Finite-size scaling in the interfacial stiffness of rough elastic contacts

The total elastic stiffness of two contacting bodies with a microscopically rough interface has an interfacial contribution K that is entirely attributable to surface roughness. A quantitative understanding of K is important because it can dominate the total mechanical response and because it is proportional to the interfacial contributions to electrical and thermal conductivity in continuum theory. Numerical simulations of the dependence of K on the applied squeezing pressure p are presented for nominally flat elastic solids with a range of surface roughnesses. Over a wide range of p, K rises linearly with p. Sublinear power-law scaling is observed at small p, but the simulations reveal that this is a finite-size effect. We derive accurate, analytical expressions for the exponents and prefactors of this low-pressure scaling of K by extending the contact mechanics theory of Persson to systems of finite size. In agreement with our simulations, these expressions show that the onset of the low-pressure scaling regime moves to lower pressure as the system size increases.Comment: Supplementary material is available at arXiv:1210.4255, 5 pages, 3 figure

Wärmeübertragung durch überlagerte Strömungen an gestapelte Güter am Beispiel des Flachgeschirr-Brandes in Durchlauföfen

Der Wärmeübergang an gestapelte Güter spielt eine wesentliche Rolle bei der ökonomischen Auslegung von Thermoprozessanlagen. Gleichungen für die Wärmeübertragung an solch komplexe Geometrien sind aber nicht, bzw. nur in stark vereinfachter Form vorhanden. In der vorliegenden Arbeit wurde die Wärmeübertragung für die komplexe Geometrie "Tellerstapel" sowohl experimentell als auch mit Hilfe von Computersimulation bestimmt. Die Ergebnisse beider Methoden zeigen gute bis sehr gute Übereinstimmung. Des Weiteren wurde der Wärmeübergang durch Strahlung mit in die Simulation einbezogen und sein Verhältnis gegenüber dem konvektiven Wärmeübergang ermittelt. Für die Wärmeübergangsberechnung bei anderen Geometrien gestapelter Güter wurden mehrere Wege aufgezeigt und auf die zeit- und kostensparende Nutzung moderner Simulationsmethoden hingewiesen

Surface acoustic wave spectroscopy versus nanoindentation: Potentials and limits for coating characterization

Measuring mechanical film properties is essential for understanding and designing coating systems as well for controlling quality in coating manufacturing. Since more than two decades, two methods for determining Young’s modulus and other mechanical properties of thin films are widely used: The instrumented indentation technique (nanoindentation) and the laser-induced surface acoustic wave spectroscopy (LiSAWS). Due to their different physical principles, both methods address different fields of application but also complement each other. This presentation gives an overview for typical applications, strengths and limits for both methods from practical points of view like precision, requirements for sample material, preparation and test setup, additional results, standardization, and measuring time. Several examples for the application of both methods are discussed: • Hard protective coatings (deposited by PVD and thermal spraying) measured with both techniques • Films with less than 15 nm thickness • Effect of texture, microstructure and defects on measured propertie

Effects of Take-Over Requests and Cultural Background on Automation Trust in Highly Automated Driving

Appropriate automation trust is a prerequisite for safe, comfortable andefficient use of highly automated driving systems (HADS). Earlier researchindicates that a drivers’ nationality and Take-Over Requests (TOR) due toimperfect system reliability might affect trust, but this has never been investigatedin the context of highly automated driving. A driving simulator study (N = 80)showed that TORs only temporarily lowered trust in HADSs, and revealedsimilarities in trust formation between German and Chinese drivers. Trust wassignificantly higher after experiencing the system than before, both for German andChinese participants. However, Chinese drivers reported significantly higherautomation mistrust than German drivers. Self-report measures of automation trustwere not connected to behavioral measures. The results support a distinctionbetween automation trust and mistrust as separate constructs, short- and long-termeffects of TORs on automation trust, and cultural differences in automation trust

Efficient Forecasting for Hierarchical Time Series

Forecasting is used as the basis for business planning in many application areas such as energy, sales and traffic management. Time series data used in these areas is often hierarchically organized and thus, aggregated along the hierarchy levels based on their dimensional features. Calculating forecasts in these environments is very time consuming, due to ensuring forecasting consistency between hierarchy levels. To increase the forecasting efficiency for hierarchically organized time series, we introduce a novel forecasting approach that takes advantage of the hierarchical organization. There, we reuse the forecast models maintained on the lowest level of the hierarchy to almost instantly create already estimated forecast models on higher hierarchical levels. In addition, we define a hierarchical communication framework, increasing the communication flexibility and efficiency. Our experiments show significant runtime improvements for creating a forecast model at higher hierarchical levels, while still providing a very high accuracy

University Libraries and the Open Research Knowledge Graph

The transfer of knowledge has not changed fundamentally for many hundreds of years: It is usually document-based - formerly printed on paper as a classic essay and nowadays as PDF. With around 2.5 million new research contributions every year, researchers drown in a flood of pseudo-digitized PDF publications. As a result research is seriously weakened. In this article, we argue for representing scholarly contributions in a structured and semantic way as a knowledge graph. The advantage is that information represented in a knowledge graph is readable by machines and humans. As an example, we give an overview on the Open Research Knowledge Graph (ORKG), a service implementing this approach. For creating the knowledge graph representation, we rely on a mixture of manual (crowd/expert sourcing) and (semi-)automated techniques. Only with such a combination of human and machine intelligence, we can achieve the required quality of the representation to allow for novel exploration and assistance services for researchers. As a result, a scholarly knowledge graph such as the ORKG can be used to give a condensed overview on the state-of-the-art addressing a particular research quest, for example as a tabular comparison of contributions according to various characteristics of the approaches. Further possible intuitive access interfaces to such scholarly knowledge graphs include domain-specific (chart) visualizations or answering of natural language questions

Social responsibility in research and innovation practice and policy across global regions, institutional types, and fields:Interview data and qualitative content analysis outputs revealing the perspectives and experiences of professionals

The European Commission-funded RRING (Responsible Research and Innovation Networked Globally) Horizon 2020 project aimed to deliver activities that promoted a global understanding of Socially Responsible Research and Innovation (RRI). A necessary first step in this process was to understand how researchers (working across Global North and Global South contexts) implicitly understand and operationalise ideas relating to social responsibility within their day-to-day work. Here, we describe an empirical dataset that was gathered as part of the RRING project to investigate this topic. This Data Note explains the design and implementation of 113 structured qualitative interviews with a geographically diverse set of researchers (across 17 countries) focusing on their perspectives and experiences. Sample selection was aimed at maximising diversity. As well as spanning all five UNESCO world regions, these interview participants were drawn from a range of research fields (including energy; waste management; ICT/digital; bioeconomy) and institutional contexts (including research performing organisations; research funding organisations; industry and business; civil society organisations; policy bodies). This Data Note also indicates how and why a qualitative content analysis was implemented with this interview dataset, resulting in category counts available with the anonymised interview transcripts for public access.</p

Determining the value of preferred goods based on consumer demand in a home-cage based test for mice

From the preference of one good over another, the strength of the preference cannot automatically be inferred. While money is the common denominator to assess the value of goods in humans, it appears difficult at first glance to put a price tag on the decisions of laboratory animals. Here we used consumer demand tests to measure how much work female mice expend to obtain access to different liquids. The mice could each choose between two liquids, one of which was free. The amount of work required to access the other liquid, by contrast, increased daily. In this way, the value of the liquid can be determined from a mouse's microeconomic perspective. The unique feature is that our test was carried out in a home-cage based setup. The mice lived in a group but could individually access the test-cage, which was connected to the home-cage via a gate. Thereby the mice were able to perform their task undisturbed by group members and on a self-chosen schedule with minimal influence by the experimenter. Our results show that the maximum number of nosepokes depends on the liquids presented. Mice worked incredibly hard for access to water while a bitter-tasting solution was offered for free whereas they made less nosepokes for sweetened liquids while water was offered for free. The results demonstrate that it is possible to perform automated and home-cage based consumer demand tests in order to ask the mice not only what they like best but also how strong their preference is