Emergence of spatio-temporal dynamics from exact coherent solutions in pipe flow

Turbulent-laminar patterns are ubiquitous near transition in wall-bounded shear flows. Despite recent progress in describing their dynamics in analogy to non-equilibrium phase transitions, there is no theory explaining their emergence. Dynamical-system approaches suggest that invariant solutions to the Navier–Stokes equations, such as traveling waves and relative periodic orbits in pipe flow, act as building blocks of the disordered dynamics. While recent studies have shown how transient chaos arises from such solutions, the ensuing dynamics lacks the strong fluctuations in size, shape and speed of the turbulent spots observed in experiments. We here show that chaotic spots with distinct dynamical and kinematic properties merge in phase space and give rise to the enhanced spatio-temporal patterns observed in pipe flow. This paves the way for a dynamical-system foundation to the phenomenology of turbulent-laminar patterns in wall-bounded extended shear flows.Peer ReviewedPostprint (published version

QoS in the Linux operating system

This document describes the implementation of our QoS architecture, which has been developed in the context of our UNIQuE project. In order to achieve an end-to-end quality of service, our approach bases on feedback loops. Therefore, the basis is an adaptive CPU scheduler, which is a key element in our QoS architecture. We used the Linux Operating System (version 2.3.49 as the QoS architecture requires modifications in the kernel mechanisms and the sources of Linux are available

Thermal Fingerprinting—Multi-Dimensional Analysis of Computational Loads

Digital fingerprinting is used in several domains to identify and track variable activities and processes. In this paper, we propose a novel approach to categorize and recognize computational tasks based on thermal system information. The concept focuses on all kinds of data center environments to control required cooling capacity dynamically. The concept monitors basic thermal sensor data from each server and chassis entity. The respective, characteristic curves are merged with additional general system information, such as CPU load behavior, memory usage, and I/O characteristics. This results in two-dimensional thermal fingerprints, which are unique and achievable. The fingerprints are used as input for an adaptive, pre-active air-conditioning control system. This allows a precise estimation of the data center health status. First test cases and reference scenarios clarify a huge potential for energy savings without any negative aspects regarding health status or durability. In consequence, we provide a cost-efficient, light-weight, and flexible solution to optimize the energy-efficiency for a huge number of existing, conventional data center environments

ReAFFIRM: Real-time Assessment of Flash Flood Impacts: a Regional high-resolution Method

Flash floods evolve rapidly in time, which poses particular challenges to emergency managers. One way to support decision-making is to complement models that estimate the flash flood hazard (e.g. discharge or return period) with tools that directly translate the hazard into the expected socio-economic impacts. This paper presents a method named ReAFFIRM that uses gridded rainfall estimates to assess in real time the flash flood hazard and translate it into the corresponding impacts. In contrast to other studies that mainly focus on in- dividual river catchments, the approach allows for monitoring entire regions at high resolution. The method consists of the following three components: (i) an already existing hazard module that processes the rainfall into values of exceeded return period in the drainage network, (ii) a flood map module that employs the flood maps created within the EU Floods Directive to convert the return periods into the expected flooded areas and flood depths, and (iii) an impact assessment module that combines the flood depths with several layers of socio- economic exposure and vulnerability. Impacts are estimated in three quantitative categories: population in the flooded area, economic losses, and affected critical infrastructures. The performance of ReAFFIRM is shown by applying it in the region of Catalonia (NE Spain) for three significant flash flood events. The results show that the method is capable of identifying areas where the flash floods caused the highest impacts, while some locations affected by less significant impacts were missed. In the locations where the flood extent corresponded to flood observations, the assessments of the population in the flooded area and affected critical infrastructures seemed to perform reasonably well, whereas the economic losses were systematically overestimated. The effects of different sources of uncertainty have been discussed: from the estimation of the hazard to its translation into impacts, which highly depends on the quality of the employed datasets, and in particular on the quality of the rainfall inputs and the comprehensiveness of the flood maps.Peer ReviewedPostprint (published version

Phononic filter effect of rattling phonons in the thermoelectric clathrate Ba8_8Ge40+x_{40+x}Ni6−x_{6-x}

One of the key requirements for good thermoelectric materials is a low lattice thermal conductivity. Here we present a combined neutron scattering and theoretical investigation of the lattice dynamics in the type I clathrate system Ba-Ge-Ni, which fulfills this requirement. We observe a strong hybridization between phonons of the Ba guest atoms and acoustic phonons of the Ge-Ni host structure over a wide region of the Brillouin zone which is in contrast with the frequently adopted picture of isolated Ba atoms in Ge-Ni host cages. It occurs without a strong decrease of the acoustic phonon lifetime which contradicts the usual assumption of strong anharmonic phonon--phonon scattering processes. Within the framework of ab-intio density functional theory calculations we interpret these hybridizations as a series of an ti-crossings which act as a low pass filter, preventing the propagation of acoustic phonons. To highlight the effect of such a phononic low pass filter on the thermal transport, we compute the contribution of acoustic phonons to the thermal conductivity of Ba$_8$Ge$_{40}$Ni$_{6}$ and compare it to those of pure Ge and a Ge$_{46}$ empty-cage model system.Comment: 10 pages, 10 figure

Concurrent Parasitism Alters Thermoregulation in Honey Bee (Hymenoptera: Apidae) Winter Clusters

Thermoregulation is crucial for honey bee, Apis mellifera L. (Hymenoptera: Apidae), colony survival in temperate regions, but possible interference by parasites is currently unknown. The small hive beetle, Aethina tumida Murray (Coleoptera: Nitidulidae), and the ectoparasitic mite Varroa destructor Anderson & Trueman are honey bee parasites and both overwinter in host colonies. The efficiency of thermoregulation might thus be affected in infested host winter clusters, due to altered worker activity. Here, we show for the first time that parasites can alter honey bee thermoregulation. Moreover, the data suggest that only combined infestations with V. destructor and A. tumida result in higher thermal maxima in the winter clusters, whereas infestations with one parasite alone had no significant effect compared with the controls. Due to the ubiquitous mite V. destructor combined infestations with parasites or combined infections with pathogens are almost inevitable. Therefore, our data indicate that an altered thermoregulation due to multiple infestations might be another widespread factor contributing to winter losses of honey bee colonie

Historical Data Review of Dissolved Oxygen and Related Parameters for the Lavaca Bay TMDL Project

"This historical data review is part of the Lavaca Bay/Chocolate Bay (Segment 2453) Total Maximum Daily Load (TMDL) Project. The data generated will be used to identify areas within the segment for further investigation, assess the segment for Dissolved Oxygen (DO) exceedences, and support the development of a TMDL for DO. Segment 2453 was listed on the 305(b) list because DO concentrations are occasionally lower than the criterion established to assure optimum conditions for aquatic life in a 13.7-square mile area near the Alcoa Ship channel. “Aquatic life use” is a term used in Texas water resource management to characterize water bodies and specify water quality criteria for those bodies. The Texas Natural Resource Conservation Commission (TNRCC) has identified four aquatic life use categories: exceptional, high, intermediate, and limited. The TNRCC criteria for DO varies with the Aquatic life use designation of a water body (Table 1; Texas Natural Resource Conservation Commission, 2000). For Texas estuaries designated with exceptional aquatic life use, DO criteria are 24-hr mean < 5.0 mg 1⁻¹ and 24-hr minimum < 4.0 mg 1⁻¹. Lavaca Bay (segment 2453) is designated for exceptional aquatic life use. Estuaries designated for high aquatic use must meet less strenuous criteria of 24-hr mean < 4.0 mg 1⁻¹ and 24-hr minimum < 3.0 mg 1⁻¹. Dissolved oxygen is a parameter used to evaluate aquatic ecosystem health. Dissolved oxygen is a useful indicator because it is required for organism respiration and microbial sediment decomposition processes (Strobel and Heltshe 2000). In addition, low DO (i.e., hypoxia) can be caused by excess nutrient inputs into the aquatic system (e.g., sewage outfalls, non-point source pollution, etc.)"--Introduction.Texas Natural Resource Conservation Commission Contract No. 582-1-30479Marine Scienc

Promises and pitfalls of deep neural networks in neuroimaging-based psychiatric research

By promising more accurate diagnostics and individual treatment recommendations, deep neural networks and in particular convolutional neural networks have advanced to a powerful tool in medical imaging. Here, we first give an introduction into methodological key concepts and resulting methodological promises including representation and transfer learning, as well as modelling domain-specific priors. After reviewing recent applications within neuroimaging-based psychiatric research, such as the diagnosis of psychiatric diseases, delineation of disease subtypes, normative modeling, and the development of neuroimaging biomarkers, we discuss current challenges. This includes for example the difficulty of training models on small, heterogeneous and biased data sets, the lack of validity of clinical labels, algorithmic bias, and the influence of confounding variables

Real-time assessment of flash flood impacts at pan-European scale: the ReAFFINE method

The development of early warning systems (EWSs) is a key element for the effective mitigation of flash flood impacts. Emergency managers and other end-users increasingly recognise the benefit of tools that automatically translate the forecasted flash flood hazard (e.g. expressed in terms of peak discharge or return period) into the expected socio-economic impacts (e.g. the affected population). While previous studies aimed at forecasting flash flood impacts at local or regional scales, this paper presents a simple approach for estimating in real time the flash flood impacts at pan-European scale. The proposed method – named ReAFFINE – is designed to be integrated into an EWS for end-users operating over large spatial domains (e.g. across regions or countries). ReAFFINE uses the pan-European flash flood hazard estimates from the ERICHA system to retrieve the potentially flooded areas from the national flood maps (generated in the framework of the EU Floods Directive). By combining the potentially flooded areas with socio-economic exposure information, ReAFFINE estimates in real time the exposed population and critical infrastructures. For two catastrophic flash flood events affecting Europe in recent years, ReAFFINE has demonstrated the capability to identify impacts over large spatial scales. Also at sub-regional level, the method has mostly been able to locate the areas and municipalities where the most important impacts occurred. The results also show that the performance is sensitive to the quality of the rainfall estimates that drive the hazard estimation, and to the comprehensiveness of the employed flood maps.The EU Horizon 2020 project ANYWHERE (H2020-DRS-1-2015-700099) financed the initial period of this work. The study was finalised in the framework of the TAMIR project (UCPM-874435-TAMIR). We would like to express our gratitude to OPERA, WMO and the Spanish State Meteorological Agency (AEMET) for the provision of meteorological data, and the Spanish National Geographic Institute (IGN) and the German Federal Institute of Hydrology (BfG) for access to the national flood maps. Furthermore, we would like to thank OpenStreetMaps, Milan Kalas, and the Joint Research Centre for providing the pan-European exposure datasets, and the European Severe Weather Database (ESWD), the Bavarian Environment Agency (LfU), the Spanish Insurance Compensation Consortium (CCS), the Spanish Directorate-General for Civil Protection and Emergencies (DGPCE), and Jens de Bruijn (Vrije Universiteit Amsterdam) from the Global Flood Monitor for meticulously reporting the impacts of the analysed flood events.Peer ReviewedPostprint (published version