@article{JosephSchummRummeletal., author = {Joseph, Saskia and Schumm, Michael and Rummel, Otmar and Soska, Alexander and Renschke, Michael and Mottok, J{\"u}rgen and Niemetz, Michael and Schroll-Decker, Irmgard}, title = {Teaching finite state machines with case method and role play}, series = {2014 IEEE Global Engineering Education Conference (EDUCON 2014) : Istanbul, Turkey, 3 - 5 April 2014}, journal = {2014 IEEE Global Engineering Education Conference (EDUCON 2014) : Istanbul, Turkey, 3 - 5 April 2014}, publisher = {IEEE}, doi = {10.1109/EduCon.2013.6530275}, pages = {1302 -- 1305}, abstract = {The professional requirements in Software Engineering have become highly volatile due to the complexities of project development and rapid and innovative changes occurring in the field. Therefore, the development of inter-personal and social competences has gained central importance in the training of software developers. This paper will present a concept allowing to acquire competences by using Case Method and Role Play as instruments in several lectures of Software Engineering. By approaching the issue of competence acquisition on a technical as well as on an educational and social level, life-long learning is facilitated and supported.}, language = {en} } @article{DeubzerMottokMargulletal., author = {Deubzer, Michael and Mottok, J{\"u}rgen and Margull, Ulrich and Niemetz, Michael and Wirrer, Gerhard}, title = {Efficient Scheduling of Reliable Automotive Multi-core Systems with PD² by Weakening ERfair Task System Requirements}, series = {Automotive Safety and Security}, journal = {Automotive Safety and Security}, pages = {53 -- 67}, abstract = {Partly Proportionate fair (Partly-Pfair) scheduling, which allows task migration at runtime and assigns each task processing time with regard to its weight, makes it possible to build highly efficient embedded multi-core systems. Due to its non-work-conserving behavior, which might leave the CPU idle even when tasks are ready to execute, tasks finish only shortly before their deadlines are reached. Benefits are lower task jitter, but additional workload, e.g. through interrupts, can lead to deadline violations. In this paper we present a work-conserving extension of Partly-Pfair scheduling, called PERfair scheduling and the algorithm P-ERfair-PD2 which applies Pfair modifications used for Partly-Pfair on the concept of ERfairness and PD2 policies. With a simulation based schedulability examination we show for multiple time base (MTB) task sets that P-ERfair- PD2 has the same performance as Partly-Pfair-PD2. Additionally, we show that P-ERfair- PD2 has a much higher robustness against perturbations, and therefore it is well suited for embedded domains, especially for the Automotive domain.}, language = {en} } @article{DeubzerSchillerMottoketal., author = {Deubzer, Michael and Schiller, Frank and Mottok, J{\"u}rgen and Niemetz, Michael and Margull, Ulrich}, title = {Effizientes Multicore-Scheduling in Eingebetteten Systemen - Teil 1: Algorithmen f{\"u}r zuverl{\"a}ssige Echtzeitsysteme}, series = {atp - Automatisierungstechnische Praxis}, journal = {atp - Automatisierungstechnische Praxis}, number = {9}, pages = {60 -- 67}, abstract = {Eingebettete Systeme unterliegen neben den funktionalen Anforderungen besonders nicht funktionalen Qualit{\"a}tsanforderungen wie Effizienz, Zuverl{\"a}ssigkeit und Echtzeitf{\"a}higkeit. Mit steigendem Bedarf an Rechenkapazit{\"a}t k{\"o}nnen bisherige Konzepte zur Leistungssteigerung von Singlecore-Systemen jedoch nicht mehr eingesetzt werden - der Umstieg auf Multicore-Systeme wird erforderlich. Im ersten Teil dieser Arbeit werden eine m{\"o}gliche Prozessorarchitektur f{\"u}r zuk{\"u}nftige Automotive Multicore-Systeme und die Abstraktion der Software f{\"u}r diese Systeme vorgestellt. Nach einer Klassifkation von Multicore-Scheduling-Algorithmen pr{\"a}sentieren wir exemplarisch einen Algorithmus mit statischer Taskallokation und einen Algorithmus mit dynamischer Taskallokation. Bei beiden Algorithmen handelt es sich um eine {\"U}berf{\"u}hrung theoretisch behandelter Algorithmen auf Automotive Systeme.}, language = {de} } @article{DeubzerSchillerMottoketal., author = {Deubzer, Michael and Schiller, Frank and Mottok, J{\"u}rgen and Niemetz, Michael and Margull, Ulrich}, title = {Effizientes Multicore-Scheduling in Eingebetteten Systemen - Teil 2: Ein simulationsbasierter Ansatz zum Vergleich von Scheduling-Algorithmen}, series = {atp - Automatisierungstechnische Praxis}, volume = {52}, journal = {atp - Automatisierungstechnische Praxis}, number = {10}, abstract = {Eingebettete Systeme unterliegen neben den funktionalen Anforderungen besonders nichtfunktionalen Qualit{\"a}tsanforderungen wie Effizienz, Zuverl{\"a}ssigkeit und Echtzeitf{\"a}higkeit. Mit steigendem Bedarf an Rechenkapazit{\"a}t k{\"o}nnen bisherige Konzepte zur Leistungssteigerung von Singlecore-Systemen jedoch nicht mehr eingesetzt werden - der Umstieg auf Multicore-Systeme wird erforderlich. Im zweiten Teil dieser Arbeit wird ein simulationsbasierter Ansatz zum Vergleich von Multicore-Scheduling-Algorithmen vorgestellt, mit dem Algorithmen f{\"u}r Multicore-Systeme mit voller Migration und dynamischer Task-Priorit{\"a}t untersucht werden. Wir erweitern diesen Ansatz um ein Verfahren zur Untersuchung einer Tasksetmenge mit stochastisch beschriebenen Eigenschaften und vergleichen ihn mit den im Teil 1 beschriebenen Algorithmen BinPacking-EDF und P-ERfair-PD² f{\"u}r eine Gruppe von Automotive Powertrain Systemen.}, language = {de} } @article{SchoepeHaenninenNiemetz, author = {Schoepe, Wilfried and H{\"a}nninen, Risto and Niemetz, Michael}, title = {Breakdown of Potential Flow to Turbulence Around a Sphere Oscillating in Superfluid 4He Above the Critical Velocity}, series = {Journal of low temperature physics}, volume = {178}, journal = {Journal of low temperature physics}, publisher = {Springer Nature}, doi = {10.1007/s10909-014-1265-7}, pages = {383 -- 391}, abstract = {The onset of turbulent flow around an oscillating sphere in superfluid 4He is known to occur at a critical velocity where is the circulation quantum and is the oscillation frequency. But it is also well known that initially in a first up-sweep of the oscillation amplitude, can be considerably exceeded before the transition occurs, thus leading to a strong hysteresis in the velocity sweeps. The velocity amplitude where the transition finally occurs is related to the density of the remanent vortices in the superfluid. Moreover, at temperatures below ca. 0.5 K and in a small interval of velocity amplitudes between and a velocity that is about 2 \% larger, the flow pattern is found to be unstable, switching intermittently between potential flow and turbulence. From time series recorded at constant temperature and driving force, the distribution of the excess velocities is obtained and from that the failure rate. Below 0.1 K we also can determine the distribution of the lifetimes of the phases of potential flow. Finally, the frequency dependence of these results is discussed.}, language = {en} } @article{SteinkirchnerFuhrmannNiemetz, author = {Steinkirchner, Alfons and Fuhrmann, Thomas and Niemetz, Michael}, title = {Channel Coded Processor for Enhanced Safety}, series = {International Journal of Future Computer and Communication (IJFCC)}, volume = {6}, journal = {International Journal of Future Computer and Communication (IJFCC)}, number = {2}, publisher = {International Association of Computer Science and Information}, address = {Singapore}, issn = {2010-3751}, doi = {10.18178/ijfcc.2017.6.2.489}, pages = {58 -- 62}, abstract = {Several concepts are known for improving processor safety, all of them having their pros and cons. Some are very resource intensive, others have limited capabilities regarding the provided error safety. In this paper we use research on channel coding of noisy communication channels known from communication theory as an analogy to random bit errors in processors. We incorporate this knowledge into processor design to suggest a new error correction concept by using channel coding in processors. The new concept of a Channel Coded Processor could provide effective implementation of redundancy by the channel coding that enables error correction. The concept could also create a complete chain of redundancy in all areas and components of the processor ranging from the code compiler through the processing hardware to the output of the information.}, language = {en} } @article{NiemetzHaenninenSchoepe, author = {Niemetz, Michael and H{\"a}nninen, Risto and Schoepe, Wilfried}, title = {On the Transition from Potential Flow to Turbulence Around a Microsphere Oscillating in Superfluid 4He}, series = {Journal of low temperature physics}, volume = {187}, journal = {Journal of low temperature physics}, number = {3-4}, publisher = {Springer Nature}, doi = {10.1007/s10909-017-1745-7}, pages = {195 -- 220}, abstract = {The flow of superfluid around a translationally oscillating sphere, levitating without mechanical support, can either be laminar or turbulent, depending on the velocity amplitude. Below a critical velocity that scales as and is temperature independent below 1 K, the flow is laminar (potential flow). Below 0.5 K, the linear drag force is caused by ballistic phonon scattering that vanishes as until background damping, measured in the empty cell, becomes dominant for K. Increasing the velocity amplitude above leads to a transition from potential flow to turbulence, where the large turbulent drag force varies as . In a small velocity interval \% above , the flow is unstable below 0.5 K, switching intermittently between both patterns. From time series recorded at constant temperature and driving force, the lifetimes of both phases are analyzed statistically. We observe metastable states of potential flow which, after a mean lifetime of 25 min, ultimately break down due to vorticity created by natural background radioactivity. The lifetimes of the turbulent phases have an exponential distribution, and the mean increases exponentially with . We investigate the frequency at which the vortex rings are shed from the sphere. Our results are compared with recent data of other authors on vortex shedding by moving a laser beam through a Bose-Einstein condensate. Finally, we show that our observed transition to turbulence belongs to the class of "supertransient chaos" where lifetimes of the turbulent states increase faster than exponentially.}, language = {en} }