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20:20 Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB) Englisch 2018

Conference recordings complement scholarly research communication in traditional conference proceedings

Traditionally, research results presented at scientific conferences are published in conference proceedings. Additionally, an increasing number of conferences are recorded and the videos are subsequently published. In most cases these videos are published by the organisers on commercial platforms or directly on the conference website. Therefore, a systematic search for conference recordings is difficult. Moreover, the videos are often lost after a short time e.g. because the URL changes or external links lead to nowhere. Usually, conference websites are not maintained on a long-term basis and commercial platforms may remove videos or change the conditions for access for a variety of reasons. Finally, to ensure an unproblematic re-use of the material questions of licencing, technical quality and formats have to be solved in advance. In order to prevent the loss of conference recordings the German National Library of Science and Technology (TIB) has developed the AV-Portal. The AV-Portal provides the ideal infrastructure to host, find and reuse scientific videos. It's a single access point for videos from different conferences and years. All videos are assigned a Digital Object Identifier (DOI). These persistent identifiers allow for reliable referencing both as stable online links and as correct citations in scholarly work. In this talk we describe how sharing scientific results via audio-visual media has become an important part of scientific communication and how conference recordings may complement the classical conference proceedings and add new value to the presented research. By discussing the whole process from pre-conference organisation to publishing and archiving the recordings we show pitfalls, best practices and opportunities of recordings for both conference organisers and participants.
  • Erscheinungsjahr: 2018
  • Herausgeber: Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB)
  • Sprache: Englisch
20:10 Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB) Englisch 2018

A benchmark study for CFD solvers: simulation of air flow in livestock husbandry

In this work we present the results of a joint effort of three Leibniz Institutes (ATP, TROPOS and WIAS) leading to the validation of numerical methods and software for fluid simulations. The benchmark problem is motivated by the application in livestock husbandry, in which the understanding flow characteristics is of extreme importance in order to guarantee good quality fresh air and being environmentally sparing.In this field, CFD represents a valuable tool that enable simulation of flow patterns in different configurations. In order to assess the performance of different CFD approaches (including different solver, flow models and numerical methods) three open source models are compared: ASAM (developed at TROPOS), OpenFOAM and ParMooN (developed at WIAS). The results are compared with measurements obtained by wind tunnel experiments.
  • Erscheinungsjahr: 2018
  • Herausgeber: Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB)
  • Sprache: Englisch
28:04 Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB) Englisch 2018

Analyzing paradigmatic language change by visual correlation

Paradigmatic language change occurs, when paradigmatically related words with similar usage rise or fall together. Such change is the rule rather than an exception. Words rarely increase or decrease in isolation but together with similar words. In the short term, this is usually due to thematic change, but in the longer term, also grammatical preferences change. We present an approach to visually explore paradigmatic change by reducing the dimensionality of and correlating the two main factors involved: Frequency change and distributional semantics of words. Frequency change is reduced to one dimension by means of fitting the logistic growth curves to the observed word frequencies in fixed intervals (e.g. year or decade). Semantics of words reduced to two dimensions such that words with similar usage contexts are positioned closely together. This is accomplished by reducing the very high dimensional representation of word usage context in two steps. Neural network based word embeddings and t-Distributed Stochastic Neighbour Embedding.
  • Erscheinungsjahr: 2018
  • Herausgeber: Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB)
  • Sprache: Englisch
18:46 Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB) Englisch 2018

Research data and mathematical modeling

Today, mathematical modeling is an important tool in scientific research. In mathematics, publications are containers for mathematical research data containing models and mathematical objects, theories, theorems, proofs, methods, algorithms, and applications. However, it is a nontrivial task to extract detailed information about models and other research data from publications. Especially, the information about mathematical models is given in different form, e.g., by names or in “natural mathematical language” (a combination of text and mathematical formulae), and is often incomplete. Moreover, different communities use different terminologies and notations for the same models. These deficits make it difficult to find and reuse existing models and lead to repeated reinventing the wheel. This results in an project idea to analyze and collect existing information about mathematical models in publications and to develop concepts for a semantic presentation of them. In the talk, the presentation of research data in mathematical publications will be analyzed and first ideas for a special model database are suggested.
  • Erscheinungsjahr: 2018
  • Herausgeber: Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB)
  • Sprache: Englisch
22:28 Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB) Englisch 2018

Software information and the swMATH service

Scientific software is an indensible tool for the automatization and control of complex problems. But what is software? Software is a entirety of different kinds of objects which is developing dynamically and cannot be reduced to software code. Moreover, software plays a special role: Software is in the middle between models and simulations. The distributed development of software and the access to the software have led to new concepts and tools for maintaining software and software information. The swMATH service is a portal for mathematical software. It provides landing pages for each software entry. These landing pages contain general information about the software products and links to a lot of resources which describe or use the software, e.g., websites of the software, repositories, Internet archives, and publications citing a software. The integration and analysis of different resources allows a nearly complete overview about the Web information of a software. In the talk, new features and future extensions of the swMATH service are presented.
  • Erscheinungsjahr: 2018
  • Herausgeber: Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB)
  • Sprache: Englisch
40:47 Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB) Englisch 2018

Key Note Lecture: Why is the desert not flat? The interesting physics of windblown sand.

Windblown sand creates a distinct hierarchy of mobile landforms on Earth on some celestial bodies, ranging from tapestries of meticulously carved ripples to vast fields of shifting dunes. They are often perceived as aesthetically appealing, yet economically and ecologically threatening. But how do they form, and what determines their characteristic shapes, sizes, and migration dynamics? I will sketch three crucial physical mechanisms that govern this whole phenomenology: spontaneous turbulent symmetry breaking, broken scale invariance due to an emergent mesoscale, and aeolian sand sorting. Together they give rise to the notion of a forbidden wavelength gap between ripples and dunes and explain why it can (only) be inhabited by a peculiar bedform known as megaripples, which might actually be better characterized as mini-dunes. K. Kroy, G. Sauermann, H. J. Herrmann, Minimal model for sand dunes, Physical Review Letters 88 (2002) 054301. M. Lämmel, K. Kroy, Analytical mesoscale modeling of aeolian sand transport, Physical Review E 96 (2017) 052906. M. Lämmel, A. Meiwald, H. Yizhaq, H. Tsoar, I. Katra, and K. Kroy, Aeolian sand sorting and megaripple formation, Nature Physics, to appear.
  • Erscheinungsjahr: 2018
  • Herausgeber: Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB)
  • Sprache: Englisch
21:32 Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB) Englisch 2018

Modelling turbulent fluid-, thermo-, and droplet dynamics in the Leipzig Aerosol Cloud Interaction Simulator (LACIS-T)

The turbulent Leipzig Aerosol Cloud Interaction Simulator (LACIS-T) is a Göttingen-type moist-air wind tunnel designed for investigating interactions between turbulence and cloud microphysics under reproducible and well defined thermo- and fluid dynamic conditions. To draw reliable conclusions from measurements at the wind tunnel it is necessary to have precise knowledge about the flow field and turbulent fluctuations of velocity, temperature, and water vapour concentration. For this reason, the flow inside the measurement section of LACIS-T is simulated with OpenFOAM, employing a Large Eddy Simulation model for turbulence. Different boundary conditions for water vapour concentration and temperature are considered and the results are compared to measurements. Furthermore, particles are tracked through the domain using a Lagrangian approach. Thereto, a suitable growth model is implemented to calculate particle/droplet growth due to the condensation of water vapour from the gas phase. Joint work with D. Niedermeier, J. Voigtländer, and F. Stratmann.
  • Erscheinungsjahr: 2018
  • Herausgeber: Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB)
  • Sprache: Englisch
24:16 Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB) Englisch 2018

Application of a dynamic turbulence parametrization in a circulation model

Preliminary results from the application of our recently developed extension of the Dynamic Smagorinsky model (DSM) are presented. The DSM serves as a parameterization for subgrid-scale momentum diffusion in a general circulation model (GCM) that allows for stable simulations even without a hyperdiffusion. Due to gravity, the horizontal and vertical scales have to be treated differently. Our extension includes a test filter for the Smagorinsky parameter that is separated from the resolution scale, and a dynamic approach for the vertical diffusion based on the ideas of stratified turbulence. The aim of our investigations is to extend our model into the MLT for a study of GW spectra with respect to the scaling ratio of stratified macro-turbulence. Therefore, we show the performance of the DSM up to the lower stratosphere and discuss the implications from the scale-invariance criterion for LES parameterizations on the approach for dynamic vertical diffusion.
  • Erscheinungsjahr: 2018
  • Herausgeber: Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB)
  • Sprache: Englisch
22:04 Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB) Englisch 2018

Numerical simulation of large atmospheric multiphase mechanisms and detailed combustion kinetics

A simulation tool for the numerical solution of large kinetic systems with special emphasis on examples from atmospheric chemistry and combustion is presented. The chemical mechanism has to be provided in readable ASCII format, whereas the program is able to read the TROPOS syntax for chemical systems and also the widely used ChemKin format. From this, a system of ordinary differential equations is generated internally and solved numerically by Rosenbrock-type methods. Efficiency is obtained by carefully exploiting the sparsity structures of the Jacobian. Additionally, another approach is implemented, where the direct evaluation of the Jacobian is no longer required. The effects of both strategies are investigated by simulating detailed atmospheric multiphase mechanisms and gas-phase combustion mechanisms.
  • Erscheinungsjahr: 2018
  • Herausgeber: Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB)
  • Sprache: Englisch
26:17 Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB) Englisch 2018

Czochralski Growth of Ge Computed by Using the Finite Element Tool Elmer

The Czochralski method is widely used for growing single crystals as e.g. silicon crystals. Typically, the thermal field and related ones such as thermal stress is computed for certain stages of the growth. Here we present the successive computations starting from inital state up to nearly the end by combining a perl script and the finite element solver Elmer. The shape of the crystal is given by input and can be taken either from experimental result or by own definition. The numerical computed interface is compared with the one observed by LPS at the crystal grown.
  • Erscheinungsjahr: 2018
  • Herausgeber: Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB)
  • Sprache: Englisch
33:36 Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB) Englisch 2018

Model pathway diagrams for the representation of mathematical models

Mathematical modeling and simulation (MMS) has now been established as an essential part of the scientific work in many disciplines. It is common to categorize the involved numerical data and to some extent the corresponding scientific software as research data. But both have their origin in mathematical models, therefore any holistic approach to research data in MMS should cover all three aspects: data, software, and models. However, finding an appropriate representation for models is far less obvious than for numerical data and software. The current practice of representing models is a mixture of mathematical formulae and natural language in scientific publications. This (rigorous, but) informal approach creates ambiguity, potential incompleteness of the presentation, less reproducibility and often "re-invention of the wheel". We present a concept for a machine-actionable as well as human-understandable of mathematical models based on Model Pathway Diagrams (MPD). MPDs specify the physical quantities that are described in the model as well as the relations between them (laws, constitutive equations) and informal documentation about them. MPDs provide a visual tool for understanding the structural properties of models as well as algorithms for numerical simulations. For a formalized representation of mathematical models and their underlying physics, we use the OMDoc/MMT, a special machine-readable description language for mathematical documents, that allows specifying the mathematical vocabulary of models, i.e. the concepts, their properties, and relations. We illustrate our approach by application to the van Roosbroeck system describing the carrier transport in semiconductors by drift and diffusion. We introduce an approach for the block-based composition of models from simpler components.
  • Erscheinungsjahr: 2018
  • Herausgeber: Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB)
  • Sprache: Englisch
34:11 Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB) Englisch 2018

Key Note Lecture: Challenges of atmospheric data assimilation

The initial state for atmospheric numerical models is produced by combining available observational data with a short range model simulation using a data assimilation algorithm. This gives us an initial state from which we can run a deterministic model to produce predictions of the future. The main goal of data assimilation is to produce the best analysis (best initial condition) for the numerical model; that is, the estimate that gives the best prediction for the time scales that we are focusing on. This is a challenging problem since high-resolution numerical models of the atmosphere in use today resolve highly nonlinear dynamics and physics, making them in short runs very sensitive to proper initial and boundary conditions. In this talk, we present the mechanisms of the data assimilation algorithms.. We focus on the ensemble Kalman filter algorithm to estimate the atmospheric state as well as its necessary modifications for our application. Most of the current algorithms used in practice for combining data and previous model forecasts (prior estimates) use Gaussian error assumptions. These assumptions are not appropriate for nonlinear dynamics, since only in the case of linear dynamics will Gaussian errors remain Gaussian in time, not in case of estimating variables that need to be positive or in certain ranges as, for example, rain. Consequently, data assimilation for numerical weather prediction models that resolve many scales of motion and for observations of higher temporal/spatial density/resolution requires re-evaluating and improving the methodology that is currently inherited from less nonlinear applications. We argue that relaxing underlying assumptions of the data assimilation algorithms might be possible by improving the link between the data assimilation and the model. For example, the stronger connection can be established by constraining the analysis with imposing conservation laws and other physical constraints. Applications are illustrated on the convective scale data assimilation example.
  • Erscheinungsjahr: 2018
  • Herausgeber: Weierstraß-Institut für Angewandte Analysis und Stochastik (WIAS), Technische Informationsbibliothek (TIB)
  • Sprache: Englisch
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