System Description: E 1.8

Abstract. E is a theorem prover for full first-order logic with equality. It reduces first-order problems to clause normal form and employs a saturation algorithm based on the equational superposition calculus. E is built on shared terms with cached rewriting, and employs several innovations for efficient clause indexing. Major strengths of the system are automatic problem analysis and highly flexible search heuristics. The prover can provide verifiable proof objects and answer substitutions with very little overhead. E performs well, solving more than 69 % of TPTP-5.4.0 FOF and CNF problems in automatic mode.

A consistent boundary method for the material point method - using imge particles to reduce boundary artefacts

The material point method (MPM) is a continuum-based numerical method hich discretises the object as material points. It is particulary ell suited for and has shon great success in the community for large deformations. Even though it has been idely adopted, ther are still fundamental questions to be addressed. In MPM the material properties are carried on the material points and the dynamics is calculated on an overlaid grid. Afterwards the material points are integrated according to are applied on the grid values, such as setting the grid momentum to zero for grid nodes inside a fixed wall. These disort the stress multiple grid lengths into the object. Inthis papr e propose a novel consistent boundary method to reduce these artefacts. The method is based on image particles, an approach originally developed for electrotatic problems. This concept allos a consistent formulation for the momentum field on both the grid and particles. We demonstrate a way of optimization that makes the explicit construction of mirror particles unnecessary. The explicit boundary method and image particle method are then compared using numerical examples featuring stress induced by simple shear and body forces. These numerical examples sho a significant reduction of boundary artefacts using the image particle method

Intraoperative Image Guidance in Neurosurgery: Development, Current Indications, and Future Trends

Introduction. As minimally invasive surgery becomes the standard of care in neurosurgery, it is imperative that surgeons become skilled in the use of image-guided techniques. The development of image-guided neurosurgery represents a substantial improvement in the microsurgical treatment of tumors, vascular malformations, and other intracranial lesions. Objective. There have been numerous advances in neurosurgery which have aided the neurosurgeon to achieve accurate removal of pathological tissue with minimal disruption of surrounding healthy neuronal matter including the development of microsurgical, endoscopic, and endovascular techniques. Neuronavigation systems and intraoperative imaging should improve success in cranial neurosurgery. Additional functional imaging modalities such as PET, SPECT, DTI (for fiber tracking), and fMRI can now be used in order to reduce neurological deficits resulting from surgery; however the positive long-term effect remains questionable for many indications. Method. PubMed database search using the search term “image guided neurosurgery.” More than 1400 articles were published during the last 25 years. The abstracts were scanned for prospective comparative trials. Results and Conclusion. 14 comparative trials are published. To date significant data amount show advantages in intraoperative accuracy influencing the perioperative morbidity and long-term outcome only for cerebral glioma surgery

Experimentelle und numerische Untersuchung von Gas/Liquid-Phasengrenzflächen als Referenzwert für die hydrostatische Füllstandsmessung in Siedewasserreaktoren

Die Dissertation bietet eine umfassende Analyse des quasi-stationären und dynamischen Verhaltens des Bezugspegels in den Nullkammerpegelgefäßen hydrostatischer Füllstandsmesssysteme von Siedewasserreaktoren. Die bislang rein phänomenologisch beschriebenen Übergangsprozesse im Pegelgefäß werden experimentell untersucht und in ihrer Wirkung auf das Messsystem bewertet. Da der Bezugsfüllstand und die Temperaturpulsationen sicherheitsrelevante Messgrößen sind, wird ein Beitrag zur Reaktorsicherheit geleistet. Die neuartigen, nichtinvasiven Verfahren zur Messung der Phasenverteilung im Pegelgefäß liefern realistische, unverfälschte Messdaten. Die Validierung von Simulationscodes und die sicherheitstechnische Bewertung von Siedewasserreaktoren werden dadurch verbessert. Das im CFD-Code Ansys CFX 14 entwickelte und experimentell validierte Modell bietet eine wichtige Grundlage für die numerische Simulation des Füllstandsmesssystems in Ergänzung zu Experimenten und zur Einbindung in Systemsimulationen

Experimental and numerical studies on the water balance of the Upper Mega Aquifer system, Arabian Peninsula

Besides a few perennial rivers, like the Euphrates, surface water resources are scarce and often not reliable in its temporal availability on the Arabian Peninsula. Consequently, the region relies on its mainly fossil groundwater reserves, which are predominantly stored in the sedimentary formations of the Arabian Platform. One of its major groundwater reservoirs is the Upper Mega Aquifer (UMA) system. The present thesis comprises three major studies on this aquifer system. The first one deals with a specific type of groundwater recharge: the accumulation of surface water and its discharge into karst features like open shafts and sinkholes. In order to quantify the amount of recharge, a combined approach of time-lapse camera monitoring and water balance modelling was applied. Finally, an average groundwater recharge rate of about 5 mm a-1 could be estimated for the As Sulb plateau, which constitutes an outcrop area of the Umm Er Radhuma karst aquifer. Moreover, this study discusses the non-linearity of recharge processes in arid environments. The second study deals with the groundwater evaporation from salt pans. During this study, different methods are used to provide a comprehensive picture of this process. These methods include satellite image analysis for the mapping of salt pan areas, isotopic investigations in order to distinguish between groundwater and seawater dominated salt pans, and a column experiment for the quantification of evaporation rates. A combination of these methods suggests a total annual groundwater loss of 1.3 km3 for the UMA system caused by the evaporation from salt pans. The third study encompasses the set-up and the calibration of a numerical groundwater flow model. In the course of this study, the phenomenon of fossil groundwater gradients is discussed and a novel calibration scheme is introduced. The final part of this thesis applies the model and three different development scenarios for groundwater abstraction are simulated and discussed

Social video: A collaborative video annotation environment to support E-learning

Our social video system allows users to enrich video by additional information like external websites, hypertext, images, other videos, or communication channels. Users are able to annotate whole videos, scenes, and objects in the video. We do not focus on a single user accessing the system but on multiple users watching the video and accessing the annotations others have created. Our web-based prototype differs from classical hypervideo systems because it allows annotation (authoring) and navigation in videos by focusing on collaboration and communication between the users. The prototype is integrated into the online social network Facebook and was evaluated with more than 300 users. The evaluation analyzes the usage of the system with a learning scenario in mind and indicates a learning success of users

Three dimensional large scale aerodynamic shape optimization based on shape calculus

Large scale three dimensional aerodynamic shape optimization based on the compressible Euler equations is considered. Shape calculus is used to derive an exact surface formulation of the gradients, enabling the computation of shape gradient information for each surface mesh node without having to calculate further mesh sensitivities. Special attention is paid to the applicability to large scale three dimensional problems like the optimization of an Onera M6 wing or a complete blended wing-body aircraft. The actual optimization is conducted in a one-shot fashion where the tangential Laplace-operator is used as a Hessian approximation, thereby also preserving the regularity of the shape

Phase diagram of three-leg ladders at strong coupling along the rungs

A phase diagram of the t-J three-leg ladder as a function of hole dopping is derived in the limit where the coupling parameters along the rungs, $t_{\perp}$ and $J_{\perp}$, are taken to be much larger than those along the legs, $t_{||}$ and $J_{||}$ At large exchange coupling along the rungs, $J_{\perp}/t_{\perp}> 3 / \sqrt{2}$, there is a transition from a low-dopping Luttinger liquid phase into a Luther-Emery liquid at a critical hole concentration $n_{crit}\approx 1/3$. In the opposite case, $J_{\perp}/t_{\perp}< 3 / \sqrt{2}$, there as a sequence of three Luttinger liquid phases (LLI, LLII and LLIII) as a function of hole dopping.Comment: 9 pages, 15 figure

CERTCOST – Ökonomische Analyse von Bio-Kontrollsystemen auf EU Ebene

The EU funded project CERTCOST proposes to combine the experience and knowledge of both researchers and SMEs to analyse the implementation of organic certification systems and to estimate all relevant expenditures or transaction costs for different certification systems along the organic food supply chain. Benefits of certification will also be analysed, using data on consumers’ recognition and willingness to pay for different organic logos and trademarks. Finally, recommendations will be drawn for the EU Commission, national competent authorities and private actors in organic food and farming on how to increase effectiveness and efficiency of organic certification