Results for "Stefan Wagner"

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A Geometric Approach to Noncommutative Principal BundlesAug 01 2011From a geometrical point of view it is, so far, not sufficiently well understood what should be a "noncommutative principal bundle". Still, there is a well-developed abstract algebraic approach using the theory of Hopf algebras. An important handicap ... More
Free Group Actions from the Viewpoint of Dynamical SystemsNov 23 2011In this paper we present a new characterization of free group actions (in classical differential geometry), involving dynamical systems and representations of the corresponding transformation groups. In fact, given a dynamical system, we provide conditions ... More
On Noncommutative Principal Bundles with Finite Abelian Structure GroupJan 09 2012Sep 09 2015Let $\Lambda$ be a finite abelian group. A dynamical system with transformation group $\Lambda$ is a triple $(A,\Lambda,\alpha)$, consisting of a unital locally convex algebra $A$, the finite abelian group $\Lambda$ and a group homomorphism $\alpha:\Lambda\rightarrow\Aut(A)$, ... More
Extending Characters of Fixed Point AlgebrasNov 23 2011Sep 09 2015A dynamical system is a triple $(A,G,\alpha)$, consisting of a unital locally convex algebra $A$, a topological group $G$ and a group homomorphism $\alpha:G\rightarrow\Aut(A)$, which induces a continuous action of $G$ on $A$. Further, a unital locally ... More
Secondary Characteristic Classes of Lie Algebra ExtensionsJul 26 2017We introduce a notion of secondary characteristic classes of Lie algebra extensions. As a spin-off of our construction we obtain a new proof of Lecomte's generalization of the Chern-Weil homomorphism.
A Geometric Approach to Noncommutative Principal Torus BundlesAug 22 2011Jan 07 2012A (smooth) dynamical system with transformation group $\mathbb{T}^n$ is a triple $(A,\mathbb{T}^n,\alpha)$, consisting of a unital locally convex algebra $A$, the $n$-torus $\mathbb{T}^n$ and a group homomorphism $\alpha:\mathbb{T}^n\rightarrow\Aut(A)$, ... More
Part III, Free Actions of Compact Quantum Groups on C*-AlgebrasJan 20 2017Aug 09 2017We study and classify free actions of compact quantum groups on unital C*-algebras in terms of generalized factor systems. Moreover, we use these factor systems to show that all finite coverings of irrational rotation C*-algebras are cleft.
Part II, Free Actions of Compact Groups on C*-AlgebrasAug 31 2015Jul 19 2017We study a simple subclass of free actions of non-Abelian groups on unital C*-algebras, namely cleft actions. These are characterized by the fact that the associated noncommutative vector bundles are trivial. In particular, we provide a complete classification ... More
Part I, Free Actions of Compact Abelian Groups on C*-AlgebrasMay 04 2015Jul 19 2017We study free and compact group actions on unital C*-algebras. In particular, we provide a complete classification theory of these actions for compact Abelian groups and explain its relation to the classical classification theory of principal bundles. ... More
Complex group rings of group extensionsNov 15 2018Nov 21 2018Let $N$ and $H$ be groups, and let $G$ be an extension of $H$ by $N$. In this article we describe the structure of the complex group ring of $G$ in terms of data associated with $N$ and $H$. In particular, we present conditions on the building blocks ... More
The Theory of Scanning Quantum Dot MicroscopyMay 15 2019Electrostatic forces are among the most common interactions in nature and omnipresent at the nanoscale. Scanning probe methods represent a formidable approach to study these interactions locally. The lateral resolution of such images is, however, often ... More
How Usable are Rust Cryptography APIs?Jun 13 2018Jul 18 2018Context: Poor usability of cryptographic APIs is a severe source of vulnerabilities. Aim: We wanted to find out what kind of cryptographic libraries are present in Rust and how usable they are. Method: We explored Rust's cryptographic libraries through ... More
Improving Communication in Scrum TeamsMar 31 2017Communication in teams is an important but difficult issue. In a Scrum development process, we use the Daily Scrum meetings to inform others about important problems, news and events in the project. When persons are absent due to holiday, illness or travel, ... More
Does Outside-In Teaching Improve the Learning of Object-Oriented Programming?Mar 30 2017Object-oriented programming (OOP) is widely used in the software industry and university introductory courses today. Following the structure of most textbooks, such courses frequently are organised starting with the concepts of imperative and structured ... More
Leadership Gap in Agile Teams: How Teams and Scrum Masters MatureDec 19 2018Motivation: How immature teams can become agile is a question that puzzles practitioners and researchers alike. Scrum is one method that supports agile working. Empirical research on the Scrum Master role remains scarce and reveals contradicting results. ... More
A model and sensitivity analysis of the quality economics of defect-detection techniquesDec 12 2016One of the main cost factors in software development is the detection and removal of defects. However, the relationships and influencing factors of the costs and revenues of defect-detection techniques are still not well understood. This paper proposes ... More
The Use of Application Scanners in Software Product Quality AssessmentNov 21 2016Software development needs continuous quality control for a timely detection and removal of quality problems. This includes frequent quality assessments, which need to be automated as far as possible to be feasible. One way of automation in assessing ... More
What Do Practitioners Vary in Using Scrum?Mar 30 2017Background: Agile software development has become a popular way of developing software. Scrum is the most frequently used agile framework, but it is often reported to be adapted in practice. Objective: Thus, we aim to understand how Scrum is adapted in ... More
Droplets on liquids and their long way into equilibriumDec 05 2012The morphological paths towards equilibrium droplets during the late stages of the dewetting process of a liquid film from a liquid substrate is investigated experimentally and theoretically. As liquids, short chained polystyrene (PS) and polymethyl-methacrylate ... More
Open Science in Software EngineeringApr 13 2019Open science describes the movement of making any research artefact available to the public and includes, but is not limited to, open access, open data, or open source. While open science is becoming generally accepted as a norm in other scientific disciplines, ... More
A Bayesian Network Approach to Assess and Predict Software Quality Using Activity-Based Quality ModelsNov 30 2016Context: Software quality is a complex concept. Therefore, assessing and predicting it is still challenging in practice as well as in research. Activity-based quality models break down this complex concept into concrete definitions, more precisely facts ... More
Scrum for cyber-physical systems: a process proposalMar 20 2017Agile development processes and especially Scrum are changing the state of the practice in software development. Many companies in the classical IT sector have adopted them to successfully tackle various challenges from the rapidly changing environments ... More
A Bayesian Network Approach to Assess and Predict Software Quality Using Activity-Based Quality Models (Conference Version)Nov 30 2016Assessing and predicting the complex concept of software quality is still challenging in practice as well as research. Activity-based quality models break down this complex con- cept into more concrete definitions, more precisely facts about the system, ... More
Lattice QCD investigation of a doubly-bottom $\bar{b} \bar{b} u d$ tetraquark with quantum numbers $I(J^P) = 0(1^+)$Apr 08 2019Apr 17 2019We use lattice QCD to investigate the spectrum of the $\bar{b} \bar{b} u d$ four-quark system with quantum numbers $I(J^P) = 0(1^+)$. We use five different gauge-link ensembles with $2+1$ flavors of domain-wall fermions, including one at the physical ... More
Bayesian Effect Selection in Structured Additive Distributional Regression ModelsFeb 27 2019We propose a novel spike and slab prior specification with scaled beta prime marginals for the importance parameters of regression coefficients to allow for general effect selection within the class of structured additive distributional regression. This ... More
Microservices Migration in Industry: Intentions, Strategies, and ChallengesJun 11 2019To remain competitive in a fast changing environment, many companies started to migrate their legacy applications towards a Microservices architecture. Such extensive migration processes require careful planning and consideration of implications and challenges ... More
Links between the personalities, styles and performance in computer programmingNov 30 2016There are repetitive patterns in strategies of manipulating source code. For example, modifying source code before acquiring knowledge of how a code works is a depth-first style and reading and understanding before modifying source code is a breadth-first ... More
Challenges of the Dynamic Detection of Functionally Similar Code FragmentsJan 18 2018Classic clone detection approaches are hardly capable of finding redundant code that has been developed independently, i.e., is not the result of copy&paste. To automatically detect such functionally similar code of independent origin, we experimented ... More
Assuring the Evolvability of Microservices: Insights into Industry Practices and ChallengesJun 12 2019While Microservices promise several beneficial characteristics for sustainable long-term software evolution, little empirical research covers what concrete activities industry applies for the evolvability assurance of Microservices and how technical debt ... More
A literature survey of the quality economics of defect-detection techniquesDec 14 2016Over the last decades, a considerable amount of empirical knowledge about the efficiency of defect-detection techniques has been accumulated. Also a few surveys have summarised those studies with different focuses, usually for a specific type of technique. ... More
Comparing Bug Finding Tools with Reviews and TestsNov 14 2017Bug finding tools can find defects in software source code us- ing an automated static analysis. This automation may be able to reduce the time spent for other testing and review activities. For this we need to have a clear understanding of how the defects ... More
An Activity-Based Quality Model for MaintainabilityJul 26 2017Maintainability is a key quality attribute of successful software systems. However, its management in practice is still problematic. Currently, there is no comprehensive basis for assessing and improving the maintainability of software systems. Quality ... More
Chiral Partners in a Chirally Broken WorldJul 15 2008The isovector--vector and the isovector--axial-vector current are related by a chiral transformation. These currents can be called chiral partners at the fundamental level. In a world where chiral symmetry was not broken, the corresponding current-current ... More
Noncommutative Coverings of Quantum ToriOct 25 2017We introduce a framework for coverings of noncommutative spaces. Moreover, we study noncommutative coverings of irrational quantum tori and characterize all such coverings that are connected in a reasonable sense.
Abstractness, specificity, and complexity in software designSep 05 2017Abstraction is one of the fundamental concepts of software design. Consequently, the determination of an appropriate abstraction level for the multitude of artefacts that form a software system is an integral part of software engineering. However, the ... More
The extended flare in CTA 102 in 2016 and 2017 within a hadronic model through cloud ablation by the relativistic jetNov 29 2018The flat spectrum radio quasar CTA 102 (redshift 1.037) exhibited a tremendously bright 4-months long outburst from late 2016 to early 2017. In a previous paper, we interpreted the event as the ablation of a gas cloud by the relativistic jet. The multiwavelength ... More
Free Actions of Compact Groups on C*-Algebras, Part IMay 04 2015Aug 04 2016We study free and compact group actions on unital C*-algebras. In particular, we provide a complete classification theory of these actions for compact abelian groups and explain its relation to the classical classification theory of principal bundles. ... More
A controlled experiment for the empirical evaluation of safety analysis techniques for safety-critical softwareDec 01 2016Context: Today's safety critical systems are increasingly reliant on software. Software becomes responsible for most of the critical functions of systems. Many different safety analysis techniques have been developed to identify hazards of systems. FTA ... More
Empirical Research Plan: Effects of Sketching on Program ComprehensionDec 05 2016Sketching is an important means of communication in software engineering practice. Yet, there is little research investigating the use of sketches. We want to contribute a better understanding of sketching, in particular its use during program comprehension. ... More
Integrating a Model of Analytical Quality Assurance into the V-Modell XTNov 04 2016Economic models of quality assurance can be an important tool for decision makers in software development projects. They enable to base quality assurance planning on economical factors of the product and the used defect-detection techniques. A variety ... More
A Systematic Review of Productivity Factors in Software DevelopmentJan 19 2018Analysing and improving productivity has been one of the main goals of software engineering research since its beginnings. A plethora of studies has been conducted on various factors that resulted in several models for analysis and prediction of productivity. ... More
Combining STPA and BDD for Safety Analysis and Verification in Agile Development: A Controlled ExperimentApr 05 2018Context: Agile development is in widespread use, even in safety-critical domains. Motivation: However, there is a lack of an ap- propriate safety analysis and verification method in agile development. Objective: In this paper, we investigate the use of ... More
Asheetoxy: A Taxonomy for Classifying Negative Spreadsheet-related PhenomenaAug 30 2018Spreadsheets (sometimes also called Excel programs) are powerful tools which play a business-critical role in many organizations. However, due to faulty spreadsheets many bad decisions have been taken in recent years. Since then, a number of researchers ... More
Is the Stack Distance Between Test Case and Method Correlated With Test Effectiveness?Mar 13 2019Mutation testing is a means to assess the effectiveness of a test suite and its outcome is considered more meaningful than code coverage metrics. However, despite several optimizations, mutation testing requires a significant computational effort and ... More
Third Group Cohomology and Gerbes over Lie GroupsFeb 08 2016Jun 29 2016The topological classification of gerbes, as principal bundles with the structure group the projective unitary group of a complex Hilbert space, over a topological space $H$ is given by the third cohomology $\text{H}^3(H, \Bbb Z)$. When $H$ is a topological ... More
The SE/MP Trade-off in Simulation Software Engineering: Examples and a Preliminary Systematic Literature ReviewAug 15 2016Large-scale simulations play a central role in science and the industry. Several challenges occur when building simulation software, because simulations require complex software developed in a dynamical construction process. That is why simulation software ... More
Free Actions of Compact Groups on C*-Algebras, Part IIAug 31 2015Aug 04 2016We study a simple subclass of free actions of non-Abelian groups on unital C*-algebras, namely cleft actions. These are characterized by the fact that the associated noncommutative vector bundles are trivial. In particular, we provide a complete classification ... More
Keeping Continuous Deliveries SafeDec 13 2016Allowing swift release cycles, Continuous Delivery has become popular in application software development and is starting to be applied in safety-critical domains such as the automotive industry. These domains require thorough analysis regarding safety ... More
The Extended Jet In AP Librae As The Source Of The VHE $γ$-ray EmissionNov 07 2016Most modeling attempts of blazars use a small emission zone located close to the central black hole in order to explain the broad-band spectral energy distribution. Here we present a case where additionally to the small region a $>$kpc-scale jet is required ... More
X-ray spectral studies of TeV gamma-ray emitting blazarsJan 27 2016This work is a summary of the X-ray spectral studies of 29 TeV $\gamma$-ray emitting blazars observed with Swift/XRT, especially focusing on sources for which X-ray regime allows to study the low and the high energy ends of the particle distributions ... More
Usability and Security Effects of Code Examples on Crypto APIs - CryptoExamples: A platform for free, minimal, complete and secure crypto examplesJul 03 2018Context: Cryptographic APIs are said to be not usable and researchers suggest to add example code to the documentation. Aim: We wanted to create a free platform for cryptographic code examples that improves the usability and security of created applications ... More
Interpolated energy densities, correlation indicators and lower bounds from approximations to the strong coupling limit of DFTMar 04 2017We investigate the construction of approximated exchange-correlation functionals by interpolating locally along the adiabatic connection between the weak- and the strong-coupling regimes, focussing on the effect of using approximate functionals for the ... More
The Long-Lasting Activity in the Flat Spectrum Radio Quasar (FSRQ) CTA~102Feb 28 2019The flat spectrum radio quasar CTA 102 ($z = 1.032$) went through a tremendous phase of variability. Since early 2016 the gamma-ray flux level has been significantly higher than in previous years. It was topped by a four month long giant outburst, where ... More
A Systematic and Semi-Automatic Safety-Based Test Case Generation Approach Based on Systems-Theoretic Process AnalysisDec 09 2016Software safety is a crucial aspect during the development of modern safety-critical systems. Software is becoming responsible for most of the critical functions of systems. Therefore, the software components in the systems need to be tested extensively ... More
Towards Continuous Integration and Continuous Delivery in the Automotive IndustryDec 13 2016Development cycles are getting shorter and Continuous Integration and Delivery are being established in the automotive industry. We give an overview of the peculiarities in an automotive deployment pipeline, introduce technologies used and analyze Tesla's ... More
Information on the structure of the a1 from tau decayJan 05 2008The decay $\tau\to \pi\pi\pi\nu$ is analysed using different methods to account for the resonance structure, which is usually ascribed to the a1. One scenario is based on the recently developed techniques to generate axial-vector resonances dynamically, ... More
One evaluation of model-based testing and its automationJan 24 2017Model-based testing relies on behavior models for the generation of model traces: input and expected output---test cases---for an implementation. We use the case study of an automotive network controller to assess different test suites in terms of error ... More
Tau decay and the structure of the a1Aug 16 2007Nov 20 2007We analyse the decay $\tau\to\pi\pi\pi\nu$ based on the recently developed techniques to generate axial-vector resonances dynamically. Under the assumption that the a1 is a coupled-channel meson-molecule, the spectral function is described surprisingly ... More
Stability of money: Phase transitions in an Ising economyOct 10 2001The stability of money value is an important requisite for a functioning economy, yet it critically depends on the actions of participants in the market themselves. Here we model the value of money as a dynamical variable that results from trading between ... More
Can clone detection support quality assessments of requirements specifications?Nov 15 2017Due to their pivotal role in software engineering, considerable effort is spent on the quality assurance of software requirements specifications. As they are mainly described in natural language, relatively few means of automated quality assessment exist. ... More
A Software Reliability Model Based on a Geometric Sequence of Failure RatesDec 12 2016Software reliability models are an important tool in quality management and release planning. There is a large number of different models that often exhibit strengths in different areas. This paper proposes a model that is based on a geometric sequence ... More
Suzaku Wide Band Analysis of the X-ray Variability of TeV Blazar Mrk 421 in 2006May 06 2009May 08 2009We present the results of X-ray observations of the well-studied TeV blazar Mrk 421 with the Suzaku satellite in 2006 April 28. During the observation, Mrk 421 was undergoing a large flare and the X-ray flux was variable, decreasing by ~ 50 %, from 7.8x10^{-10} ... More
Naming the Pain in Requirements Engineering: Design of a Global Family of Surveys and First Results from GermanyNov 15 2016Context: For many years, we have observed industry struggling in defining a high quality requirements engineering (RE) and researchers trying to understand industrial expectations and problems. Although we are investigating the discipline with a plethora ... More
Stabilizing Single Ni adatoms on a Two-dimensional Porous Titania Overlayer at the SrTiO$_3$(110) SurfaceApr 12 2018Nickel vapor-deposited on the SrTiO$_3$(110) surface was studied using scanning tunneling microscopy, photoemission spectroscopy (PES), and density functional theory calculations. This surface forms a (4 $\times$ 1) reconstruction, composed of a 2-D titania ... More
Statistics of optical intraday variability in a complete sample of radio-selected BL Lac objectsJun 06 1995We present a study of the intraday variability behaviour of a complete sample of radio-selected BL Lac objects taken from the 1 Jy catalogue. In 28 out of 34 BL Lac objects (82\%) we detected intraday variability. 7 objects were observed during several ... More
Constraints on cosmological parameters from the EBL attenuation of VHE spectra of extragalactic sourcesAug 31 2009The Extragalactic Background Light (EBL) causes attenuation of the VHE spectra of extragalactic sources, via pair-production. The amount of attenuation depends on the distance of the source, i.e. on the integration over the line of sight path taken by ... More
Long term lightcurve of the BL Lac object 1ES 0229+200 at TeV energiesSep 15 2015The high-frequency peaked BL Lac object 1ES 0229+200 (z = 0.14) was first detected in very high energy (VHE, E > 100 GeV) $\gamma$-rays by the H.E.S.S. (High Energy Stereoscopic System) collaboration in 2006. No flux variability was reported in the initial ... More
At Ease with Your Warnings: The Principles of the Salutogenesis Model Applied to Automatic Static AnalysisNov 23 2016The results of an automatic static analysis run can be overwhelming, especially for beginners. The overflow of information and the resulting need for many decisions is mentally tiring and can cause stress symptoms. There are several models in health care ... More
Naming the Pain in Requirements Engineering: Comparing Practices in Brazil and GermanyNov 28 2016As part of the Naming the Pain in Requirements Engineering (NaPiRE) initiative, researchers compared problems that companies in Brazil and Germany encountered during requirements engineering (RE). The key takeaway was that in RE, human interaction is ... More
The extended jet of AP Librae: Origin of the very high-energy gamma-ray emission?Feb 10 2016Feb 11 2016The low-frequency peaked BL Lac object (LBL) AP Librae exhibits very-high-energy (VHE, $E>100$GeV) $\gamma$-ray emission and hosts an extended jet, which has been detected in radio and X-rays. The jet X-ray spectral index implies an inverse Compton origin. ... More
A new strategy to select candidate blazars for VHE observationAug 31 2009A new strategy to select candidate blazars for VHE observations, that gives an inherently complete sample from an all-sky compilation (excluding a narrow region around the galactic plane) of GeV-bright blazars is presented. The strategy is based on selecting ... More
Supporting Defect Causal Analysis in Practice with Cross-Company Data on Causes of Requirements Engineering ProblemsFeb 13 2017[Context] Defect Causal Analysis (DCA) represents an efficient practice to improve software processes. While knowledge on cause-effect relations is helpful to support DCA, collecting cause-effect data may require significant effort and time. [Goal] We ... More
Spreadsheet Guardian: An Approach to Protecting Semantic Correctness throughout the Evolution of SpreadsheetsNov 30 2016Nov 30 2017Spreadsheets are powerful tools which play a business-critical role in many organizations. However, many bad decisions taken due to faulty spreadsheets show that these tools need serious quality assurance. Furthermore, while collaboration on spreadsheets ... More
Too Trivial To Test? An Inverse View on Defect Prediction to Identify Methods with Low Fault RiskNov 02 2018Background. Test resources are usually limited and therefore it is often not possible to completely test an application before a release. To cope with the problem of scarce resources, development teams can apply defect prediction to identify fault-prone ... More
Monitoring of the FSRQ PKS 1510-089 with H.E.S.SAug 02 2017The flat spectrum radio quasar (FSRQ) PKS 1510-089 (z=0.361) is known for its complex multiwavelength behavior. It has been monitored regularly at very high energy (VHE, $E>100\,$GeV) gamma-rays with H.E.S.S. since its discovery in 2009 in order to study ... More
Attenuation of TeV $γ$-rays by the starlight photon field of the host galaxyNov 21 2016The absorption of TeV $\gamma$-ray photons produced in relativistic jets by surrounding soft photon fields is a long-standing problem of jet physics. In some cases the most likely emission site close to the central black hole is ruled out because of the ... More
Managing Quality Requirements Using Activity-Based Quality ModelsNov 04 2016Managing requirements on quality aspects is an important issue in the development of software systems. Difficulties arise from expressing them appropriately what in turn results from the difficulty of the concept of quality itself. Building and using ... More
What Is the Best Way For Developers to Learn New Software Tools? An Empirical Comparison Between a Text and a Video TutorialMar 31 2017The better developers can learn software tools, the faster they can start using them and the more efficiently they can later work with them. Tutorials are supposed to help here. While in the early days of computing, mostly text tutorials were available, ... More
Spectral characteristics of Mrk 501 during the 2012 and 2014 flaring statesSep 15 2015Observations at Very High Energies (VHE, E > 100 GeV) of the BL Lac object Mrk 501 taken with the High Energy Stereoscopic System (H.E.S.S.) in four distinct periods between 2004 and 2014 are presented, with focus on the 2012 and 2014 flaring states. ... More
An Exploratory Study of Applying a Scrum Development Process for Safety-Critical SystemsMar 15 2017Apr 05 2018Agile techniques recently have received attention in developing safety-critical systems. However, a lack of empirical knowledge of performing safety assurance techniques in practice, especially safety analysis into agile development processes prevents ... More
Correlation between the synchrotron and the inverse-Compton components, in the longterm light curve of GeV blazarsAug 31 2009To explore the correlation in the GeV band (i.e. the inverse-Compton component) with the optical band (i.e. the synchrotron component) of blazars that are bright in high energies, the light curves of a number of blazars monitored with the Fermi Gamma-ray ... More
Will My Tests Tell Me If I Break This Code?Nov 22 2016Automated tests play an important role in software evolution because they can rapidly detect faults introduced during changes. In practice, code-coverage metrics are often used as criteria to evaluate the effectiveness of test suites with focus on regression ... More
Poster: Identification of Methods with Low Fault RiskMay 03 2018Test resources are usually limited and therefore it is often not possible to completely test an application before a release. Therefore, testers need to focus their activities on the relevant code regions. In this paper, we introduce an inverse defect ... More
PtSe2 grown directly on polymer foil for use as a robust piezoresistive sensorMar 28 2019Robust strain gauges are fabricated by growing PtSe2 layers directly on top of flexible polyimide foils. These PtSe2 layers are grown by low-temperature, thermally-assisted conversion of predeposited Pt layers. Under applied flexure the PtSe2 layers show ... More
Operationalised product quality models and assessment: The Quamoco approachNov 28 2016Software quality models provide either abstract quality characteristics or concrete quality measurements; there is no seamless integration of these two aspects. Reasons for this include the complexity of quality and the various quality profiles in different ... More
Do We Preach What We Practice? Investigating the Practical Relevance of Requirements Engineering Syllabi - The IREB CaseFeb 01 2019Feb 06 2019Nowadays, there exist a plethora of different educational syllabi for Requirements Engineering (RE), all aiming at incorporating practically relevant educational units (EUs). Many of these syllabi are based, in one way or the other, on the syllabi provided ... More
Rapid variability at very high energies in Mrk 501Sep 16 2015A major flaring state of the BL Lac object Mrk 501 was observed by the High Energy Stereoscopic System (H.E.S.S.) in June, 2014. Flux levels higher than one Crab unit were recorded and rapid variability at very high energies ($\sim$2-20 TeV) was revealed. ... More
Are There Functionally Similar Code Clones in Practice?Mar 28 2018Having similar code fragments, also called clones, in software systems can lead to unnecessary comprehension, review and change efforts. Syntactically similar clones can often be encountered in practice. The same is not clear for only functionally similar ... More
A Comprehensive Model of UsabilityDec 14 2016Usability is a key quality attribute of successful software systems. Unfortunately, there is no common understanding of the factors influencing usability and their interrelations. Hence, the lack of a comprehensive basis for designing, analyzing, and ... More
A comprehensive safety engineering approach for software-intensive systems based on STPADec 09 2016Formal verification and testing are complementary approaches which are used in the development process to verify the functional correctness of software. However, the correctness of software cannot ensure the safe operation of safety-critical software ... More
Are Comprehensive Quality Models Necessary for Evaluating Software Quality?Mar 13 2017The concept of software quality is very complex and has many facets. Reflecting all these facets and at the same time measuring everything related to these facets results in comprehensive but large quality models and extensive measurements. In contrast, ... More
Probing Convolutional Neural Networks for Event Reconstruction in γ-Ray Astronomy with Cherenkov TelescopesNov 16 2017A dramatic progress in the field of computer vision has been made in recent years by applying deep learning techniques. State-of-the-art performance in image recognition is thereby reached with Convolutional Neural Networks (CNNs). CNNs are a powerful ... More
Well-Ordered In Adatoms at the In$_2$O$_3$(111) Surface Created by Fe DepositionApr 12 2018Metal deposition on oxide surfaces usually results in adatoms, clusters, or islands of the deposited material, where defects in the surface often act as nucleation centers. Here an alternate configuration is reported. After the vapor deposition of Fe ... More
The VHE Gamma-Ray View of the FSRQ PKS~1510-089Mar 20 2019The flat spectrum radio quasar PKS 1510-089 is a monitored target in many wavelength bands due to its high variability. It was detected as a very-high-energy (VHE) $\gamma$-ray emitter with H.E.S.S. in 2009, and has since been a regular target of VHE ... More
Communication channels in safety analysis: An industrial exploratory case studyApr 24 2018Safety analysis is a predominant activity in developing safety-critical systems. It is a highly cooperative task among multiple functional departments due to the increasingly sophisticated safety-critical systems and close-knit development processes. ... More
Verlässliche Software im 21. JahrhundertDec 04 2018Software is the main innovation driver in many different areas, like cloud services, autonomous driving, connected medical devices, and high-frequency trading. All these areas have in common that they require high dependability. In this paper, we discuss ... More
Transitive endomorphisms with critical pointsAug 24 2016We show that a non-wandering endomorphism of the torus with invertible linear part without invariant directions and for which the critical points are in some sense generic is transitive. This improves a result of Andersson by allowing critical points ... More
Solving the LPN problem in cube-root timeJan 23 2012In this paper it is shown that given a sufficient number of (noisy) random binary linear equations, the Learning from Parity with Noise (LPN) problem can be solved in essentially cube root time in the number of unknowns. The techniques used to recover ... More
Faithful Tropicalization of Mumford Curves of Genus TwoAug 01 2014In the present paper, we investigate the question if the skeleton of a Mumford curve of genus two can be tropicalized faithfully in dimension three, i.e. if there exists an embedding of the curve in projective three space such that the tropicalization ... More
Eulerian Properties of Design Hypergraphs and Hypergraphs with Small Edge CutsMay 15 2019An Euler tour of a hypergraph is a closed walk that traverses every edge exactly once; if a hypergraph admits such a walk, then it is called eulerian. Although this notion is one of the progenitors of graph theory --- dating back to the eighteenth century ... More