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Institution

Technische Universität Darmstadt

EducationDarmstadt, Germany
About: Technische Universität Darmstadt is a education organization based out in Darmstadt, Germany. It is known for research contribution in the topics: Neutron & Finite element method. The organization has 17316 authors who have published 40619 publications receiving 937916 citations. The organization is also known as: Darmstadt University of Technology & University of Darmstadt.


Papers
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Journal ArticleDOI
TL;DR: The microwave experiment has been realized to measure the phase difference of the oscillating electric field at two points inside the cavity and it is concluded that the state excited at the singularity has a definitive chirality.
Abstract: A microwave experiment has been realized to measure the phase difference of the oscillating electric field at two points inside the cavity. The technique has been applied to a dissipative resonator which exhibits a singularity-called exceptional point-in its eigenvalue and eigenvector spectrum. At the singularity, two modes coalesce with a phase difference of pi/2. We conclude that the state excited at the singularity has a definitive chirality.

195 citations

Journal ArticleDOI
TL;DR: A novel case study of a realistic distributed component-based system is presented, showing how queueing Petri net models can be exploited as a powerful performance prediction tool in the software engineering process.
Abstract: Performance models are used increasingly throughout the phases of the software engineering lifecycle of distributed component-based systems However, as systems grow in size and complexity, building models that accurately capture the different aspects of their behavior becomes a more and more challenging task In this paper, we present a novel case study of a realistic distributed component-based system, showing how queueing Petri net models can be exploited as a powerful performance prediction tool in the software engineering process A detailed system model is built in a step-by-step fashion, validated, and then used to evaluate the system performance and scalability Along with the case study, a practical performance modeling methodology is presented which helps to construct models that accurately reflect the system performance and scalability characteristics Taking advantage of the modeling power and expressiveness of queueing Petri nets, our approach makes it possible to model the system at a higher degree of accuracy, providing a number of important benefits

195 citations

Proceedings ArticleDOI
24 Jul 2016
TL;DR: Manifold Gaussian Processes is a novel supervised method that jointly learns a transformation of the data into a feature space and a GP regression from the feature space to observed space, which allows to learn data representations, which are useful for the overall regression task.
Abstract: Off-the-shelf Gaussian Process (GP) covariance functions encode smoothness assumptions on the structure of the function to be modeled. To model complex and non-differentiable functions, these smoothness assumptions are often too restrictive. One way to alleviate this limitation is to find a different representation of the data by introducing a feature space. This feature space is often learned in an unsupervised way, which might lead to data representations that are not useful for the overall regression task. In this paper, we propose Manifold Gaussian Processes, a novel supervised method that jointly learns a transformation of the data into a feature space and a GP regression from the feature space to observed space. The Manifold GP is a full GP and allows to learn data representations, which are useful for the overall regression task. As a proof-of-concept, we evaluate our approach on complex non-smooth functions where standard GPs perform poorly, such as step functions and robotics tasks with contacts.

195 citations

Journal ArticleDOI
TL;DR: It is concluded that L. terrestris burrow walls are stable microhabitats which sustain a large and active microbial community and are likely to play an important role in the soil system by regulating microbial-mediated chemical processes.
Abstract: Chemical characteristics and microbial activity were studied in burrow walls of the anecic earthworm species Lumbricus terrestris and in control soil of a lime ( Tilia cordata ), oak ( Quercus robur ) and beech ( Fagus sylvatica ) forest. Samples were taken in June and October at distances of 0–4 (drilosphere), 8–12 and 50–60 (control soil) mm from earthworm burrows. The following variables were measured: organic C, total N, moisture, pH, basal respiration, microbial biomass (SIR method), fungal and bacterial volume (epifluorescence microscopy) and nutrient (C, N and P) limitation of microbial growth. Organic C and total N contents increased in the burrow walls by factors of 1.8–3.5 and 1.3–2.2, respectively, compared to the control soil. The moisture content and pH (up to 1.2 units) was higher. Basal respiration, microbial biomass and bacterial volume in the drilosphere exceeded those in control soil significantly by factors of 3.7–9.1, 2.3–4.7 and 2.1–5.4, respectively. Changes in fungal volume with vicinity to burrows differed between forest sites. Fungal volume was increased significantly by factors of 1.9–3.4 in the earthworm burrow walls in the oak and beech forest, but was similar to that in control soil in the lime forest. Microbial growth in the control soil was limited by N in the oak forest and by N and P in the lime and beech forest. The nutrient status of the microflora changed little in vicinity to burrows. However, microbial N and P demand in earthworm burrow walls exceeded that in soil. The specific respiration ( q O 2 ) was increased and the growth response to nutrient additions was faster in the burrow walls suggesting that the microbial community in the burrow walls contains a larger fraction of metabolically-active microorganisms, adapted to continuous resource additions by earthworm faeces and mucus. Enrichment in organic matter, but also other mechanisms, particularly the activity of microbivorous soil animals, are presumably responsible for the formation of a specific microbial community in earthworm burrow walls. It is concluded that L. terrestris burrow walls are stable microhabitats which sustain a large and active microbial community and are likely to play an important role in the soil system by regulating microbial-mediated chemical processes.

195 citations

Journal ArticleDOI
TL;DR: It is concluded that inhibiting effects between Collembola and earthworms resulted from the use of a common resource, litter material rich in nitrogen.
Abstract: Effects of Collembola (Heteromurus nitidus and Onychiurus scotarius) and earthworms (Aporrectodea caliginosa and Octolasion tyrtaeum) on the growth of two plant species from different functional groups (Poa annua and Trifolium repens), and on the development of aphids (Myzus persicae) were investigated in a laboratory experiment lasting 20 weeks. Using soil from a fallow site which had been set aside for about 15 years, we expected that nitrogen would be of limited supply to plants and hypothesized that the soil animals studied, particularly earthworms, would increase nutrient availability to plants and thereby also modify aphid reproduction and development. Plant growth was modified strongly by the presence of soil animals. Earthworms caused a more than twofold increase in shoot and root mass of P. annua but increased that of T. repens by only 18% and 6%, respectively. However, earthworms neither affected plant shoot/root ratio nor the nitrogen concentration in plant tissue. In contrast, the presence of Collembola caused a reduction in plant biomass particularly that of P. annua roots, but plant tissue nitrogen concentration was increased, although only slightly. Aphid reproduction on T. repens was lowered in the presence of Collembola on average by 45% but on P. annua increased by a factor of about 3. It is concluded that Collembola decrease aphid reproduction on more palatable host plants like T. repens but increase that on less palatable ones like P. annua. Earthworm presence also affected aphid reproduction but the effect was less consistent than that of Collembola. In the presence of earthworms, aphid reproduction was in one experimental period increased by some 70%. Earthworms also modified the numbers of Collembola and their vertical distribution in experimental chambers. Exploitation of deeper soil layers by H. nitidus was increased but, generally, O. scotarius numbers were reduced whereas those of H. nitidus increased in earthworm treatments. The presence of Collembola also influenced earthworm body mass during the experiment. In general it declined, but in the presence of Collembola loss of body mass of A. caliginosa was more pronounced. We conclude that inhibiting effects between Collembola and earthworms resulted from the use of a common resource, litter material rich in nitrogen. This is supported by the higher C/N ratio of the litter material in the presence of earthworms and Collembola by the end of the experiment. Effects of soil invertebrates like Collembola and earthworms on plant performance and aphid development are assumed to be modified by complex direct and indirect interactions among soil animal groups.

195 citations


Authors

Showing all 17627 results

NameH-indexPapersCitations
Yang Gao1682047146301
Herbert A. Simon157745194597
Stephen Boyd138822151205
Jun Chen136185677368
Harold A. Mooney135450100404
Bernt Schiele13056870032
Sascha Mehlhase12685870601
Yuri S. Kivshar126184579415
Michael Wagner12435154251
Wolf Singer12458072591
Tasawar Hayat116236484041
Edouard Boos11675764488
Martin Knapp106106748518
T. Kuhl10176140812
Peter Braun-Munzinger10052734108
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
2023135
2022624
20212,462
20202,585
20192,609
20182,493