotron-based X-ray microbeam enabled the mapping of dislocationline densities as a function of depth from the surface of proton-irradiated zirconium alloys. These data are compared with calculated damage profiles, providingnew insight into the early saturation of damage. Finally, the last example presented here focuses on synchrotron-based 3D XRD measurements, for whichdislocation-loop line densities were analyzed in hundreds of individual grains,providing excellent statistics about the grain-to-grain variability of line densities

Attitudes toward westbound refugees in the East German press

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67107/2/10.1177_002200277001400303.pd

Advancements in decadal climate predictability: the role of nonoceanic drivers

We review recent progress in understanding the role of sea ice, land surface, stratosphere, and aerosols in decadal-scale predictability and discuss the perspectives for improving the predictive capabilities of current Earth system models (ESMs). These constituents have received relatively little attention because their contribution to the slow climatic manifold is controversial in comparison to that of the large heat capacity of the oceans. Furthermore, their initialization as well as their representation in state-of-the-art climate models remains a challenge. Numerous extraoceanic processes that could be active over the decadal range are proposed. Potential predictability associated with the aforementioned, poorly represented, and scarcely observed constituents of the climate system has been primarily inspected through numerical simulations performed under idealized experimental settings. The impact, however, on practical decadal predictions, conducted with realistically initialized full-fledged climate models, is still largely unexploited. Enhancing initial-value predictability through an improved model initialization appears to be a viable option for land surface, sea ice, and, marginally, the stratosphere. Similarly, capturing future aerosol emission storylines might lead to an improved representation of both global and regional short-term climatic changes. In addition to these factors, a key role on the overall predictive ability of ESMs is expected to be played by an accurate representation of processes associated with specific components of the climate system. These act as “signal carriers,” transferring across the climatic phase space the information associated with the initial state and boundary forcings, and dynamically bridging different (otherwise unconnected) subsystems. Through this mechanism, Earth system components trigger low-frequency variability modes, thus extending the predictability beyond the seasonal scale

Rock magnetism and the interpretation of anisotropy of magnetic susceptibility

CNR