University of Stuttgart

About: University of Stuttgart is a education organization based out in Stuttgart, Germany. It is known for research contribution in the topics: Laser & Finite element method. The organization has 27715 authors who have published 56370 publications receiving 1363382 citations. The organization is also known as: Universität Stuttgart.

Deep Learning Based Communication Over the Air

Abstract: End-to-end learning of communications systems is a fascinating novel concept that has so far only been validated by simulations for block-based transmissions. It allows learning of transmitter and receiver implementations as deep neural networks (NNs) that are optimized for an arbitrary differentiable end-to-end performance metric, e.g., block error rate (BLER). In this paper, we demonstrate that over-the-air transmissions are possible: We build, train, and run a complete communications system solely composed of NNs using unsynchronized off-the-shelf software-defined radios and open-source deep learning software libraries. We extend the existing ideas toward continuous data transmission, which eases their current restriction to short block lengths but also entails the issue of receiver synchronization. We overcome this problem by introducing a frame synchronization module based on another NN. A comparison of the BLER performance of the “learned” system with that of a practical baseline shows competitive performance close to $\text{1}$ dB, even without extensive hyperparameter tuning. We identify several practical challenges of training such a system over actual channels, in particular, the missing channel gradient, and propose a two-step learning procedure based on the idea of transfer learning that circumvents this issue.

Production Workflow: Concepts and Techniques

Abstract: 1. Introduction. Business Processes. Business Processes as Enterprise Resource. Virtual Enterprises. Processes and Workflows. Dimensions of Workflow. User Support. Categories of Workflows. Application Structure. Workflow and Objects. Application Operating System. Software Stack. Document/Image Processing. Groupware and Workflow. Different Views of Applications. Transactional Workflow. Advanced Usage. System Requirements. Relation to Other Technologies. 2. Business Engineering. Business Modeling. Business Logic. Enterprise Structure. Information Technology Infrastructure. Business Modeling Example. Business Process Reengineering. Process Discovery. Process Optimization. Process Analysis. Business Engineering and Workflow. Monitoring. 3. Workflow Management System Basics. Main Components. Types of Users. Buildtime. Metamodel Overview. Runtime. Audit Trail. Process Management. Authorization. Application Programming Interface. System Structure. Workflow Standards. 4. Metamodel. The Notion of a Metamodel. Process Data. Activities. Control Flow. Data Flow. Summary: PM-Graphs. Navigation. Summary: G-Instances. 5. Advanced Functions. Events. Dynamic Modification of Workflows. Advanced Join Conditions. Container Materialization. Object Staging. Context Management. Performance Spheres. Compile Spheres. 6. Workflows and Objects. Component-based Software Construction. Scripts in Object-Oriented Analysis and Design. The Object Request Broker. The OMG Workflow Management Facility. 7. Workflows and Transactions. Basic Transaction Concepts. Advanced Transaction Concepts. Streams. Atomic Spheres. Compensation Spheres. Phoenix Behavior. 8. Advanced Usage. Monitoring Dynamic Integrity Rules. Software Distribution. Security Management. Business-Process-Oriented Systems Management. 9. Application Topologies. Dependent Applications. Client/Server Structures. TP Monitors. Communication Paradigms. Message Monitors. Message Broker. Object Brokers. Distributed Applications. Web Applications. Workflow-based Applications. 10. Architecture and System Structure. Architectural Principles. System Structure. Servers. Client. Program Execution. System Group. Domains. System Tuning. Workload Management. Systems Management. Exploiting Parallel Databases. Server Implementation Aspects. Navigation. Message Queuing Usage. Process Compiler. 11. Development of Workflow-based Applications. Development Environment Blueprint. Component Generation. Testing. Animation. Debugging Activity Implementations. Application Database Design. Application Tuning. Optimization. A Travel Reservation Example. B List of Symbols. Bibliography. Index.

Impact of land use intensity on the species diversity of arbuscular mycorrhizal fungi in agroecosystems of Central Europe

Abstract: The impact of land use intensity on the diversity of arbuscular mycorrhizal fungi (AMF) was investigated at eight sites in the “three-country corner” of France, Germany, and Switzerland. Three sites were low-input, species-rich grasslands. Two sites represented low- to moderate-input farming with a 7-year crop rotation, and three sites represented high-input continuous maize monocropping. Representative soil samples were taken, and the AMF spores present were morphologically identified and counted. The same soil samples also served as inocula for “AMF trap cultures” with Plantago lanceolata, Trifolium pratense, and Lolium perenne. These trap cultures were established in pots in a greenhouse, and AMF root colonization and spore formation were monitored over 8 months. For the field samples, the numbers of AMF spores and species were highest in the grasslands, lower in the low- and moderate-input arable lands, and lowest in the lands with intensive continuous maize monocropping. Some AMF species occurred at all sites (“generalists”); most of them were prevalent in the intensively managed arable lands. Many other species, particularly those forming sporocarps, appeared to be specialists for grasslands. Only a few species were specialized on the arable lands with crop rotation, and only one species was restricted to the high-input maize sites. In the trap culture experiment, the rate of root colonization by AMF was highest with inocula from the permanent grasslands and lowest with those from the high-input monocropping sites. In contrast, AMF spore formation was slowest with the former inocula and fastest with the latter inocula. In conclusion, the increased land use intensity was correlated with a decrease in AMF species richness and with a preferential selection of species that colonized roots slowly but formed spores rapidly.

Mass balance of the Antarctic ice sheet from 1992 to 2017.

Abstract: The Antarctic Ice Sheet is an important indicator of climate change and driver of sea-level rise. Here we combine satellite observations of its changing volume, flow and gravitational attraction with modelling of its surface mass balance to show that it lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017, which corresponds to an increase in mean sea level of 7.6 ± 3.9 millimetres (errors are one standard deviation). Over this period, ocean-driven melting has caused rates of ice loss from West Antarctica to increase from 53 ± 29 billion to 159 ± 26 billion tonnes per year; ice-shelf collapse has increased the rate of ice loss from the Antarctic Peninsula from 7 ± 13 billion to 33 ± 16 billion tonnes per year. We find large variations in and among model estimates of surface mass balance and glacial isostatic adjustment for East Antarctica, with its average rate of mass gain over the period 1992–2017 (5 ± 46 billion tonnes per year) being the least certain.

A Rydberg quantum simulator

Abstract: A universal quantum simulator is a controlled quantum device that reproduces the dynamics of any other many-particle quantum system with short-range interactions. This dynamics can refer to both coherent Hamiltonian and dissipative open-system evolution. Here we propose that laser-excited Rydberg atoms in large-spacing optical or magnetic lattices provide an efficient implementation of a universal quantum simulator for spin models involving n-body interactions, including such of higher order. This would allow the simulation of Hamiltonians of exotic spin models involving n-particle constraints, such as the Kitaev toric code, colour code and lattice gauge theories with spin-liquid phases. In addition, our approach provides the ingredients for dissipative preparation of entangled states based on engineering n-particle reservoir couplings. The basic building blocks of our architecture are efficient and high-fidelity n-qubit entangling gates using auxiliary Rydberg atoms, including a possible dissipative time step through optical pumping. This enables mimicking the time evolution of the system by a sequence of fast, parallel and high-fidelity n-particle coherent and dissipative Rydberg gates. Building on recent experimental advances in controlling individual Rydberg atoms, theoretical work proposes a ‘Rydberg quantum simulator’. Such a system would be suitable for efficiently simulating other quantum systems with many-body interactions and strongly correlated ground states.