Numerical methods for the fatigue assessment of welded joints: influence of misalignment and geometric weld imperfections

The fatigue design life of welded joints in steel structures is increasingly assessed by using numerical models and methods, such as the structural (hot-spot) stress method and the effective notch stress method. When compared to the classical design approach using nominal stress S-N design curves, these methods offer the advantage of flexibility and a wider scope of application. However, a number of questions arise when these methods are used to assess geometrically "imperfect" welded joints, such as joints with plate misalignments or excessive weld convexity or concavity. In these cases, the classical S-N curves are known to cover imperfections up to the common tolerance classes for fatigue-prone welded joints (e.g. in accordance with ISO 5817 class B). For the numerical methods, differing and conflicting recommendations exist on how to account for the geometric imperfections in the welded joints, with little or no background to these recommendations available. In this paper, a study is presented in which two standard welded joints (butt welds between plates of equal and unequal thickness; T-joints with fillet welds) are analysed with the help of the structural (hot-spot) stress and the effective notch stress approach, considering various levels of geometric imperfection up to the tolerance limits, and the resulting fatigue life predictions are compared to test results from the literature and the nominal stress approach predictions. Since the nominal stress approach curves are based on reliable statistical data and desired survival probabilities for these known, standard cases, this methodology allows one to determine the correct application of the numerical methods to cases with geometric imperfections. This information may be used for a pertinent refinement of design recommendations for these methods, as well as for cases where these methods are applied to fitness-for-purpose assessments - e.g. because the nominal stress approach is not applicable

The influence of urban lawn mowing regimes on diversity of Heteroptera (Hemiptera)

In order to analyse the potential of an extensive mowing regime for influencing the biodiversity of insects on public urban grassland areas in a middle-sized town, we compared intensively mowed lawns (one mowing event per month) with meadows that were extensively mowed only twice a year. Over the entire field season, 335 true bug individuals of 49 species and 12 families were caught by using spoon nets and an insect aspirator. We established that the process of mowing on a regular monthly basis reduced heteropteran biodiversity about 50% per mowing event. Moreover, extensively mowed meadows showed significantly higher total species numbers and biodiversity indices. With respect to true bugs, lawns were characterised by the absence of typical meadow species that could be found on the extensively mowed study plots. Our research supports the initiative “Bunte Wiese (Colourful Meadow) – Species Diversity in Public Greenspaces” of the University of Tübingen, which is campaigning for the enhancement of species diversity in public urban greenland areas by reorganising the intensive mowing into a “twice a year”-programme.Die Häufigkeit der Mahd von Grünflächen hat einen großen Einfluss auf die Entwicklung von Pflanzen und Tieren. Insbesondere Insektenpopulationen können durch eine hohe Mahdfrequenz empfindlich geschädigt werden. In vorliegender Arbeit untersuchten wir daher die Auswirkung der Reduktion der Mahdfrequenz innerstädtischer Rasenflächen auf die Wanzenvielfalt. Die Umstellung von intensiver Rasenpflege zu extensiver Wiesenmahd ermöglichte es uns, während einer Vegetationsperiode 335 Wanzen aus 49 Arten und 12 Familien zu fangen. Der Vergleich mit weiterhin intensiv gepflegten Rasenflächen zeigte uns, dass die monatliche Mahd die Wanzenpopulation um etwa 50% pro Mahd reduziert. Extensiv gepflegte Stadtwiesen zeigten eine signifikant höhere Artenzahl und höhere Biodiversitätsindizes. In Bezug zur Wanzenzönose lassen sich intensiv gepflegte Rasenflächen durch die Abwesenheit von typischen Graslandwanzen charakterisieren. Unsere Ergebnisse unterstützen die Ziele und Argumente der Initiative „Bunte Wiese – Für mehr Artenvielfalt auf öffentlichem Grün” der Universität Tübingen, welche einen Beitrag zur Verminderung des weltweiten Insektensterbens leisten möchte, indem sie für eine weitreichende Extensivierung der Mahd eintritt und dadurch flächendeckend artenreiche Grünflächen schaffen möchte, welche Lebensraum für Pflanzen und Tiere bieten

Genotoxicity of Superparamagnetic Iron Oxide Nanoparticles in Granulosa Cells

Nanoparticles that are aimed at targeting cancer cells, but sparing healthy tissue provide an attractive platform of implementation for hyperthermia or as carriers of chemotherapeutics. According to the literature, diverse effects of nanoparticles relating to mammalian reproductive tissue are described. To address the impact of nanoparticles on cyto- and genotoxicity concerning the reproductive system, we examined the effect of superparamagnetic iron oxide nanoparticles (SPIONs) on granulosa cells, which are very important for ovarian function and female fertility. Human granulosa cells (HLG-5) were treated with SPIONs, either coated with lauric acid (SEONLA) only, or additionally with a protein corona of bovine serum albumin (BSA;SEONLA-BSA),or with dextran (SEONDEX). Both micronuclei testing and the detection of H2A.X revealed no genotoxic effects of SEONLA-BSA, SEONDEX or SEONLA. Thus, it was demonstrated that different coatings of SPIONs improve biocompatibility, especially in terms of genotoxicity towards cells of the reproductive system

Implementing a blockchain from scratch: why, how, and what we learned

Abstract Blockchains are proposed for many application domains apart from financial transactions. While there are generic blockchains that can be molded for specific use cases, they often lack a lightweight and easy-to-customize implementation. In this paper, we introduce the core concepts of blockchain technology and investigate a real-world use case from the energy domain, where customers trade portions of their photovoltaic power plant via a blockchain. This does not only involve blockchain technology, but also requires user interaction. Therefore, a fully custom, private, and permissioned blockchain is implemented from scratch. We evaluate and motivate the need for blockchain technology within this use case, as well as the desired properties of the system. We then describe the implementation and the insights from our implementation in detail, serving as a guide for others and to show potential opportunities and pitfalls when implementing a blockchain from scratch

Urban Nature: Perception and Acceptance of Alternative Green Space Management and the Change of Awareness after Provision of Environmental Information. A Chance for Biodiversity Protection

Measurable ecological data, e.g., species diversity, provide inadequate information for achieving the comprehensive protection of biodiversity, because human acceptance attitudes can be important factors in undermining nature protection schemes. We have analysed an ecologically driven urban management system presented to urban habitants. A photograph-based survey answered by 424 participants was used to evaluate their impressions of natural meadows. The positive effect of provided information tables was demonstrated by pre- and post-test designs. Attitudes towards urban nature protection showed a statistical preference for green-area management systems optimising insect protection compared with more regularly mowed meadows and lawns. Thus, the perceptions of people should be considered in processes of biodiversity protection. Our results correlate with personal attitude and education, support the aims of extensive green-space management and should encourage urban planners to integrate biodiversity protection zones into urban planning

Perception of Urban Green Areas Associated with Sociodemographic Affiliation, Structural Elements, and Acceptance Stripes

The extensification (opposite of intensification) of urban public green spaces offers great potential for conservation. One major issue for the long-term success of such a measure is, however, its acceptance by the urban population. This contribution presents the results of an image-based online questionnaire that we set to elucidate the role of sociodemographic affiliations regarding the perception of urban green areas. We also asked whether acceptability can be increased by the presence of additional structural elements (sculptures, benches) and “acceptance stripes”, i.e., stripes regularly mowed only at the margins of a natural green space. Regarding structural elements, 40- to 60-year-olds consistently rejected intensely maintained lawns and perceived a lawn as positive only in combination with a sculpture. A regularly mowed acceptance stripe resulted in a positive perception of natural meadows by people with an affinity for city life, classified based on their actual place of residence and/or their social dimension including aspects such as sense of place, familiarity, profession, and interests. Thus, decision-making processes of policy makers must be evaluated together with the urban population and should be assessed multidimensionally, i.e., by considering various criteria (e.g., ecological, social, and aesthetic aspects) in order to meet the requirements of residents and achieve an increase in biodiversity

An industry-level blu-ray watermarking framework

In this paper, we present our H.264 Blu-ray watermarking framework which operates at bit stream level and preserves the length of the underlying bit stream. Apart from a description of our watermark embedding and detection (and synchronisation) approaches, we discuss the embedding capacity for different exemplary Blu-ray disks based on their bit stream characteristics as well as the robustness of our watermark to H.264 transcoding and resizing. Furthermore, we assess the parallelizability of our embedding approach and the impact of different hard drive configurations on the overall embedding speed, showing that low access times are as relevant as high transfer rates when maximum speedup through parallelization is desired. Lastly, this paper provides a discussion on a variety of design choices and practical issues which arise when designing an industry-level watermarking framework

A Generic Model for Universal Data Storage and Conversion and Its Web based Prototypical Implementation

ABSTRACT This paper presents a prototypical, Web based data conversion framework and its underlying data representation principles which allow conversions from and to any data format. Therefore, a data model is proposed which allows storing values of arbitrary types, including inter-data dependencies and meta information. Furthermore, an Extensible Markup Language (XML) based model to describe data formats is provided which allows specifying programs to convert data represented in existing formats both from and to the proposed data model. It will be shown that these programs are Turing complete, thus allowing the same arbitrarily complex conversions which are possible with Extensible Stylesheet Language Transformations (XSLT) or the C programming language. Finally, the components of a prototypical Web based implementation in form of a validator, a data converter and a data generator are described. In combination with a data editor, parts of this prototypical implementation are already employed in several use cases in the industry and other research projects to transform data between different formats. INTRODUCTION Whenever huge quantities of information from industrial applications need to be stored, transformation and manipulation of data is a complex issue. Vast amount of data combined with proprietary data formats, which are generated from different data sources, pose a great challenge for data handling. To address this issue, we present a fully integrated solution which enables storage and transformation of arbitrary data formats. Our approach is based on two essential models: a generic data model and an XML model. The generic data model allows storage of arbitrary data formats, including meta information and interdependencies. The XML model specifies data formats and serves as transformation language from and to the original data representations. In addition, a universal data converter and a generator are implemented in a prototype framework