German University of Technology in Oman
Muscat, Oman

The German University of Technology in Oman is a private university in Muscat, Sultanate of Oman and was established in 2007 in collaboration with RWTH Aachen University in Germany, one of the leading universities of technology in Europe.GUtech is the only German university on the Arabian Peninsula and the first private university in Oman to receive international accreditation for all its BSc programs. In the Academic Year 2013/2014 approximately 1100 students were enrolled in GUtech’s programs. Wikipedia.

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Holzbecher E.,German University of Technology in Oman
International Journal of Multiphysics | Year: 2016

The storage of supercritical CO2 in deep geological formations can be partitioned in three stages: diffusion, early and late convection. The mass transfer of gaseous CO2 into an underlying brine layer is determined by the relative relevance of interacting multiphysics processes at the interface and the build up of a boundary layer. Within the brine layer convection emerges as a multiphysics phenomenon of coupled flow and transport in porous media. For the characterization of the three stages we use numerical experiments with perturbations of a reference homogeneous situation. We explore the effect of different type and size of perturbations. The simulations show that the onset of the convection state depends strongly not only on the perturbations, but also on settings of the numerical method. Moreover it is found that the early convection state may consist of several peaks and is thus more complex than in the idealized simple concept of a single peak. For the late convection stage the decrease of the total mass transfer into the system is generally confirmed.

Heim B.,German University of Technology in Oman
Abhandlungen aus dem Mathematischen Seminar der Universitat Hamburg | Year: 2017

In this paper the image of the Saito–Kurokawa lift of level N with Dirichlet character is studied. We give a new characterization of this so called Maass Spezialschar of level N by symmetries involving Hecke operators related to (Formula presented.). We finally obtain for all prime numbers p local Maass relations. This generalizes known results for level (Formula presented.). © 2017 The Author(s)

Holzbecher E.,German University of Technology in Oman
Poromechanics 2017 - Proceedings of the 6th Biot Conference on Poromechanics | Year: 2017

The general description of solute transport in multiphase environments depends on assumptions not only concerning the interphase exchange, but also concerning transport processes within the phases. In case of equilibrium between phase concentrations the formulation can be simplified significantly by the introduction of additional factors (R-factors) for advection, diffusion and degradation processes. The mathematical derivation is a generalization of the concept of retardation factors, which is well established in porous medium studies. In the given description of general multiphase situation the characterizing Péclet number is determined by the interphase equilibrium - in contrast to the common concept of retardation factors. An application demonstration is given for a two-domain system, in which both sub-domains obey transport equations with different Péclet-numbers. It is shown that the concentration profile is very different in the sub-domains on both sides of the interface. © ASCE.

Barakat N.,German University of Technology in Oman | Bradley A.P.,Queensland University of Technology
Neurocomputing | Year: 2010

Over the last decade, support vector machine classifiers (SVMs) have demonstrated superior generalization performance to many other classification techniques in a variety of application areas. However, SVMs have an inability to provide an explanation, or comprehensible justification, for the solutions they reach. It has been shown that the '. black-box' nature of techniques like artificial neural networks (ANNs) is one of the main obstacles impeding their practical application. Therefore, techniques for rule extraction from ANNs, and recently from SVMs, were introduced to ameliorate this problem and aid in the explanation of their classification decisions. In this paper, we conduct a formal review of the area of rule extraction from SVMs. The review provides a historical perspective for this area of research and conceptually groups and analyzes the various techniques. In particular, we propose two alternative groupings; the first is based on the SVM (model) components utilized for rule extraction, while the second is based on the rule extraction approach. The aim is to provide a better understanding of the topic in addition to summarizing the main features of individual algorithms. The analysis is then followed by a comparative evaluation of the algorithms' salient features and relative performance as measured by a number of metrics. It is concluded that there is no one algorithm that can be favored in general. However, methods that are kernel independent, produce the most comprehensible rule set and have the highest fidelity to the SVM should be preferred. In addition, a specific method can be preferred if the context of the requirements of a specific application, so that appropriate tradeoffs may be made. The paper concludes by highlighting potential research directions such as the need for rule extraction methods in the case of SVM incremental and active learning and other application domains, where special types of SVMs are utilized. © 2010 Elsevier B.V.

Rupp F.,German University of Technology in Oman
Few-Body Systems | Year: 2015

Motivated by the continuous search for stable geometric configurations of atom and molecule clusters, we analyse the planar evolution of two freely movable point particles around a third immovable one subject to the 12-6-Lennard-Jones potential. This tailors our discussion to systems with one very heavy particle that can be assumed to be permanently at rest in the moving reference frame for the whole ensemble. Relating to Lennard-Jones interactions, we allow all three point particles to take different parameters. This breaks the symmetry conditions that are usually imposed on such systems. Through a classical non-regularized Hamiltonian description of our restricted three particle system, we study the existence of genuine equilibria and rigid rotor solutions around a single axis of rotation. We prove, depending on the choice of the Lennard-Jones parameters, that for these genuine equilibria, collinear alignments and triangular configurations of any shape can occur. Moreover, for the discussed type of relative equilibria a complete classification is provided by proving the existence of rigid rotor configurations in the plane of rotation (collinear cis and trans as well as triangle shaped configurations) and out of the plane of rotation (triangle shaped and flag-like configurations). Furthermore, we show that there are no further rigid rotor solutions of the underlying equations of motion. © 2015, Springer-Verlag Wien.

Abe S.,RWTH Aachen | Urai J.L.,RWTH Aachen | Urai J.L.,German University of Technology in Oman
Journal of Geophysical Research: Solid Earth | Year: 2012

We use discrete element model simulations to model the full boudinage process from initial fracturing of intact material to post-fracture flow of material into gaps between fragments and to investigate the role which the material properties of the weak and strong layers play in this process. The models are deformed in 2D plane strain under a range of confining stresses, in coaxial bulk flow. Results show that the material properties, i.e. Mohr-Coulomb or quasi-viscous for the matrix and elastic-brittle for the competent layer, lead to the development of natural looking boudin morphologies and deformation patterns in the matrix. The details of the matrix rheology only have a minor influence on the morphology of the boudins. By varying the material properties of the competent layer between fully brittle and semi-ductile we obtain a wide range of deformation patterns ranging from pinch-and-swell structures to a variety of boudin types including drawn, shear band and straight sided torn boudins. In a number of models we observe rotation of the boudin blocks despite the applied deformation being purely coaxial. These rotations are generally related to asymmetrical (rhombic) boudin shapes. Some features observed in natural boudins such as concave block faces or the formation of veins between fragments are not modeled because pore fluids are not yet included in our model. Copyright 2012 by the American Geophysical Union.

Weidlich O.,Wintershall Holding AG | Bernecker M.,German University of Technology in Oman
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2011

Sedimentological, palaeontological, and geochemical data of a 152-m thick composite section of the Saiq Formation were used to describe the facies associations and the nature of carbonate precipitation during the Late Permian-Early Triassic at the eastern rim of the Arabian Platform (Sultanate of Oman, Saih Hatat, WadiČaday). Changhsingian (Late Permian) platform carbonates, dominated by bryozoans, brachiopods and crinoids, are truncated by a mineralized discontinuity surface. The disappearance of Permian calcified metazoans, a negative δ13Ccarb excursion, and a sharp facies contrast collectively suggest that the Permian-Triassic boundary lies in this interval. Unfossiliferous siliciclastics with nodules of iron and manganese minerals on top of the unconformity were probably deposited during a phase when sea water was undersaturated with respect to calcium carbonate. After a gap, late Dienerian carbonate deposition started with abiotically precipitated lime mudstone and biotically induced microbialites having the lowest observed δ13Ccarb values (facies association A). Further up, 1-2m of bioclastic wacke- and grainstones with a positive δ13Ccarb excursion indicate a short-lived interval of biotically controlled carbonate precipitation (facies association B). The overlying sequence of siliciclastics, laminated or bioturbated dolomitized mudstone, microbialites, dolomitic siltstone, and black calcite, which is characterized by a 2nd negative δ13Ccarb shift, marks the return to biotically induced carbonate precipitation (facies associations C-D). The recrystallized black calcite at the top of the sequence is capped by a thick palaeosol and overlain by late Early to Middle Triassic cycles consisting of biotically precipitated carbonate. The facies development of the rim of the Arabian Platform differs from that of the interior in having a pronounced discontinuity at the Permian-Triassic boundary and an Early Triassic bioclastic carbonate unit sandwiched between abiotically precipitated carbonates. The observed lateral changes in carbonate precipitation across the Arabian Platform could have been caused by changes in oceanic circulation, such as episodic upwelling of deep water. © 2010 Elsevier B.V.

Jabeur N.,German University of Technology in Oman
Procedia Computer Science | Year: 2016

Bio-inspired algorithms have been widely used to solve Wireless Sensor Network (WSN) challenges. In several studies, they have demonstrated effective capabilities to fulfil the expected goals while adapting to contextual changes and using limited resources. In this paper, we propose a new firefly-based approach for WSN clustering. Our approach includes a micro clustering phase during which sensors self-organize into clusters. These clusters are polished during a macro-clustering phase where they compete to integrate small neighboring clusters. Our simulations show promising results where the number of clusters tend to stabilize independently from the density of the network and the various communication ranges of sensors. © 2016 The Authors.

Holzbecher E.,German University of Technology in Oman
2016 3rd MEC International Conference on Big Data and Smart City, ICBDSC 2016 | Year: 2016

In urban areas the subsurface is utilized in many ways for various purposes. Integrated smart tools and data management is needed in order to synchronize different utilizations. These include monitoring, data transfer and storage, data processing (in particular: modelling), visualization and optimization. Integrating such tools is crucial for decision makers and good management of the subsurface. There is an overlap with smart water management in cities, in which groundwater has an important share on water supply. © 2016 IEEE.

Holzbecher E.,German University of Technology in Oman
Toxicological and Environmental Chemistry | Year: 2016

In multi-phase environments, for example in porous media, and particularly in groundwater and in sediments, the spatial and temporal distribution of a chemical or biological species is usually described by a set of multiple coupled differential equations. Under the conditions that an isotherm exists, the set of equations can be simplified to a single equation. The most well-known application of such a procedure in a fluid-solid system leads to the equation for retarded transport with the retardation factor R. As a generalization of this mathematical concept, factors Rdecay, Radv and Rdiff are introduced, which for general situations appear as factors in the single differential equation. The Peclet and Damkoehler numbers depend on these generalized retardation factors. They may also have an effect on the steady state solution - in contrast to the classical retardation factor R. Due to the reduction to a single equation, analytical and numerical tools that are well established for single-phase environments can be utilized. As an example for the application of the presented approach, the case of aquatic sediments is presented, for which the generalized concept allows to study solute transport considering processes like compaction, bioirrigation and bioturbation in addition to the common fluid phase processes. © 2016 Informa UK Limited, trading as Taylor & Francis Group

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