@unpublished{GoeppelFrikelHaltmeier, author = {G{\"o}ppel, Simon and Frikel, J{\"u}rgen and Haltmeier, Markus}, title = {A complementary ℓ1 -TV reconstruction algorithm for limited data CT}, abstract = {In a variety of tomographic applications, data cannot be fully acquired, leading to severely underdetermined image reconstruction. Conventional methods result in reconstructions with significant artifacts. In order to remove these artifacts, regularization methods have to be applied that incorporate additional information. An important example is TV reconstruction which is well known to efficiently compensate for missing data and well reduces reconstruction artifacts. At the same time, however, tomographic data is also contaminated by noise, which poses an additional challenge. The use of a single regularizer within a variational regularization framework must therefore account for both the missing data and the noise. However, a single regularizer may not be ideal for both tasks. For example, the TV regularizer is a poor choice for noise reduction over different scales, in which case ℓ1 curvelet regularization methods work well. To address this issue, in this paper we introduce a novel variational regularization framework that combines the advantages of two different regularizers. The basic idea of our framework is to perform reconstruction in two stages, where the first stage mainly aims at accurate reconstruction in the presence of noise, and the second stage aims at artifact reduction. Both reconstruction stages are connected by a data proximity condition. The proposed method is implemented and tested for limited-view CT using a combined curvelet-TV approach. We define and implement a curvelet transform adapted to the limited view problem and demonstrate the advantages of our approach in a series of numerical experiments in this context.}, language = {en} } @inproceedings{BorgSauerJorgensenFrikeletal., author = {Borg, Leise and Sauer J{\o}rgensen, Jakob and Frikel, J{\"u}rgen and Todd Quinto, Eric and Sporring, Jon}, title = {Reducing artifacts from varying projection truncations}, series = {3rd International Conference on Tomography of Materials and Structures Lund, Sweden, 26-30 June 2017, ICTMS2017-65-1}, booktitle = {3rd International Conference on Tomography of Materials and Structures Lund, Sweden, 26-30 June 2017, ICTMS2017-65-1}, abstract = {We study samples with full and partial occlusion causing streak artifacts, and propose two mod-ifications of filtered backprojection for artifact removal. Data is obtained by the SPring-8 synchrotron using a monochromatic parallel-beam scan [1]. Thresholding in the sinogram segments the metal, resulting in edges on which we apply 1) a smooth transition, or 2) a Dirichlet boundary condition.}, language = {en} } @misc{FrikelGoeppelHaltmeier, author = {Frikel, J{\"u}rgen and G{\"o}ppel, Simon and Haltmeier, Markus}, title = {Combining reconstruction and edge detection in CT}, series = {BVM Workshop 2023, 02.-04. Juli 2023, Braunschweig}, journal = {BVM Workshop 2023, 02.-04. Juli 2023, Braunschweig}, abstract = {We present two methods that combine image reconstruction and edge detection in computed tomography (CT) scans. Our first method is as an extension of the prominent filtered backprojection algorithm. In our second method we employ ℓ1-regularization for stable calculation of the gradient. As opposed to the first method, we show that this approach is able to compensate for undersampled CT data.}, language = {en} } @inproceedings{FrikelQuinto, author = {Frikel, J{\"u}rgen and Quinto, E.T.}, title = {Artifacts in limited view tomography}, series = {Oberwolfach Reports}, volume = {11}, booktitle = {Oberwolfach Reports}, number = {3}, editor = {Burger, Martin and Todd Quinto, Eric and Louis, Alfred K.}, doi = {10.4171/OWR/2014/37}, pages = {2047 -- 2114}, language = {en} } @inproceedings{GalkaSchuhegger, author = {Galka, Stefan and Schuhegger, Lukas}, title = {Integration of Discrete-event Simulation in the Planning of a Hydrogen Electrolyzer Production Facility}, series = {Proceedings of the 2022 Winter Simulation Conference (WSC), 11-14 Dec. 2022, Singapore}, booktitle = {Proceedings of the 2022 Winter Simulation Conference (WSC), 11-14 Dec. 2022, Singapore}, editor = {Feng, B. and Pedrielli, G. and Peng, Y. and Shashaani, S. and Song, E. and Corlu, C.G. and Lee, L.H. and Chew, E.P. and Roeder, T. and Lendermann, P.}, publisher = {IEEE}, address = {Singapore}, pages = {2}, abstract = {In the context of production and factory planning, the expansion of the factory must already be taken into account during initial planning. This results in an increase in planning complexity, as the involved planners have to know the expansion stages of the factory in the different time periods and have to evaluate concept modifications across all time periods. This paper presents an idea for a planning tool, which takes expansion stages into consideration. The data model contains all relevant information to generate a simulation model of the factory in an almost automated way. The aim is to enable factory planners to quickly investigate concept changes with the help of simulation, for example, to identify bottlenecks.}, language = {en} } @misc{WildGalkaWappleretal., author = {Wild, Tobias and Galka, Stefan and Wappler, Mona and Xing, Lu}, title = {Integrating supply chain aspects into factory planning, a simulation approach}, series = {The journey to sustainable supply chains: proceedings of the 26th International Symposium on Logistics (ISL 2022), 10-13th July 2022, Cork, Ireland}, journal = {The journey to sustainable supply chains: proceedings of the 26th International Symposium on Logistics (ISL 2022), 10-13th July 2022, Cork, Ireland}, editor = {Potter, A. and Pawar, K. S. and O'Reilly, S. and Jimo, A.}, publisher = {Nottingham University Business School, UK}, address = {Nottingham, UK}, isbn = {978-0-85358-350-9}, pages = {6}, abstract = {One major goal of green-field factory planning is to decide on space requirements in the plant. In this phase, detailed information about the supply chain network (e.g. which suppliers deliver which parts) is often unavailable. Nevertheless, typical decisions in supply chain management, like the definition of replenishment processes and quantities or make-or-buy decisions, impact space requirements in the factory and should therefore be considered in the factory planning. This research article proposes a simulation approach for a factory simulation in which raw material replenishment is integrated to evaluate the space requirements for raw materials.}, language = {de} } @inproceedings{SchmidWildSchneidewindetal., author = {Schmid, Florian and Wild, Tobias and Schneidewind, Jan and Vogl, Tobias and Schuhegger, Lukas and Galka, Stefan}, title = {Simulation Based Approach for Reconfiguration and Ramp up Scenario Analysis in Factory Planning}, series = {Proceedings of the 2022 Winter Simulation Conference (WSG), 11-14 Dec. 2022, Singapore}, booktitle = {Proceedings of the 2022 Winter Simulation Conference (WSG), 11-14 Dec. 2022, Singapore}, publisher = {IEEE}, isbn = {978-1-6654-7661-4}, doi = {10.1109/WSC57314.2022.10015310}, pages = {2842 -- 2852}, abstract = {Structural changes in production entail a potential economic risk for manufacturing companies. It is necessary to identify a suitable strategy for the reconfiguration process and to continue to meet the demand during the change in the factory structure and ramp-up phase. A simulation offers the possibility to analyze different ramp-up scenarios for the factory structure and to select a suitable concept for the reconfiguration process. A discrete event simulation approach is presented that can be used to evaluate variants of structural changes and serves as a basis for deciding on a reconfiguration strategy. This approach is demonstrated using a specific production step of a plant producing hydrogen electrolyzers, the results and generalized conclusions are discussed.}, language = {en} } @incollection{Weber, author = {Weber, Karsten}, title = {Robotik in der Pflege- und Gesundheitsversorgung}, series = {Genese und Folgen der Pflegerobotik}, booktitle = {Genese und Folgen der Pflegerobotik}, number = {196}, editor = {Hergesell, J. and Meister, M. and Maibaum, A.}, publisher = {Beltz/Juventa}, address = {Weinheim}, isbn = {978-3-7799-5243-5}, abstract = {Drei Ver{\"a}nderungen charakterisieren den demografischen Wandel in Deutschland: steigende durchschnittliche Lebenserwartung, der Anteil der Alten und Hochbetagten w{\"a}chst und der Anteil der j{\"u}ngeren Generationen schrumpft. Konsequenzen sind ein Zuwachs chronisch-degenerativer und pflegeintensiver Erkrankungen, ein schrumpfendes Arbeitskr{\"a}ftepotenzial und vor der {\"U}berlastung stehende soziale Sicherungssysteme. Abhilfe soll durch verst{\"a}rkten Technikeinsatz in der Pflege, insbesondere durch Roboter, geleistet werden: Roboter sollen Pflegekr{\"a}fte erg{\"a}nzen oder ersetzen, um dem Pflegenotstand zu begegnen und die Kosten der Pflege zu senken. Damit gehen aber zahlreiche Herausforderungen einher, die nicht zuletzt ethische Fragen ber{\"u}hren: Eine durch Technik bzw. Roboter gest{\"u}tzte Pflege wird diese in ihrem Kern ver{\"a}ndern, Professions- und Menschenbilder werden infrage gestellt und moralische Anspr{\"u}che tangiert. Der Beitrag zeichnet diese Gemengelage nach und skizziert ein diskursethisch ausgerichtetes Verfahren (MEESTAR) zur Aushandlung der Bedingungen f{\"u}r den Robotereinsatz in der Pflege- und Gesundheitsversorgung.}, language = {de} } @article{Weber, author = {Weber, Karsten}, title = {Computers as omnipotent instruments of power}, series = {The ORBIT Journal - An Online Journal for Responsible Research and Innovation in ICT}, volume = {2}, journal = {The ORBIT Journal - An Online Journal for Responsible Research and Innovation in ICT}, number = {1}, publisher = {Elsevier}, doi = {10.29297/orbit.v2i1.97}, pages = {1 -- 19}, abstract = {With examples concerning the development and dissemination of computer technology in the Soviet Union, the U.S., and other Western countries it shall be demonstrated that computer development on the one hand and social change as well as changes in policy making and administration on the other hand are mingled with each other without a clear direction of causation being discernible.It also shall be shown that perceived social and political threats imposed by early computer technology sometimes actually helped to stop or at least slow down social change. One conclusion that can be drawn from the case studies described for RRI is that the conscious steering of innovations fails because of diffuse and uncoordinated resistance from very different stakeholders. The case studies also suggest that the effectiveness of RRI might be rather limited.}, language = {en} } @incollection{KleineUlbrichtWeberetal., author = {Kleine, Nadine and Ulbricht, Max-R. and Weber, Karsten and Pallas, Frank}, title = {Participatory Sensing und Wearable Technologies als partizipative Formen der Datengenerierung im Internet of Things}, series = {'Grand Challenges' meistern - der Beitrag der Technikfolgenabsch{\"a}tzung}, booktitle = {'Grand Challenges' meistern - der Beitrag der Technikfolgenabsch{\"a}tzung}, editor = {Decker, Michael and Lindner, Ralf and Lingner, Stephan and Scherz, Constanze and Sotoudeh, Mahshid}, publisher = {Nomos}, address = {Baden-Baden}, doi = {10.5771/9783845283562-245}, pages = {245 -- 257}, subject = {Wearable Computer}, language = {de} } @article{Weber, author = {Weber, Karsten}, title = {Vorausschau und Regulierung von Innovationsprozessen im Bereich der ubiquit{\"a}ren Informations- und Kommunikationstechnologie}, series = {Modern Management Review / Dawna Nazwa - Zardądzanie i Marketing}, volume = {20}, journal = {Modern Management Review / Dawna Nazwa - Zardądzanie i Marketing}, number = {3}, doi = {10.7862/rz.2013.mmr.39}, abstract = {On the one hand technological innovations can create new markets and can provide for solutions of current social problems; on the other hand the can raise questions concerning environmental and/or social adequacy on short-, middle-, and long-range time scales. In or-der to strengthen the positive outcomes of innovations and to reduce or even prevent nega-tive effects, the task of technology assessment is to predict the positive as well as the nega-tive effects and repercussions of innovations as early as possible. However, it must be pre-supposed that first, it must be possible to make to a certain extent reliable predications about the future development and second, that regulatory measurements in order to strengthen the positive outcomes of innovations and to reduce or even prevent negative effects will find their respective addressees. But if one takes, for instance, ubiquitous information and com-munication technology into account it can be demonstrated that those conditions rarely can be met. This is the result of the types of innovation which take place in case of ICT as well as of the so-called Collingridge dilemma. Both factors reduce the reliability of predictions. Furthermore, regulatory measurements often do not find their addressees since the borders of the societal subsystems in which innovation take place are blurring and therefore, these subsystems often cannot be reached with mainstream regulatory approaches like laws.}, language = {de} } @article{WeberKleinePallasetal., author = {Weber, Karsten and Kleine, Nadine and Pallas, Frank and Ulbricht, Max-R.}, title = {Technik zur Unterst{\"u}tzung von Citizen Science und Open Science}, series = {TATuP - Zeitschrift f{\"u}r Technikfolgenabsch{\"a}tzung in Theorie und Praxis}, volume = {26}, journal = {TATuP - Zeitschrift f{\"u}r Technikfolgenabsch{\"a}tzung in Theorie und Praxis}, number = {1/2}, doi = {10.14512/tatup.26.1-2.25}, pages = {25 -- 30}, abstract = {If citizens actively participate in the process of collecting empirical data, as a key element of empirically oriented scientific projects, this can be seen as a contribution to an open and citizen-oriented science. Such participation can be supported by providing technical tools. The paper therefore presents examples of participatory sensing as the provision of affordable sensors for measuring environmental parameters as well as wearable technologies for recording quantified vital data and physiological states. Conceptually, the provision of data collected with these tools can be understood as a commons - with all opportunities and risks associated with such goods. After describing examples of participatory sensing and wearable technologies, the authors identify potential challenges and outline technical and organizational approaches to solve them.}, language = {de} } @article{Weber, author = {Weber, Karsten}, title = {What is it like to encounter an autonomous artificial agent?}, series = {AI \& Society}, volume = {28}, journal = {AI \& Society}, number = {4}, doi = {10.1007/s00146-013-0453-3}, pages = {483 -- 489}, abstract = {Following up on Thomas Nagel's paper "What is it like to be a bat?" and Alan Turing's essay "Computing machinery and intelligence," it shall be claimed that a successful interaction of human beings and autonomous artificial agents depends more on which characteristics human beings ascribe to the agent than on whether the agent really has those characteristics. It will be argued that Masahiro Mori's concept of the "uncanny valley" as well as evidence from several empirical studies supports that assertion. Finally, some tentative conclusions concerning moral implications of the arguments presented here shall be drawn}, language = {en} } @article{Weber, author = {Weber, Karsten}, title = {Technik in der Pflege}, series = {Evangelium und Wissenschaft}, volume = {39}, journal = {Evangelium und Wissenschaft}, number = {1}, language = {de} } @incollection{WeberKleine, author = {Weber, Karsten and Kleine, Nadine}, title = {Cybersecurity in Health Care}, series = {The Ethics of Cybersecurity}, volume = {21}, booktitle = {The Ethics of Cybersecurity}, editor = {Christen, Markus and Gordijn, Bert and Loi, Michele}, publisher = {Springer Nature}, address = {Cham, Switzerland}, isbn = {978-3-030-29053-5}, doi = {10.1007/978-3-030-29053-5_7}, pages = {139 -- 156}, abstract = {Ethical questions have always been crucial in health care; the rapid dissemination of ICT makes some of those questions even more pressing and also raises new ones. One of these new questions is cybersecurity in relation to ethics in health care. In order to more closely examine this issue, this chapter introduces Beauchamp and Childress' four principles of biomedical ethics as well as additional ethical values and technical aims of relevance for health care. Based on this, two case studies—implantable medical devices and electronic Health Card—are presented, which illustrate potential conflicts between ethical values and technical aims as well as between ethical values themselves. It becomes apparent that these conflicts cannot be eliminated in general but must be reconsidered on a case-by-case basis. An ethical debate on cybersecurity regarding the design and implementation of new (digital) technologies in health care is essential.}, language = {en} } @incollection{Weber, author = {Weber, Karsten}, title = {Technik in der Pflege: Bestandsaufnahme, Entwicklungsm{\"o}glichkeiten und normative Bewertung}, series = {Neue Technologien f{\"u}r die Pflege ; grundlegende Reflexionen und pragmatische Befunde}, booktitle = {Neue Technologien f{\"u}r die Pflege ; grundlegende Reflexionen und pragmatische Befunde}, number = {174}, editor = {H{\"u}lsken-Gießler, M. and Kreutzer, Susanne and D{\"u}tthorn, Nadin}, publisher = {Vandenhoeck \& Ruprecht}, address = {G{\"o}ttingen}, isbn = {978-3-7370-1202-7}, doi = {10.14220/9783737012027.153}, language = {de} } @inproceedings{DuennweberStadlerWeikletal., author = {D{\"u}nnweber, Jan and Stadler, Timo and Weikl, Sandra and Sch{\"a}fer, Andreas and Georg, Peter and Wein, Simon}, title = {Bus Route Classification for Rural Areas using Graph Convolutional Networks}, series = {Proceedings of the 22th International Conference on Artificial Intelligence and Soft Computing, Zakopane, Poland}, booktitle = {Proceedings of the 22th International Conference on Artificial Intelligence and Soft Computing, Zakopane, Poland}, pages = {15}, abstract = {In this paper, we present a new approach to determine the estimated time of arrival (ETA) for bus routes using (Deep) Graph Convolutional Networks (DGCNs). In addition we use the same DGCN to detect detours within a route. In our application, a classification of routes and their underlying graph structure is performed using Graph Learning. Our model leads to a fast prediction and avoids solving the vehicle routing problem (VRP) through expensive computations. Moreover, we describe how to predict travel time for all routes using the same DGCN Model. This method makes it possible not to use a more computationally intensive approximation algorithm when determining long travel times with many intermediate stops, but to use our network for an early estimate of the quality of a route. Long travel times, in our case result from the use of a call-bus system, which must distribute many passengers among several vehicles and can take them to places without a regular stop. For a case study, the rural town of Roding in Bavaria is used. Our training data for this area results from an approximation algorithm that we implemented to optimize routes, and to generate an archive of routes of varying quality simultaneously.}, language = {en} } @inproceedings{MuellerAltDuennweberetal., author = {M{\"u}ller, Jens and Alt, Martin and D{\"u}nnweber, Jan and Gorlatch, Sergei}, title = {Clayworks}, series = {IEEE International Conference on e-Science and Grid Computing (e-Science'06), 2nd, 4-6 Dec 2006, Amsterdam, Netherlands}, booktitle = {IEEE International Conference on e-Science and Grid Computing (e-Science'06), 2nd, 4-6 Dec 2006, Amsterdam, Netherlands}, isbn = {0-7695-2734-5}, doi = {10.1109/E-SCIENCE.2006.261188}, abstract = {Clayworks is a software system which integrates collaborative real-time modeling and distributed computing. It addresses the challenge of developing a collaborative workspace with a seamless access to high-performance servers. Clayworks allows modeling of virtual clay objects and running computation-intensive deformation simulations for objects crashing into each other. To integrate heterogeneous computational resources, we adopted modern Grid middleware and provided the users with an intuitive graphical interface. We parallelized the computation of simulations using a Higher-Order Component (HOC) which abstracts over the Globus Web service resource framework (WSRF) used to interconnect our worksuite to the computation server. Clayworks is a representative of a large class of demanding systems which combine collaborative modeling with performance-critical computations, e.g., crash-tests or simulations for biological population evolution.}, language = {en} } @incollection{DuennweberDumitrescuRaicuetal., author = {D{\"u}nnweber, Jan and Dumitrescu, Cǎtǎlin L. and Raicu, Ioan and Foster, Ian}, title = {Simplifying Grid Application Programming Using Web-Enabled Code Transfer Tools}, series = {Towards Next Generation Grids}, booktitle = {Towards Next Generation Grids}, editor = {Priol, Thierry and Vanneschi, Marco}, publisher = {Springer}, address = {Rennes, France}, isbn = {978-0-387-72497-3}, doi = {10.1007/978-0-387-72498-0_21}, pages = {225 -- 235}, abstract = {This paper deals with one of the fundamental properties of grid computing - transferring code between grid nodes and executing it remotely on heterogeneous hosts. Contemporary middleware relies for this purpose on Web Services, which makes application programs complicated and low-level and requires much additional expertise from programmers. We compare two mechanisms for grid application programming with regard to their handling of code transfer - the de-facto standard WS-GRAM in Globus and the higher-level approach based on HOCs (Higher-Order Components). We study the advantages and problems of each approach using a real-world application case study - the sequent alignment problem from bioinformatics. Our experiments show the trade-off between reduced development costs and software complexity when HOCs are used and the higher performance of the applications on the grid when using WS-GRAM.}, language = {en} } @inproceedings{DuennweberGorlatchBenoitetal., author = {D{\"u}nnweber, Jan and Gorlatch, Sergei and Benoit, Anne and Cole, Murray}, title = {Integrating MPI-Skeletons with Web Services}, series = {ParCo'05 - International Conference on Parallel Computing, 2005, Malaga, Spain}, booktitle = {ParCo'05 - International Conference on Parallel Computing, 2005, Malaga, Spain}, pages = {787 -- 794}, abstract = {Interoperating components, implemented in multiple programming languages, are one of the key requirements of grid computing that operates over the borders of individual hardware and software platforms. Modern grid middleware like WSRF facilitates interoperability through service-orientation but it also increases software complexity. We show that Higher-Order Components (HOCs) provide a service-oriented programming abstraction over middleware technology. By offering the pipeline skeleton from the MPI-based eSkel library as a HOC, we show how machine-oriented technologies can be made available via Web Services on grids. We bind a Java-based Web application to the HOC to demonstrate its connectivity: user defined input can be transformed in a highly performant manner by running wavelet computations remotely on parallel machines.}, language = {en} } @inproceedings{StadlerHofmeisterDuennweber, author = {Stadler, Timo and Hofmeister, Simon and D{\"u}nnweber, Jan}, title = {A Method for the Optimized Placement of Bus Stops Based on Voronoi Diagrams}, series = {Proceedings of the 55th Hawaii International Conference on System Sciences (HICSS55): January 3-7, 2022, Maui, Hawaii, USA}, booktitle = {Proceedings of the 55th Hawaii International Conference on System Sciences (HICSS55): January 3-7, 2022, Maui, Hawaii, USA}, doi = {10.24251/HICSS.2022.694}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-21214}, pages = {5686 -- 5694}, abstract = {In this paper a new method for placing bus stops is presented. The method is suitable for permanently installed new bus stops and temporarily chosen collection points for call busses as well. Moreover, our implementation of the Voronoi algorithm chooses new locations for bus stops in such a way that more bus stops are set in densely populated areas and less in less populated areas. To achieve this goal, a corresponding weighting is applied to each possible placement point, based on the number of inhabitants around this point and the points of interest, such as medical centers and department stores around this point. Using the area of Roding, a small town in Bavaria, for a case study, we show that our method is especially suitable for for rural areas, where there are few multi-family houses or apartment blocks and the area is not densely populated.}, language = {en} } @incollection{DuennweberLuedekingGorlatch, author = {D{\"u}nnweber, Jan and L{\"u}deking, Philipp and Gorlatch, Sergei}, title = {A Higher-Order Component for Efficient Genome Processing on the Grid}, series = {Making Grids Work}, booktitle = {Making Grids Work}, editor = {Danelutto, Marco and Fragopoulou, Paraskevi and Getov, Vladimir}, publisher = {Springer}, address = {Boston, MA}, isbn = {978-0-387-78447-2}, doi = {10.1007/978-0-387-78448-9_28}, pages = {351 -- 362}, abstract = {Computational grids combine computers in the Internet for distributed data processing and are an attractive platform for the data-intensive applications of bioinformatics. We present an extensible genome processing software for the grid and evaluate its performance. Our software was able to discover previously unknown circular permutations (CP) in the ProDom database containing more than 70MB of protein data. A specific feature of our software is its design as a component: the Alignment HOC, a Higher-Order Component that makes use of the latest Globus toolkit as grid middleware. Besides genome data, the Alignment HOC accepts plugin code for processing this data as its input, and contains all the required configuration to run the component on top of Globus, thus, freeing the non-grid-expert user from dealing with grid middleware. Instead of writing data distribution procedures and configuring the middleware appropriately for every new algorithm, Alignment HOC users reuse the existing component and only write application-specific plugins. To maintain plugins persistently in a reusable manner, we built a web-accessible plugin database with a comfortable administration GUI. The flexible component-based implementation makes it easy to study CPs in other databases (e.g. UniProt/Swiss-Prot) or to use an alignment algorithm different than the standard Needleman-Wunsch. For the efficient distribution of workload, we developed a library of group communication operations for HOCs.}, language = {en} } @incollection{DuennweberTomasoniGorlatchetal., author = {D{\"u}nnweber, Jan and Tomasoni, Johannes and Gorlatch, Sergei and Claßen, Michael and Claßen, Philipp and Lengauer, Christian}, title = {A Grid Component with Embedded Loop Parallelization}, series = {Grid Computing}, booktitle = {Grid Computing}, editor = {Gorlatch, Sergei and Fragopoulou, Paraskevi and Priol, Thierry}, publisher = {Springer}, address = {Berlin}, isbn = {978-0-387-09456-4}, doi = {10.1007/978-0-387-09457-1_22}, pages = {261 -- 273}, abstract = {This work integrates two distinct research areas of parallel and distributed computing, (1) automatic loop parallelization, and (2) component-based Grid programming. The latter includes technologies developed within CoreGRID for simplifying Grid programming: the Grid ComponentModel (GCM) and Higher- Order Components (HOCs). Components support developing applications on the Grid without taking all the technical details of the particular platform type into account (network communication, heterogeneity, etc.). The GCMenables a hierarchical composition of programpieces and HOCs enable the reuse of component code in the development of new applications by specifying application-specific operations in a program via code parameters. When a programmer is provided, e. g., with a compute farm HOC, only the independent worker tasks must be described. But, once an application exhibits data or control dependences, the trivial farm is no longer sufficient. Here, the power of loop parallelization tools, like LooPo, comes into play: by embedding LooPo into a HOC, we show that these two technologies in combination facilitate the automatic transformation of a sequential loop nest with complex dependences (supplied by the user as a HOC parameter) into an ordered task graph, which can be processed on the Grid in parallel. This technique can significantly simplify GCM-based systems which combine multiple HOCs and other components. We use an equation system solver based on the successive overrelaxation method (SOR) as our motivating application example and for performance experiments.}, language = {en} } @inproceedings{DumitrescuEpemaDuennweber, author = {Dumitrescu, C{\^a}t{\^a}lin L. and Epema, Dick H. J. and D{\"u}nnweber, Jan}, title = {User-Transparent Scheduling for Software Components on the Grid}, series = {Achievements in European Research on Grid Systems}, booktitle = {Achievements in European Research on Grid Systems}, editor = {Gorlatch, Sergei and Bubak, Marian and Priol, Thierry}, publisher = {Springer}, address = {Boston, MA}, isbn = {978-0-387-72811-7}, doi = {10.1007/978-0-387-72812-4_4}, pages = {41 -- 53}, abstract = {Grid applications are increasingly being developed as workflows using well-structured, reusable components. We argue that components with well-defined semantics facilitate an efficient scheduling on the Grid. We have previously developed a user-transparent scheduling approach for Higher-Order Components (HOCs) - parallel implementations of typical programming patterns, accessible and customizable via Web services. Our approach combines three scheduling techniques: using cost functions for reducing communication overhead, reusability of schedules for similar workflows, and the aggregated submission of jobs. We analyze the user-transparent scheduling from four perspectives, namely: the easiness of integration within already existing Grid scheduling systems, the gains for individual users, the resource provider advantages, and the robustness with respect to execution failures. We perform our evaluation using the KOALA Grid scheduler extended to support our user-transparent scheduling, which we run on the DAS-2 system combining over 200 nodes at five sites in the Netherlands. The experimental results show an increase in throughput by more than 100\%, a descreasing of the response time by 50\%, and a failure reduction by 45\% for the considered scenarios}, language = {en} } @article{MuellerIdenDuennweberGorlatchetal., author = {M{\"u}ller-Iden, Jens and D{\"u}nnweber, Jan and Gorlatch, Sergei and Alt, Martin and Fujita, Hamido and Funyu, Yutaka}, title = {Clayworks: Toward user-oriented software for collaborative modeling}, series = {Knowledge-Based Systems}, volume = {22}, journal = {Knowledge-Based Systems}, number = {3}, publisher = {Elsevier}, address = {Oxford, UK}, doi = {10.1016/j.knosys.2008.12.001}, pages = {209 -- 215}, abstract = {We consider the development of software systems that integrate collaborative real-time modeling and distributed computing. Our main goal is user-orientation: we need a collaborative workspace for geographically dispersed users with a seamless access of every user to high-performance servers. This paper presents a particular prototype, Clayworks, that allows modeling of virtual clay objects and running computation-intensive deformation simulations for objects crashing into each other. In order to integrate heterogeneous computational resources, we adopt modern Grid middleware and provide the users with an intuitive graphical interface. Simulations are parallelized using a higher-order component (HOC) which abstracts over the web service resource framework (WSRF) used to interconnect our worksuite to the computation server. Clayworks is a representative of a large class of demanding systems which combine collaborative, user-oriented modeling with performance-critical computations, e.g., crash-tests or simulations of biological population evolution.}, language = {en} } @incollection{DuennweberAldinucciGorlatchetal., author = {D{\"u}nnweber, Jan and Aldinucci, Marco and Gorlatch, Sergei and Campa, Sonia and Danelutto, Marco}, title = {Adaptable Parallel Components for Grid Programming}, series = {Integrated Research in GRID Computing}, booktitle = {Integrated Research in GRID Computing}, editor = {Gorlatch, Sergei and Danelutto, Marco}, publisher = {Springer Verlag}, address = {Boston, MA}, isbn = {978-0-387-47656-8}, doi = {10.1007/978-0-387-47658-2_4}, pages = {43 -- 57}, abstract = {We suggest that parallel software components used for grid computing should be adaptable to application-specific requirements, instead of developing new components from scratch for each particular application. As an example, we take a parallel farm component which is "embarrassingly parallel", i. e., free of dependencies, and adapt it to the wavefront processing pattern with dependencies that impact its behavior. We describe our approach in the context of Higher-Order Components (HOCs), with the Java-based system Lithium as our implementation framework. The adaptation process relies on HOCs' mobile code parameters that are shipped over the network of the grid. We describe our implementation of the proposed component adaptation method and report first experimental results for a particular grid application — the alignment of DNA sequence pairs, a popular, time-critical problem in computational molecular biology.}, language = {en} } @article{DuennweberKirsch, author = {D{\"u}nnweber, Jan and Kirsch, C.}, title = {Report Datenmigration}, series = {iX - Magazin f{\"u}r professionelle Informationstechnik}, journal = {iX - Magazin f{\"u}r professionelle Informationstechnik}, number = {11}, publisher = {Heise}, address = {Hannover}, issn = {0935-9680}, pages = {95 -- 100}, abstract = {Mehrere Terabyte Daten aus einem auf dem Mainframe laufenden COBOL-Programm auf eine SOA-Architektur unter Linux zu migrieren, stellt besondere Anforderungen an die Werkzeuge und Entwickler. Geschickte Kombination vorhandener Tools und effizienter Strategien vermeiden Stillstandszeiten und beschleunigen den Datentransfer.}, language = {de} } @incollection{DuennweberParlavatzasGorlatchetal., author = {D{\"u}nnweber, Jan and Parlavatzas, Nikos and Gorlatch, Sergei and Baude, Francoise and Legrand, Virginie}, title = {Automatic Creation of Web Services for Grid Components}, series = {Integrated Research in GRID Computing}, booktitle = {Integrated Research in GRID Computing}, editor = {Gorlatch, Sergei and Danelutto, Marco}, publisher = {Springer}, address = {Sophia Antipolis, France}, isbn = {978-0-387-47656-8}, doi = {10.1007/978-0-387-47658-2_3}, pages = {31 -- 42}, abstract = {While high-level software components simplify the programming of grid applications and Web services increase their interoperability, developing such components and configuring the interconnecting services is a demanding task. In this paper, we consider the combination of Higher-Order Components (HOCs) with the Fractal component model and the ProActive library. HOCs are parallel programming components, made accessible on the grid via Web services that use a special class loader enabling code mobility: executable code can be uploaded to a HOC, allowing one to customize the HOC. Fractal simplifies the composition of components and the ProActive library offers a generator for automatically creating Web services from components composed with Fractal, as long as all the parameters of these services have primitive types. Taking all the advantages of HOCs, ProActive and Fractal together, the obvious conclusion is that composing HOCs using Fractal and automatically exposing them as Web services on the grid via ProActive minimizes the required efforts for building complex grid systems. In this context, we solved the problem of exchanging code-carrying parameters in automatically generated Web services by integrating the HOC class loading mechanism into the ProActive library.}, language = {en} } @incollection{AldinucciDuennweberDaneluttoetal., author = {Aldinucci, Marco and D{\"u}nnweber, Jan and Danelutto, Marco and Golatch, Sergei}, title = {Optimization techniques for skeletons on grids}, series = {Grid Computing: The New Frontier of High Performance Computing}, booktitle = {Grid Computing: The New Frontier of High Performance Computing}, editor = {Grandinetti, Lucio}, publisher = {Elsevier}, address = {Scotland}, isbn = {978-0-08-046146-5}, doi = {10.1016/S0927-5452(05)80014-0}, pages = {255 -- 273}, abstract = {Skeletons are common patterns of parallelism, such as farm and pipeline, that can be abstracted and offered to the application programmer as programming primitives. We describe the use and implementation of skeletons on emerging computational grids, with the skeleton system Lithium, based on Java and RMI, as our reference programming syttem. Our main contribution is the exploration of optimization techniques for implementing skeletons on grids based on an optimized, future-based RMI mechanism, which we integrate into the macro-dataflow evaluation mechanism of Lithium. We discuss three optimizations: 1) a lookahead mechanism that allows to process multiple tasks concurrently at each grid server and thereby increases the overall degree of parallelism, 2) a lazy taskbinding technique that reduces interactions between grid servers and the task dispatcher, and 3) dynamic improvements that optimize the collecting of results and the work-load balancing. We report experimental results that demonstrate the improvements due to our optimizations on various testbeds, including a heterogeneous grid-like environment.}, language = {en} } @inproceedings{SchraderStadlerDuennweber, author = {Schrader, Jonas and Stadler, Timo and D{\"u}nnweber, Jan}, title = {A Hybrid Genetic Algorithm for Solving the VRP with Pickup and Delivery in Rural Areas}, series = {Proceedings of the 56th Hawaii International Conference on System Sciences: January 3-6, 2023, Maui Hawaii, USA}, booktitle = {Proceedings of the 56th Hawaii International Conference on System Sciences: January 3-6, 2023, Maui Hawaii, USA}, publisher = {University of Hawaiʻi at Mānoa}, address = {Honolulu, HI}, issn = {2572-6862}, pages = {9}, abstract = {In this paper, we present a new Hybrid Genetic Search (HGS) algorithm for solving the Capacitated Vehicle Routing Problem for Pickup and Delivery (CVRPPD) as it is required for public transport in rural areas. One of the biggest peculiarities here is that a large area has to be covered with as few vehicles as possible. The basic idea of this algorithm is based on a more general version of HGS, which we adopted to solve the CVRPPD in rural areas. It also implements improvements that lead to the acceleration of the algorithm and, thereby, to a faster generation of a fastest route. We tested the algorithm on real road data from Roding, a rural district in Bavaria, Germany. Moreover, we designed an API for converting data from the Openrouteservice, so that our algorithm can be applied on real world examples as well.}, language = {en} } @incollection{GorlatchDuennweber, author = {Gorlatch, Sergei and D{\"u}nnweber, Jan}, title = {From Grid Middleware to Grid Applications}, series = {Future Generation Grids}, booktitle = {Future Generation Grids}, editor = {Getov, Vladimir and Laforenza, Domenico and Reinefeld, Alexander}, publisher = {Springer Verlag}, address = {Berlin}, isbn = {978-0-387-27935-0}, doi = {10.1007/978-0-387-29445-2_13}, pages = {241 -- 261}, abstract = {This paper deals with the problem of application programming for grid systems that combine heterogeneous data and computational resources via the Internet. We argue that grid programming is still too complex because of the big gap between the currently used and anticipated grid middleware, (e.g., Globus or WSRF) and the application level. We suggest that this gap needs to be closed in future-generation grids and propose a novel approach to bridging the gap by using Higher-Order Components (HOCs) — recurring patterns of parallel behaviour that are provided to the user as program building blocks with pre-packaged implementation and middleware setup. The presentation is illustrated with a simple case study of computing fractal images. Our experiments demonstrate that HOCs can simplify grid application programming significantly, without serious performance loss.}, language = {en} } @inproceedings{DuennweberGorlatch, author = {D{\"u}nnweber, Jan and Gorlatch, Sergei}, title = {HOC-SA}, series = {IEEE International Conference on Services Computing (SCC 2004), 15-18 Sept. 2004, Shanghai, China}, booktitle = {IEEE International Conference on Services Computing (SCC 2004), 15-18 Sept. 2004, Shanghai, China}, isbn = {0-7695-2225-4}, doi = {10.1109/SCC.2004.1358017}, abstract = {The current efforts on programming grid applications often rely on service-oriented approaches like grid services. This work presents HOC-SA -a service architecture for higher-order components, which provides the programmer with reusable and composable patterns of parallelism and is interoperable with the latest Globus toolkit implementations. We describe our implementation of HOC-SA using OGSA-DAI, a framework for integrating grids with distributed databases. We present a simple example application and report first measurements on our grid testbed.}, language = {en} } @inproceedings{WinkerGroppeUotilaetal., author = {Winker, Tobias and Groppe, Sven and Uotila, Valter Johan Edvard and Yan, Zhengtong and Lu, Jiaheng and Maja, Franz and Mauerer, Wolfgang}, title = {Quantum Machine Learning: Foundation, New Techniques, and Opportunities for Database Research}, series = {SIGMOD '23, proceedings of the 2023 International Conference on Management of Data: June 18-23, 2023, Seattle, WA, USA}, booktitle = {SIGMOD '23, proceedings of the 2023 International Conference on Management of Data: June 18-23, 2023, Seattle, WA, USA}, publisher = {ACM}, address = {New York}, doi = {10.1145/3555041.3589404}, pages = {8}, abstract = {In the last few years, the field of quantum computing has experienced remarkable progress. The prototypes of quantum computers already exist and have been made available to users through cloud services (e.g., IBM Q experience, Google quantum AI, or Xanadu quantum cloud). While fault-tolerant and large-scale quantum computers are not available yet (and may not be for a long time, if ever), the potential of this new technology is undeniable. Quantum algorithms havethe proven ability to either outperform classical approaches for several tasks, or are impossible to be efficiently simulated by classical means under reasonable complexity-theoretic assumptions. Even imperfect current-day technology is speculated to exhibit computational advantages over classical systems. Recent research is using quantum computers to solve machine learning tasks. Meanwhile, the database community already successfully applied various machine learning algorithms for data management tasks, so combining the fields seems to be a promising endeavour. However, quantum machine learning is a new research field for most database researchers. In this tutorial, we provide a fundamental introduction to quantum computing and quantum machine learning and show the potential benefits and applications for database research. In addition, we demonstrate how to apply quantum machine learning to the optimization of join order problem for databases.}, language = {en} } @article{HerrmannKirschnerKleinertetal., author = {Herrmann, Frank and Kirschner, Jan Michael and Kleinert, Thomas and Fritzsche, Harald}, title = {Big Data im Bereich der technischen Sauberkeit}, series = {Anwendungen und Konzepte der Wirtschaftsinformatik (AKWI)}, journal = {Anwendungen und Konzepte der Wirtschaftsinformatik (AKWI)}, number = {13}, publisher = {Hochschule}, address = {Luzern}, issn = {2296-4592}, doi = {10.26034/lu.akwi.2021.3296}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-30550}, pages = {34 -- 42}, abstract = {Dieses Projekt befasst sich mit Fragestellungen zur Anwendung von k{\"u}nstlicher Intelligenz im Bereich der Technischen Sauberkeit. Durch Literaturforschungen, die einen Ablauf nach Fettke 2006 haben, werden KI-Anwendungen gesucht, die bereits im Zusammenhang mit der Technischen Sauberkeit verwendet werden. Die Forschungen konnten zw{\"o}lf Literaturquellen ermitteln. Durch diese Literaturanalyse wurde festgestellt, dass 91 Prozent CV (Computer Vision) zur Partikelerkennung verwenden. Aus diesem Grund wurde anschließend ein CV Modell zur Partikelerkennung implementiert. Durch die Konfusionsmatrix konnte eine Treffergenauigkeit von 82 Prozent festgestellt werden. Daraus folgt, dass eine Partikelklassifikation m{\"o}glich ist. Abschließend wurde eine weitere Literaturforschung zu Text Mining Applikationen durchgef{\"u}hrt, da der Bereich der Qualit{\"a}tsanalyse im Monitoring laut Aufgabenstellung eingezogen werden sollte. In dieser konnte kein positives Ergebnis erzielt werden, da speziell nach fertigen Anwendungen gesucht wurde, die Analysetexte im Bereich der technischen Sauberkeit kategorisieren k{\"o}nnen.}, language = {de} } @incollection{FrikelHaltmeier, author = {Frikel, J{\"u}rgen and Haltmeier, Markus}, title = {Sparse Regularization of Inverse Problems by Operator-Adapted Frame Thresholding}, series = {Mathematics of Wave Phenomena}, booktitle = {Mathematics of Wave Phenomena}, editor = {D{\"o}rfler, Willy and Hochbruck, Marlis and Hundertmark, Dirk and Reichel, Wolfgang and Rieder, Andreas}, edition = {1st ed.}, publisher = {Birkh{\"a}user; Springer International Publishing}, address = {Cham}, isbn = {978-3-030-47173-6}, doi = {10.1007/978-3-030-47174-3_10}, pages = {163 -- 178}, abstract = {We analyze sparse frame based regularization of inverse problems by means of a diagonal frame decomposition (DFD) for the forward operator, which generalizes the SVD. The DFD allows to define a non-iterative (direct) operator-adapted frame thresholding approach which we show to provide a convergent regularization method with linear convergence rates. These results will be compared to the well-known analysis and synthesis variants of sparse ℓ1-regularization which are usually implemented thorough iterative schemes. If the frame is a basis (non-redundant case), the three versions of sparse regularization, namely synthesis and analysis variants of ℓ1-regularization as well as the DFD thresholding are equivalent. However, in the redundant case, those three approaches are pairwise different.}, language = {en} } @inproceedings{WindbuehlerOkkesimChristetal., author = {Windb{\"u}hler, Anna and Okkesim, S{\"u}kr{\"u} and Christ, Olaf and Mottaghi, Soheil and Rastogi, Shavika and Schmuker, Michael and Baumann, Timo and Hofmann, Ulrich G.}, title = {Machine Learning Approaches to Classify Anatomical Regions in Rodent Brain from High Density Recordings}, series = {44th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC 2022): 11-15 July 2022, Glasgow, Scotland, United Kingdom}, booktitle = {44th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC 2022): 11-15 July 2022, Glasgow, Scotland, United Kingdom}, publisher = {IEEE}, doi = {10.1109/EMBC48229.2022.9871702}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-35296}, pages = {3530 -- 3533}, abstract = {Identifying different functional regions during a brain surgery is a challenging task usually performed by highly specialized neurophysiologists. Progress in this field may be used to improve in situ brain navigation and will serve as an important building block to minimize the number of animals in preclinical brain research required by properly positioning implants intraoperatively. The study at hand aims to correlate recorded extracellular signals with the volume of origin by deep learning methods. Our work establishes connections between the position in the brain and recorded high-density neural signals. This was achieved by evaluating the performance of BLSTM, BGRU, QRNN and CNN neural network architectures on multisite electrophysiological data sets. All networks were able to successfully distinguish cortical and thalamic brain regions according to their respective neural signals. The BGRU provides the best results with an accuracy of 88.6 \% and demonstrates that this classification task might be solved in higher detail while minimizing complex preprocessing steps.}, language = {en} } @inproceedings{SahaNayakBaumann, author = {Saha, Debjoy and Nayak, Shravan and Baumann, Timo}, title = {Merkel Podcast Corpus: A Multimodal Dataset Compiled from 16 Years of Angela Merkel's Weekly Video Podcasts}, series = {Proceedings of the 13th Conference on Language Resources and Evaluation (LREC 2022), Marseille, 20-25 June 2022}, booktitle = {Proceedings of the 13th Conference on Language Resources and Evaluation (LREC 2022), Marseille, 20-25 June 2022}, organization = {European Language Resources Association (ELRA)}, pages = {2536 -- 2540}, abstract = {We introduce the Merkel Podcast Corpus, an audio-visual-text corpus in German collected from 16 years of (almost) weekly Internet podcasts of former German chancellor Angela Merkel. To the best of our knowledge, this is the first single speaker corpus in the German language consisting of audio, visual and text modalities of comparable size and temporal extent. We describe the methods used with which we have collected and edited the data which involves downloading the videos, transcripts and other metadata, forced alignment, performing active speaker recognition and face detection to finally curate the single speaker dataset consisting of utterances spoken by Angela Merkel. The proposed pipeline is general and can be used to curate other datasets of similar nature, such as talk show contents. Through various statistical analyses and applications of the dataset in talking face generation and TTS, we show the utility of the dataset. We argue that it is a valuable contribution to the research community, in particular, due to its realistic and challenging material at the boundary between prepared and spontaneous speech. Accepted at LREC 2022}, language = {en} } @inproceedings{WinterspergerSafiMauerer, author = {Wintersperger, Karen and Safi, Hila and Mauerer, Wolfgang}, title = {QPU-System Co-Design for Quantum HPC Accelerators?}, series = {Architecture of Computing Systems: 35th International Conference, ARCS 2022, Heilbronn, Germany, September 13-15, 2022, Proceedings}, booktitle = {Architecture of Computing Systems: 35th International Conference, ARCS 2022, Heilbronn, Germany, September 13-15, 2022, Proceedings}, publisher = {Springer}, isbn = {978-3-031-21866-8}, doi = {10.1007/978-3-031-21867-5_7}, pages = {100 -- 114}, abstract = {The use of quantum processing units (QPUs) promises speed-ups for solving computational problems, but the quantum devices currently available possess only a very limited number of qubits and suffer from considerable imperfections. One possibility to progress towards practical utility is to use a co-design approach: Problem formulation and algorithm, but also the physical QPU properties are tailored to the specific application. Since QPUs will likely be used as accelerators for classical computers, details of systemic integration into existing architectures are another lever to influence and improve the practical utility of QPUs. In this work, we investigate the influence of different parameters on the runtime of quantum programs on tailored hybrid CPU-QPU-systems. We study the influence of communication times between CPU and QPU, how adapting QPU designs influences quantum and overall execution performance, and how these factors interact. Using a simple model that allows for estimating which design choices should be subjected to optimisation for a given task, we provide an intuition to the HPC community on potentials and limitations of co-design approaches. We also discuss physical limitations for implementing the proposed changes on real quantum hardware devices.}, language = {en} } @article{DavendraHerrmannBialicDavendra, author = {Davendra, Donald and Herrmann, Frank and Bialic-Davendra, Magdalena}, title = {Chaotic Flower Pollination Algorithm for scheduling tardiness-constrained flow shop with simultaneously loaded stations}, series = {Neural computing \& applications}, journal = {Neural computing \& applications}, publisher = {Springer Nature}, doi = {10.1007/s00521-022-08044-0}, abstract = {This paper introduces a novel chaotic flower pollination algorithm (CFPA) to solve a tardiness-constrained flow-shop scheduling problem with simultaneously loaded stations. This industrial manufacturing problem is modeled from a filter basket production line in Germany and has been generally solved using standard deterministic algorithms. This research develops a metaheuristic approach based on the highly efficient flower pollination algorithm coupled with different chaos maps for stochasticity. The objective function targeted is the tardiness constraint of the due dates. Fifteen different experiments with thirty scenarios are generated to mimic industrial conditions. The results are compared with the genetic algorithm and with the four standard benchmark priority rule-based deterministic algorithms of First In First Out, Raghu and Rajendran, Shortest Processing Time and Slack. From the obtained results and analysis of the relative difference, percentage relative difference and t tests, CFPA was found to be significantly better performing than the deterministic heuristics and the GA algorithm.}, language = {en} } @book{Mauerer, author = {Mauerer, Wolfgang}, title = {Linux-Kernelarchitektur : Konzepte Strukturen und Algorithmen von Kernel 2.6}, publisher = {Hanser}, address = {M{\"u}nchen}, isbn = {9783446225664}, language = {de} } @phdthesis{Frikel, author = {Frikel, J{\"u}rgen}, title = {Reconstructions in limited angle x-ray tomography: Characterization of classical reconstructions and adapted curvelet sparse regularization}, publisher = {Technische Universit{\"a}t M{\"u}nchen}, address = {M{\"u}nchen}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:91-diss-20130328-1115037-0-3}, abstract = {This thesis is devoted to the problem of tomographic reconstruction at limited angular range. In the first part, we prove a characterization of filtered backprojection reconstructions from limited angle data. Moreover, we develop a strategy for artifact reduction and stabilization. In the second part, we introduce a new edge-preserving reconstruction algorithm for limited angle tomography and analyze this algorithm mathematically. Some numerical experiments are also presented.}, language = {en} } @inproceedings{Raptis, author = {Raptis, Georgios}, title = {Die Konzepte und Mechanismen der elektronischen Gesundheitskarte und des Heilberufsausweises aus der Sicht der Datensicherheit / des Datenschutzes}, series = {Forschungsseminar med. Informatik an der Universit{\"a}t Heidelberg, 22.06.2006}, booktitle = {Forschungsseminar med. Informatik an der Universit{\"a}t Heidelberg, 22.06.2006}, subject = {Elektronische Gesundheitskarte}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {{\"U}bersicht {\"u}ber die neuen Technischen Richtlinien des BSI zum ersetzenden Scannen und zur Langzeitarchivierung}, series = {Telemed 2014, Berlin, 14.10.2014}, journal = {Telemed 2014, Berlin, 14.10.2014}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Mobile Szenarien f{\"u}r Anwendungen der eGK}, series = {CAST-Workshop Smartcards, Darmstadt, 25.09.2014}, journal = {CAST-Workshop Smartcards, Darmstadt, 25.09.2014}, subject = {Elektronische Gesundheitskarte}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Datenschutzfragen zur Telemedizin}, series = {Fachtagung Datenschutz in der Medizin - Update 2015 I, Hamburg 03.02.2015}, journal = {Fachtagung Datenschutz in der Medizin - Update 2015 I, Hamburg 03.02.2015}, subject = {Telemedizin}, language = {de} } @inproceedings{Raptis, author = {Raptis, Georgios}, title = {Ein Verfahren zur L{\"o}sung des Problems der kryptographischen Langzeitsicherheit medizinischer Daten, die in einer Infrastruktur gespeichert werden}, series = {BIOSIG-Konferenz 2007, Darmstadt}, booktitle = {BIOSIG-Konferenz 2007, Darmstadt}, abstract = {Medizinische Daten, die - wie derzeit f{\"u}r die Telematik-Infrastruktur nach \S291a SGB V spe-zifiziert - auch außerhalb der physischen Kontrolle der Eigent{\"u}mer oder Ersteller (also z.B. außerhalb von Arztpraxen oder Klinken) auf Servern kryptographisch verschl{\"u}sselt gespeichert werden, m{\"u}ssen sehr lange vertraulich bleiben. Insbesondere darf der technische Betreiber des Servers, der die Daten speichert, keinen Zugriff erlangen. Es kann jedoch keine verl{\"a}ssliche Aussage dahingehend getroffen werden, ob die heute eingesetzten kryp-tographischen Algorithmen in 30 oder 40 Jahren die Vertraulichkeit der medizinischen Daten weiterhin gew{\"a}hrleisten. Es wird ein Verfahren vorgestellt, welches das Problem der langfristigen Sicherheit von verschl{\"u}sselt gespeicherten medizinischen Daten aus kryptographischer Sicht l{\"o}st. Die Anwendung des Verfahrens wird am Beispiel einer nach den derzeit bekannten gematik-Spezifikationen definierten Infrastruktur veranschaulicht. Es wird von einer getrennten Speicherung von verschl{\"u}sselten medizinischen Daten und Schl{\"u}sselmaterial ausgegangen. Die Daten werden an der Datenquelle (Konnektor, z.B. eines Arztes) mit einem Einmalblock (One Time Pad, OTP) verschl{\"u}sselt. Sie sind damit beweisbar sicher verschl{\"u}sselt, weil das One-Time-Pad-Verschl{\"u}sselungsverfahren beweisbar „perfekt geheim" ist. Der OTP-Schl{\"u}ssel wird mit einem symmetrischen Schl{\"u}ssel verschl{\"u}sselt, der wiederum mit den asymmetrischen Schl{\"u}sseln aller Zugriffsberechtigten verschl{\"u}sselt wird. Die kryptographische, technische und organisatorische Sicherheit des Verfahrens sowie seine Voraussetzungen und Kosten werden analysiert.}, subject = {Gesundheitsinformationssystem}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Biometrie - Anwendungen und Datenschutz. Welche Zusatzinformationen liefert der IRIS-Pf{\"o}rtner? Nebennutzen in einem biometrischen Zugangskontrollsystem. Medizinische Hintergr{\"u}nde. Symposium des Bundesamtes f{\"u}r Sicherheit in der Informationstechnik, Vortrag, Darmstadt 23. Mai 2002}, series = {Symposium des Bundesamtes f{\"u}r Sicherheit in der Informationstechnik}, journal = {Symposium des Bundesamtes f{\"u}r Sicherheit in der Informationstechnik}, language = {de} } @article{BuschDaumRaptis, author = {Busch, Ch. and Daum, H. and Raptis, Georgios}, title = {Merkmal Iris. K{\"o}nnen diese Augen l{\"u}gen?}, series = {Spektrum der Wissenschaft}, journal = {Spektrum der Wissenschaft}, number = {7}, pages = {81 -- 82}, subject = {Biometrie}, language = {de} } @book{SauerWolfBuchetal., author = {Sauer, S. and Wolf, Th. and Buch, M. and Raptis, Georgios}, title = {Sichere Client-Server-Architekturen f{\"u}r E-Government}, pages = {192}, subject = {Client-Server-Konzept}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {M{\"o}gliche Auswirkungen der eIDAS-Verordnung auf die Telematikinfrastruktur und die eArztausweise}, series = {CAST-Workshop PKI, Darmstadt, 29.01.2015}, journal = {CAST-Workshop PKI, Darmstadt, 29.01.2015}, subject = {Europ{\"a}ische Union }, language = {de} } @masterthesis{Raptis, type = {Bachelor Thesis}, author = {Raptis, Georgios}, title = {Klassifikation, Anwendungen und Sicherheitskonzept von Trustcentern}, subject = {Trust Center}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Ist die Sicherheit der medizinischen Daten in der Telematik-Infrastruktur zu gew{\"a}hrleisten?}, series = {Kolloquium Wissenschaftlichkeit in der Medizin, Universit{\"a}t Heidelberg, 10.05.2007}, journal = {Kolloquium Wissenschaftlichkeit in der Medizin, Universit{\"a}t Heidelberg, 10.05.2007}, subject = {Telemedizin}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Datenschutz und IT-Sicherheit: Empfehlungen von B{\"A}K und KBV f{\"u}r {\"A}rzte}, series = {AK-Sicherheit des eco-Verband der deutschen Internetwirtschaft e.V., K{\"o}ln, 06.05.2009}, journal = {AK-Sicherheit des eco-Verband der deutschen Internetwirtschaft e.V., K{\"o}ln, 06.05.2009}, subject = {Arztpraxis}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Sichere Gesundheitsdaten in der Cloud? Technische Voraussetzungen und Regelungen}, series = {8. Rhein-Main Zukunftskongress Krankenhaus \& Partner 2014, Offenbach, 21.2.2014}, journal = {8. Rhein-Main Zukunftskongress Krankenhaus \& Partner 2014, Offenbach, 21.2.2014}, subject = {Cloud Computing}, language = {de} } @article{Raptis, author = {Raptis, Georgios}, title = {App statt Arzt ist kein gutes Motto}, series = {medizin \& technik}, journal = {medizin \& technik}, number = {2}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Papierlose Praxis \& Digitalisierung}, series = {6. BMVZ-Praktikerkongress des Bundesverbands Medizinische Versorgungszentren - Gesundheitszentren - Integrierte Versorgung e.V, 12.09.2012 Berlin, zertifiziert von der {\"A}rztekammer Berlin}, journal = {6. BMVZ-Praktikerkongress des Bundesverbands Medizinische Versorgungszentren - Gesundheitszentren - Integrierte Versorgung e.V, 12.09.2012 Berlin, zertifiziert von der {\"A}rztekammer Berlin}, subject = {Arztpraxis}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Die elektronische Gesundheitskarte}, series = {7. Kommunikationsforum "Industry meets Medicine", Olpe, 5.11.2014}, journal = {7. Kommunikationsforum "Industry meets Medicine", Olpe, 5.11.2014}, subject = {Elektronische Gesundheitskarte}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {HPCs als Basis f{\"u}r den elektronischen Arztausweis}, series = {Smartcard-Workshops, Fraunhofer SIT, 07.02.2006}, journal = {Smartcard-Workshops, Fraunhofer SIT, 07.02.2006}, subject = {Arzt}, language = {de} } @misc{Raptis, author = {Raptis, Georgios}, title = {Vernetzung und ubiquit{\"a}re Informationsverarbeitung - technisch-organisatorischer Datenschutz in der Arztpraxis}, series = {2. Fachtagung der Gesellschaft f{\"u}r Datenschutz und Datensicherheit e.V. (GDD), Berlin, 13.05.2014, zertifiziert von der {\"A}rztekammer Berlin}, journal = {2. Fachtagung der Gesellschaft f{\"u}r Datenschutz und Datensicherheit e.V. (GDD), Berlin, 13.05.2014, zertifiziert von der {\"A}rztekammer Berlin}, subject = {Arztpraxis}, language = {de} } @phdthesis{Raptis, author = {Raptis, Georgios}, title = {Vertraulichkeit von medizinischen Daten in der Telematik-Infrastruktur - Sicherheitsanalyse unter Ber{\"u}cksichtigung von Aspekten der langfristigen Sicherheit}, address = {Heidelberg}, subject = {Medizinische Dokumentation}, language = {de} } @inproceedings{LierMartinekStammingeretal., author = {Lier, Alexander and Martinek, Magdalena and Stamminger, Marc and Selgrad, Kai}, title = {A High-Resolution Compression Scheme for Ray Tracing Subdivision Surfaces with Displacement}, series = {Proceedings of the ACM on Computer Graphics and Interactive Techniques}, volume = {1}, booktitle = {Proceedings of the ACM on Computer Graphics and Interactive Techniques}, number = {2}, publisher = {The Association for Computers in Mathematics and Science Teaching}, doi = {10.1145/3233308}, pages = {1 -- 17}, abstract = {Subdivision surfaces, especially with displacement, are one of the key modeling primitives used in high-quality rendering environments, such as, e.g., movie production. While their use easily maps to rasterization-based frameworks, they pose a significant challenge for ray tracing environments. This is due to the fact that incoherent access patterns require storing or caching fully tessellated and displaced meshes for efficient intersection computations. In this paper we use a two-tier hierarchy built on a scene's patches. It relies on compressed and quantized bounding volumes on the second tier to reduce the size of the BVH itself. Based on this acceleration structure, we propose a quantized, compact approximation for leaf nodes while being faithful to the underlying patch-geometry. We build on recent advances and present a system that shows competitive performance regarding run-time speed, which is close to full-resolution pre-tessellation methods as well as to previous compression approaches. Ultimately, we provide strong compression of up to a factor of 5: 1 compared to state-of-the-art methods while maintaining high geometrical fidelity surpassing similarly compact approximations and getting close to uncompressed geometry.}, language = {en} } @inproceedings{Raptis, author = {Raptis, Georgios}, title = {Empfehlungen der B{\"A}K zum Datenschutz im Praxisalltag, Darstellung unter technischen Aspekten}, series = {conhIT 2009, Berlin, 22.04.2009}, booktitle = {conhIT 2009, Berlin, 22.04.2009}, subject = {Arztpraxis}, language = {de} } @unpublished{FrikelQuinto, author = {Frikel, J{\"u}rgen and Quinto, Eric Todd}, title = {A paradigm for the characterization of artifacts in tomography}, doi = {10.48550/arXiv.1409.4103}, abstract = {We present a paradigm for characterization of artifacts in limited data tomography problems. In particular, we use this paradigm to characterize artifacts that are generated in reconstructions from limited angle data with generalized Radon transforms and general filtered backprojection type operators. In order to find when visible singularities are imaged, we calculate the symbol of our reconstruction operator as a pseudodifferential operator.}, language = {en} } @inproceedings{LierStammingerSelgrad, author = {Lier, Alexander and Stamminger, Marc and Selgrad, Kai}, title = {CPU-Style SIMD Ray Traversal on GPUs}, series = {Proceedings of the Conference on High-Performance Graphics}, booktitle = {Proceedings of the Conference on High-Performance Graphics}, publisher = {Association for Computing Machinery}, address = {New York, NY, USA}, isbn = {9781450358965}, doi = {10.1145/3231578.3231583}, pages = {1 -- 4}, abstract = {In this paper we describe and evaluate an implementation of CPU-style SIMD ray traversal on the GPU. We show how spreading moderately wide BVHs (up to a branching factor of eight) across multiple threads in a warp can improve performance while not requiring expensive pre-processing. The presented ray-traversal method exhibits improved traversal performance especially for increasingly incoherent rays.}, language = {en} } @inproceedings{SelgradMuellerReintgesetal., author = {Selgrad, Kai and M{\"u}ller, Jonas and Reintges, Christian and Stamminger, Marc}, title = {Fast Shadow Map Rendering for Many-Lights Settings}, series = {Eurographics Symposium on Rendering - Experimental Ideas \& Implementations}, booktitle = {Eurographics Symposium on Rendering - Experimental Ideas \& Implementations}, editor = {Eisemann, Elmar and Fiume, Eugene}, publisher = {The Eurographics Association}, isbn = {978-3-03868-019-2}, doi = {10.2312/sre.20161208}, pages = {41 -- 48}, abstract = {n this paper we present a method to efficiently cull large parts of a scene prior to shadow map computations for many-lights settings. Our method is agnostic to how the light sources are generated and thus works with any method of light distribution. Our approach is based on previous work in culling for ray traversal to speed up area light sampling. Applied to shadow mapping our method works for high- and low-resolution shadow maps and, in contrast to previous work on many-lights rendering, does neither entail scene approximations nor imposes limits on light range, while still providing significant gains in performance. In contrast to standard culling methods shadow map rendering itself is sped up by a factor of 1.5 to 8.6 while the speedup of shadow map rendering, lookup and shading together ranges from 1.1 to 4.2}, language = {en} } @article{Weber, author = {Weber, Karsten}, title = {Terahertzscanner}, series = {EMF Monitor - Elektromagnetische Felder, Umwelt und Gesundheit}, volume = {14}, journal = {EMF Monitor - Elektromagnetische Felder, Umwelt und Gesundheit}, number = {3}, language = {de} } @article{Weber, author = {Weber, Karsten}, title = {The Next Step: Privacy Invasions by Biometrics and ICT Implants}, series = {Ubiquity. An ACM IT Magazine and Forum}, volume = {7}, journal = {Ubiquity. An ACM IT Magazine and Forum}, number = {45}, doi = {10.1145/1195937.1187567}, language = {en} } @incollection{Weber, author = {Weber, Karsten}, title = {Closing the Digital Divide - lokal, nicht global}, series = {Technology Assessment in der Weltgesellschaft}, booktitle = {Technology Assessment in der Weltgesellschaft}, editor = {Bora, A. and Br{\"o}chler, S. and Decker, Michael}, publisher = {Edition Sigma}, address = {Berlin}, pages = {177 -- 190}, language = {de} } @incollection{Weber, author = {Weber, Karsten}, title = {New Mobile Devices and Surveillance: Questions Concerning Epistemology and Some New Challenges for Privacy and Data Protection}, series = {Postmodern Quests in Applied Philosophy}, booktitle = {Postmodern Quests in Applied Philosophy}, editor = {Kolb, David and Salman, Ahmed Shaikh and Druzin, Bryan}, publisher = {Editura Lumen}, address = {Iasi}, language = {en} } @incollection{WeberDrueekeSchulz, author = {Weber, Karsten and Dr{\"u}eke, Ricarda and Schulz, Axel}, title = {Mobile ICT in public spaces and its impact on privacy}, series = {Societies and Cities in the Age of Instant Access}, volume = {88}, booktitle = {Societies and Cities in the Age of Instant Access}, editor = {Miller, Harvey J.}, publisher = {Springer}, address = {Berlin}, doi = {10.1007/1-4020-5427-0_13}, pages = {197 -- 208}, language = {en} } @inproceedings{WeberDrueeke, author = {Weber, Karsten and Dr{\"u}eke, Ricarda}, title = {Privacy, personal data protection, and the need to differentiate}, series = {Ethics of New Information Technology. Proceedings of the 6th International Conference of Computer Ethics: Philosophical Enquiries (CEPE2005)}, booktitle = {Ethics of New Information Technology. Proceedings of the 6th International Conference of Computer Ethics: Philosophical Enquiries (CEPE2005)}, editor = {Brey, Philip and Grodzinsky, F. and Introna, L.}, pages = {13}, abstract = {The coming years will be characterized by the development of mobile ICT that will enable con - sumers to use information and communication services everywhere and anytime. Technologies like GPRS, WLAN, or UMTS can be used stand-alone or in combination with other technologies like RFID or GPS to provide, for instance, location-aware services. Mobile ICT is to be expected to evolve to that what often is called Ambient Intelligence, Ubiquitous or Pervasive Computing. It is likely that such new technologies will affect personnel privacy because providing mobile ICT services inherits the identification and often the exact localization of users. In the following text we shall analyze possible threats of privacy. We will distinguish different dimensions or aspects of privacy to show how new technologies can affect them. After that, we shall argue that it is necessary to make a distinction of privacy and data protection: privacy primarily is a matter of social norms and data protection the realm of technical measurements. Additionally, we will provide some empirical evidence that users of the Internet make that distinction. Finally, we will claim that the right to privacy and privacy itself only can be protected if there are widely accepted social norms regarding privacy.}, language = {en} } @incollection{WeberDrueekeSchulz, author = {Weber, Karsten and Dr{\"u}eke, Ricarda and Schulz, Axel}, title = {Mobiler Wissenszugang: Digital Rights Management vs. Privacy}, series = {Wissensorganisation und Verantwortung. Gesellschaftliche, {\"o}konomische und technische Aspekte}, booktitle = {Wissensorganisation und Verantwortung. Gesellschaftliche, {\"o}konomische und technische Aspekte}, editor = {Ohly, Heinz Peter and Sieglerschmidt, J. and Swertz, C.}, publisher = {Ergon}, address = {W{\"u}rzburg}, pages = {180 -- 193}, language = {de} } @article{GoldhackerTomeGreenleeetal., author = {Goldhacker, Markus and Tom{\´e}, Ana Maria and Greenlee, Mark W. and Lang, Elmar Wolfgang}, title = {Frequency-Resolved Dynamic Functional Connectivity Reveals Scale-Stable Features of Connectivity-States}, series = {Frontiers in Human Neuroscience}, volume = {12}, journal = {Frontiers in Human Neuroscience}, publisher = {Frontiers Research Foundation}, address = {Lausanne}, issn = {1662-5161}, doi = {10.3389/fnhum.2018.00253}, pages = {1 -- 16}, abstract = {Investigating temporal variability of functional connectivity is an emerging field in connectomics. Entering dynamic functional connectivity by applying sliding window techniques on resting-state fMRI (rs-fMRI) time courses emerged from this topic. We introduce frequency-resolved dynamic functional connectivity (frdFC) by means of multivariate empirical mode decomposition (MEMD) followed up by filter-bank investigations. In general, we find that MEMD is capable of generating time courses to perform frdFC and we discover that the structure of connectivity-states is robust over frequency scales and even becomes more evident with decreasing frequency. This scale-stability varies with the number of extracted clusters when applying k-means. We find a scale-stability drop-off from k = 4 to k = 5 extracted connectivity-states, which is corroborated by null-models, simulations, theoretical considerations, filter-banks, and scale-adjusted windows. Our filter-bank studies show that filter design is more delicate in the rs-fMRI than in the simulated case. Besides offering a baseline for further frdFC research, we suggest and demonstrate the use of scale-stability as a possible quality criterion for connectivity-state and model selection. We present first evidence showing that connectivity-states are both a multivariate, and a multiscale phenomenon. A data repository of our frequency-resolved time-series is provided.}, language = {en} } @inproceedings{LierFrankeStammingeretal., author = {Lier, Alexander and Franke, Linus and Stamminger, Marc and Selgrad, Kai}, title = {A Case Study in Implementation-Space Exploration}, series = {Proceedings of the 9th European Lisp Symposium (ELS 2016) ; AGH University of Science and Technology, Krak{\´o}w, Poland, May 9 - 10, 2016}, booktitle = {Proceedings of the 9th European Lisp Symposium (ELS 2016) ; AGH University of Science and Technology, Krak{\´o}w, Poland, May 9 - 10, 2016}, editor = {Durand, Ir{\`e}ne}, publisher = {ACM}, address = {New York, NY, USA}, isbn = {978-2-9557474-0-7}, pages = {83 -- 90}, abstract = {In this paper we show how a feature-oriented development methodology can be exploited to investigate a large set of possible implementations for a real-time rendering algorithm. We rely on previously published work to explore potential dimensions of the implementation space of an algorithm to be run on a graphics processing unit (GPU) using CUDA. The main contribution of our paper is to provide a clear example of the benefit to be gained from existing methods in a domain that only slowly moves toward higher level abstractions. Our method employs a generative approach and makes heavy use of Common Lisp-macros before the code is ultimately transformed to CUDA.}, language = {en} } @inproceedings{SelgradLierKoeferletal., author = {Selgrad, Kai and Lier, Alexander and K{\"o}ferl, Franz and Stamminger, Marc and Lohmann, Daniel}, title = {Lightweight, Generative Variant Exploration for High-performance Graphics Applications}, series = {GPCE'15 : Proceedings of the 2015 ACM SIGPLAN International Conference on Generative Programming: Concepts and Experiences ; October 26-27, 2015, Pittsburgh, PA, USA}, booktitle = {GPCE'15 : Proceedings of the 2015 ACM SIGPLAN International Conference on Generative Programming: Concepts and Experiences ; October 26-27, 2015, Pittsburgh, PA, USA}, editor = {K{\"a}stner, Christian and Gokhāl{\´e}, Anir{\"u}ddhā}, publisher = {ACM}, address = {New York, USA}, isbn = {978-1-4503-3687-1}, pages = {141 -- 150}, abstract = {Rendering performance is an everlasting goal of computer graphics and significant driver for advances in both, hardware architecture and algorithms. Thereby, it has become possible to apply advanced computer graphics technology even in low-cost embedded appliances, such as car instruments. Yet, to come up with an efficient implementation, developers have to put enormous efforts into hardware/problem-specific tailoring, fine-tuning, and domain exploration, which requires profound expert knowledge. If a good solution has been found, there is a high probability that it does not work as well with other architectures or even the next hardware generation. Generative DSL-based approaches could mitigate these efforts and provide for an efficient exploration of algorithmic variants and hardware-specific tuning ideas. However, in vertically organized industries, such as automotive, suppliers are reluctant to introduce these techniques as they fear loss of control, high introduction costs, and additional constraints imposed by the OEM with respect to software and tool-chain certification. Moreover, suppliers do not want to share their generic solutions with the OEM, but only concrete instances. To this end, we propose a light-weight and incremental approach for meta programming of graphics applications. Our approach relies on an existing formulation of C-like languages that is amenable to meta programming, which we extend to become a lightweight language to combine algorithmic features. Our method provides a concise notation for meta programs and generates easily sharable output in the appropriate C-style target language.}, language = {en} } @inproceedings{BenthinWoopNiessneretal., author = {Benthin, Carsten and Woop, Sven and Niessner, Matthias and Selgrad, Kai and Wald, Ingo}, title = {Efficient Ray Tracing of Subdivision Surfaces Using Tessellation Caching}, series = {Proceedings of the 7th Conference on High-Performance Graphics (HPG '15)}, booktitle = {Proceedings of the 7th Conference on High-Performance Graphics (HPG '15)}, publisher = {ACM}, address = {New York, NY, USA - via ACM DL}, isbn = {978-1-4503-3707-6}, doi = {10.1145/2790060.2790061}, pages = {5 -- 12}, abstract = {A common way to ray trace subdivision surfaces is by constructing and traversing spatial hierarchies on top of tessellated input primitives. Unfortunately, tessellating surfaces requires a substantial amount of memory storage, and involves significant construction and memory I/O costs. In this paper, we propose a lazy-build caching scheme to efficiently handle these problems while also exploiting the capabilities of today's many-core architectures. To this end, we lazily tessellate patches only when necessary, and utilize adaptive subdivision to efficiently evaluate the underlying surface representation. The core idea of our approach is a shared lazy evaluation cache, which triggers and maintains the surface tessellation. We combine our caching scheme with SIMD-optimized subdivision primitive evaluation and fast hierarchy construction over the tessellated surface. This allows us to achieve high ray tracing performance in complex scenes, outperforming the state of the art while requiring only a fraction of the memory. In addition, our method stays within a fixed memory budget regardless of the tessellation level, which is essential for many applications such as movie production rendering. Beyond the results of this paper, we have integrated our method into Embree, an open source ray tracing framework, thus making interactive ray tracing of subdivision surfaces publicly available.}, language = {en} } @inproceedings{SelgradLierDoerntleinetal., author = {Selgrad, Kai and Lier, Alexander and D{\"o}rntlein, Jan and Reiche, Oliver and Stamminger, Marc}, title = {A High-Performance Image Processing DSL for Heterogeneous Architectures}, series = {Proceedings of the 9th European Lisp Symposium (ELS 2016), Krakow, Poland}, booktitle = {Proceedings of the 9th European Lisp Symposium (ELS 2016), Krakow, Poland}, editor = {Durand, Ir{\`e}ne}, publisher = {ACM}, address = {New York, NY, USA}, isbn = {978-2-9557474-0-7}, pages = {39 -- 46}, abstract = {Over the last decade a number of high performance, domain-specific languages (DSLs) have started to grow and help tackle the problem of ever diversifying hard- and software employed in fields such as HPC (high performance computing), medical imaging, computer vision etc. Most of those approaches rely on frameworks such as LLVM for efficient code generation and, to reach a broader audience, take input in C-like form. In this paper we present a DSL for image processing that is on-par with competing methods, yet its design principles are in strong contrast to previous approaches. Our tool chain is much simpler, easing the burden on implementors and maintainers, while our output, C-family code, is both adaptable and shows high performance. We believe that our methodology provides a faster evaluation of language features and abstractions in the domains above.}, language = {en} } @inproceedings{HofmannBogendoerferStammingeretal., author = {Hofmann, Nikolai and Bogend{\"o}rfer, Phillip and Stamminger, Marc and Selgrad, Kai}, title = {Hierarchical Multi-layer Screen-space Ray Tracing}, series = {Proceedings of High Performance Graphics (HPG '17), July 28 - 30, 2017, Los Angeles California}, booktitle = {Proceedings of High Performance Graphics (HPG '17), July 28 - 30, 2017, Los Angeles California}, publisher = {ACM}, address = {New York, NY, USA}, isbn = {978-1-4503-5101-0}, doi = {10.1145/3105762.3105781}, pages = {1 -- 10}, abstract = {In this paper we present a method for fast screen-space ray tracing. Single-layer screen-space ray marching is an established tool in high-performance applications, such as games, where plausible and appealing results are more important than strictly correct ones. However, even in such tightly controlled environments, missing scene information can cause visible artifacts. This can be tackled by keeping multiple layers of screen-space information, but might not be afforable on severely limited time-budgets. Traversal speed of single-layer ray marching is commonly improved by multi-resolution schemes, from sub-sampling to stepping through mip-maps to achieve faster frame rates. We show that by combining these approaches, keeping multiple layers and tracing on multiple resolutions, images of higher quality can be computed rapidly. Figure 1 shows this for two scenes with multi-bounce reflections that would show strong artifacts when using only a single layer.}, language = {en} } @inproceedings{NiessnerKuhnertSelgradetal., author = {Nießner, Matthias and Kuhnert, Nadine and Selgrad, Kai and Stamminger, Marc and Michelson, Georg}, title = {Real-time Simulation of Human Vision using Temporal Compositing with CUDA on the GPU}, series = {Proceedings 25th Workshop on Parallel Systems and Algorithms 2013 (PARS) ; April 11-12, 2013, Erlangen, Germany}, booktitle = {Proceedings 25th Workshop on Parallel Systems and Algorithms 2013 (PARS) ; April 11-12, 2013, Erlangen, Germany}, abstract = {We present a novel approach that simulates human vision including visual defects such as glaucoma by temporal composition of human vision in real-time on the GPU. Therefore, we determine eye focus points every time step and adapt the lens accommodation of our virtual eye model accordingly. The focal distance is then used to determine bluriness of observed scene regions; i.e., we compute defocus for all visible pixels. In order to simulate the visual memory we introduce a sharpness field where we integrate defocus values temporally. That allows for memorizing sharply perceived scene points. For visualization, we ray trace the virtual scene environment while incorporating depth of field based on the sharpness field data. Thus, our algorithm facilitates the simulation of human vision mimicing the visual memory. We consider this to be particularly useful for illustration purposes for patients with visual defects such as glaucoma. In order to run our algorithm in real-time we employ massively parallel graphics hardware.}, language = {en} } @inproceedings{SelgradReintgesPenketal., author = {Selgrad, Kai and Reintges, Christian and Penk, Dominik and Wagner, Pascal and Stamminger, Marc}, title = {Real-time Depth of Field Using Multi-layer Filtering}, series = {Proceedings of the 19th Symposium on Interactive 3D Graphics and Games (i3D '15), 27 February 2015 - 1 March 2015, San Francisco California}, booktitle = {Proceedings of the 19th Symposium on Interactive 3D Graphics and Games (i3D '15), 27 February 2015 - 1 March 2015, San Francisco California}, publisher = {ACM}, address = {New York, NY, USA}, isbn = {978-1-4503-3392-4}, doi = {10.1145/2699276.2699288}, pages = {121 -- 127}, abstract = {We present a novel technique for rendering depth of field that addresses difficult overlap cases, such as close, but out-of-focus, geometry in the near-field. Such scene configurations are not managed well by state-of-the-art post-processing approaches since essential information is missing due to occlusion. Our proposed algorithm renders the scene from a single camera position and computes a layered image using a single pass by constructing per-pixel lists. These lists can be filtered progressively to generate differently blurred representations of the scene. We show how this structure can be exploited to generate depth of field in real-time, even in complicated scene constellations.}, language = {en} } @inproceedings{SelgradMuellerStamminger, author = {Selgrad, Kai and M{\"u}ller, Jonas and Stamminger, Marc}, title = {Faster Ray-Traced Shadows for Hybrid Rendering of Fully Dynamic Scenes by Pre-BVH Culling}, series = {Smart Tools and Apps for Graphics - Eurographics Italian Chapter Conference}, booktitle = {Smart Tools and Apps for Graphics - Eurographics Italian Chapter Conference}, editor = {Giachetti, Andrea and Biasotti, Silvia and Tarini, Marco}, publisher = {The Eurographics Association}, isbn = {978-3-905674-97-2}, doi = {10.2312/stag.20151295}, abstract = {With ever increasing ray traversal and hierarchy construction performance the application of ray tracing to problems often tackled by rasterization-based algorithms is becoming a viable alternative. This is especially desirable as the ground truth for these algorithms is often determined by using ray tracing and thus directly applying it is the simplest way to generate images satisfying the reference. In this paper we propose a very efficient pre-process to speed up the construction and traversal of sub-optimal, but fast-to-build hierarchies used for interactive ray tracing and show how it can be applied to shadow rays in a hybrid environment, where ray tracing is used to sample area lights for scene positions found and shaded via rasterization.}, language = {en} } @inproceedings{LierSelgradStamminger, author = {Lier, Alexander and Selgrad, Kai and Stamminger, Marc}, title = {DIY Meta Languages with Common Lisp}, series = {Proceedings of the 10th European Lisp Symposium (ELS 2017), Vrije Universiteit Brussel, Brussels, Belgium, April, 3-4 2017}, booktitle = {Proceedings of the 10th European Lisp Symposium (ELS 2017), Vrije Universiteit Brussel, Brussels, Belgium, April, 3-4 2017}, editor = {Alberto Riva,}, publisher = {ACM}, address = {New York, NY, USA}, isbn = {978-2-9557474-1-4}, pages = {72 -- 79}, abstract = {In earlier work we described C-Mera, an S-Expression to C-style code transformator, and how it can be used to provide high-level abstractions to the C-family of programming languages. In this paper we provide an in-depth description of its internals that would have been out of the scope of the earlier presentations. Œese implementation details are presented as a toolkit of general techniques for implementing similar meta languages on top of Common Lisp and illustrated on the example of C-Mera, with the goal of making our experience in implementing them more broadly available.}, language = {en} } @inproceedings{SelgradLierWittmannetal., author = {Selgrad, Kai and Lier, Alexander and Wittmann, Markus and Lohmann, Daniel and Stamminger, Marc}, title = {Defmacro for C: Lightweight, Ad Hoc Code Generation}, series = {Proceedings of ELS 2014 7th European Lisp Symposium ; May 5 - 6 2014, IRCAM, Paris, France}, booktitle = {Proceedings of ELS 2014 7th European Lisp Symposium ; May 5 - 6 2014, IRCAM, Paris, France}, issn = {2677-3465}, pages = {80 -- 87}, abstract = {We describe the design and implementation of CGen, a C code generator with support for Common Lisp-style macro expansion. Our code generator supports the simple and efficient management of variants, ad hoc code generation to capture reoccurring patterns, composable abstractions as well as the implementation of embedded domain specific languages by using the Common Lisp macro system. We demonstrate the applicability of our approach by numerous examples from small scale convenience macros over embedded languages to real-world applications in high-performance computing.}, language = {en} } @article{SelgradLierMartineketal., author = {Selgrad, Kai and Lier, Alexander and Martinek, Magdalena and Buchenau, Christoph and Guthe, Michael and Kranz, Franziska and Sch{\"a}fer, Henry and Stamminger, Marc}, title = {A Compressed Representation for Ray Tracing Parametric Surfaces}, series = {ACM Transactions on Graphics}, volume = {36}, journal = {ACM Transactions on Graphics}, number = {1}, publisher = {ACM}, address = {New York, NY, USA}, doi = {10.1145/2953877}, pages = {1 -- 13}, abstract = {Parametric surfaces are an essential modeling tool in computer aided design and movie production. Even though their use is well established in industry, generating ray-traced images adds significant cost in time and memory consumption. Ray tracing such surfaces is usually accomplished by subdividing the surfaces on-the-fly, or by conversion to a polygonal representation. However, on-the-fly subdivision is computationally very expensive, whereas polygonal meshes require large amounts of memory. This is a particular problem for parametric surfaces with displacement, where very fine tessellation is required to faithfully represent the shape. Hence, memory restrictions are the major challenge in production rendering. In this paper, we present a novel solution to this problem. We propose a compression scheme for a-priori Bounding Volume Hierarchies (BVHs) on parametric patches, that reduces the data required for the hierarchy by a factor of up to 48. We further propose an approximate evaluation method that does not require leaf geometry, yielding an overall reduction of memory consumption by a factor of 60 over regular BVHs on indexed face sets and by a factor of 16 over established state-of-the-art compression schemes. Alternatively, our compression can simply be applied to a standard BVH while keeping the leaf geometry, resulting in a compression rate of up to 2:1 over current methods. Although decompression generates additional costs during traversal, we can manage very complex scenes even on the memory restrictive GPU at competitive render times.}, language = {en} } @inproceedings{FrankeHofmannStammingeretal., author = {Franke, Linus and Hofmann, Nikolai and Stamminger, Marc and Selgrad, Kai}, title = {Multi-Layer Depth of Field Rendering with Tiled Splatting}, series = {Proceedings of the ACM on Computer Graphics and Interactive Techniques}, volume = {1}, booktitle = {Proceedings of the ACM on Computer Graphics and Interactive Techniques}, number = {1}, publisher = {Association for Computing Machinery (ACM)}, address = {New York, NY, USA}, doi = {10.1145/3203200}, pages = {1 -- 17}, abstract = {In this paper we present a scattering-based method to compute high quality depth of field in real time. Relying on multiple layers of scene data, our method naturally supports settings with partial occlusion, an important effect that is often disregarded by real time approaches. Using well-founded layer-reduction techniques and efficient mapping to the GPU, our approach out-performs established approaches with a similar high-quality feature set. Our proposed algorithm works by collecting a multi-layer image, which is then directly reduced to only keep hidden fragments close to discontinuities. Fragments are then further reduced by merging and then splatted to screen-space tiles. The per-tile information is then sorted and accumulated in order, yielding an overall approach that supports partial occlusion as well as properly ordered blending of the out-of-focus fragments.}, language = {en} } @article{SelgradDachsbacherMeyeretal., author = {Selgrad, Kai and Dachsbacher, C. and Meyer, Q. and Stamminger, M.}, title = {Filtering Multi-Layer Shadow Maps for Accurate Soft Shadows}, series = {Computer Graphics Forum}, volume = {34}, journal = {Computer Graphics Forum}, number = {1}, publisher = {Wiley}, organization = {Wiley}, doi = {10.1111/cgf.12506}, pages = {205 -- 215}, abstract = {In this paper, we introduce a novel technique for pre-filtering multi-layer shadow maps. The occluders in the scene are stored as variable-length lists of fragments for each texel. We show how this representation can be filtered by progressively merging these lists. In contrast to previous pre-filtering techniques, our method better captures the distribution of depth values, resulting in a much higher shadow quality for overlapping occluders and occluders with different depths. The pre-filtered maps are generated and evaluated directly on the GPU, and provide efficient queries for shadow tests with arbitrary filter sizes. Accurate soft shadows are rendered in real-time even for complex scenes and difficult setups. Our results demonstrate that our pre-filtered maps are general and particularly scalable.}, language = {en} } @inproceedings{SelgradFrankeStamminger, author = {Selgrad, Kai and Franke, Linus and Stamminger, Marc}, title = {Tiled Depth of Field Splatting}, series = {EUROGRAPHICS 2016 (EG 2016) : Lisbon, Portugal, May 9th-13th, 2016 ; Posters}, booktitle = {EUROGRAPHICS 2016 (EG 2016) : Lisbon, Portugal, May 9th-13th, 2016 ; Posters}, editor = {Gonzaga Magalh{\~a}es, Luis and Mantiuk, Rafal}, publisher = {The Eurographics Association}, doi = {10.2312/egp.20161056}, pages = {39 -- 40}, abstract = {We present a method to compute post-processing depth of field (DOF) that produces more accurate results than previous approaches. Our method is based on existing approaches, namely DOF rendering by splatting and fast, tile-based particle accumulation. Using tile-based accumulation allows us to correctly sort out of focus pixels and apply proper alpha-blending to avoid artifacts commonly encountered with filter-based depth of field methods.}, language = {en} } @article{MauererSawallischHillieretal., author = {Mauerer, Wolfgang and Sawallisch, J. and Hillier, G. and Oberth{\"u}r, S. and H{\"o}nick, S.}, title = {Real-Time Android: Achieving determinism and ease of use}, series = {Embedded Wold Conference; Nuremberg, Germany, February 25, 2014 - February 27, 2014}, journal = {Embedded Wold Conference; Nuremberg, Germany, February 25, 2014 - February 27, 2014}, pages = {1 -- 7}, language = {en} } @article{ChristBrechtMauereretal., author = {Christ, Andreas and Brecht, Benjamin and Mauerer, Wolfgang and Silberhorn, Christine}, title = {Theory of quantum frequency conversion and type-II parametric down-conversion in the high-gain regime}, series = {New Journal of Physics}, volume = {15}, journal = {New Journal of Physics}, number = {5}, publisher = {IOP}, doi = {10.1088/1367-2630/15/5/053038}, abstract = {Frequency conversion (FC) and type-II parametric down-conversion (PDC) processes serve as basic building blocks for the implementation of quantum optical experiments: type-II PDC enables the efficient creation of quantum states such as photon-number states and Einstein-Podolsky-Rosen (EPR)-states. FC gives rise to technologies enabling efficient atom-photon coupling, ultrafast pulse gates and enhanced detection schemes. However, despite their widespread deployment, their theoretical treatment remains challenging. Especially the multi-photon components in the high-gain regime as well as the explicit time-dependence of the involved Hamiltonians hamper an efficient theoretical description of these nonlinear optical processes. In this paper, we investigate these effects and put forward two models that enable a full description of FC and type-II PDC in the high-gain regime. We present a rigorous numerical model relying on the solution of coupled integro-differential equations that covers the complete dynamics of the process. As an alternative, we develop a simplified model that, at the expense of neglecting time-ordering effects, enables an analytical solution. While the simplified model approximates the correct solution with high fidelity in a broad parameter range, sufficient for many experimental situations, such as FC with low efficiency, entangled photon-pair generation and the heralding of single photons from type-II PDC, our investigations reveal that the rigorous model predicts a decreased performance for FC processes in quantum pulse gate applications and an enhanced EPR-state generation rate during type-II PDC, when EPR squeezing values above 12 dB are considered.}, language = {en} } @article{GabrielWittmannSychetal., author = {Gabriel, Christian and Wittmann, Christoffer and Sych, Denis and Dong, Ruifang and Mauerer, Wolfgang and Andersen, Ulrik L. and Marquardt, Christoph and Leuchs, Gerd}, title = {A generator for unique quantum random numbers based on vacuum states}, series = {Nature Photonics}, volume = {4}, journal = {Nature Photonics}, number = {10}, publisher = {Springer}, organization = {Springer}, doi = {10.1038/nphoton.2010.197}, pages = {711 -- 715}, abstract = {Random numbers are a valuable component in diverse applications that range from simulations over gambling to cryptography. The quest for true randomness in these applications has engendered a large variety of different proposals for producing random numbers based on the foundational unpredictability of quantum mechanics4,5,6,7,8,9,10,11. However, most approaches do not consider that a potential adversary could have knowledge about the generated numbers, so the numbers are not verifiably random and unique12,13,14,15. Here we present a simple experimental setup based on homodyne measurements that uses the purity of a continuous-variable quantum vacuum state to generate unique random numbers. We use the intrinsic randomness in measuring the quadratures of a mode in the lowest energy vacuum state, which cannot be correlated to any other state. The simplicity of our source, combined with its verifiably unique randomness, are important attributes for achieving high-reliability, high-speed and low-cost quantum random number generators.}, language = {en} } @article{HelwigMauererSilberhorn, author = {Helwig, Wolfram and Mauerer, Wolfgang and Silberhorn, Christine}, title = {Multimode states in decoy-based quantum-key-distribution protocols}, series = {Physical Review A}, volume = {80}, journal = {Physical Review A}, number = {5}, publisher = {American Physical Society}, doi = {10.1103/physreva.80.052326}, abstract = {Every security analysis of quantum-key distribution (QKD) relies on a faithful modeling of the employed quantum states. Many photon sources, such as for instance a parametric down-conversion (PDC) source, require a multimode description but are usually only considered in a single-mode representation. In general, the important claim in decoy-based QKD protocols for indistinguishability between signal and decoy states does not hold for all sources. We derive bounds on the single-photon transmission probability and error rate for multimode states and apply these bounds to the output state of a PDC source. We observe two opposing effects on the secure key rate. First, the multimode structure of the state gives rise to a new attack that decreases the key rate. Second, more contributing modes change the photon number distribution from a thermal toward a Poissonian distribution, which increases the key rate.}, language = {en} } @article{ColdenstrodtRongeLundeenPregnelletal., author = {Coldenstrodt-Ronge, Hendrik B. and Lundeen, Jeff S. and Pregnell, Kenny L. and Feito, Alvaro and Smith, Brian J. and Mauerer, Wolfgang and Silberhorn, Christine and Eisert, Jens and Plenio, Martin B. and Walmsley, Ian A.}, title = {A proposed testbed for detector tomography}, series = {Journal of Modern Optics}, volume = {56}, journal = {Journal of Modern Optics}, number = {2-3}, publisher = {Taylor\&Francis}, doi = {10.1080/09500340802304929}, pages = {432 -- 441}, abstract = {Measurement is the only part of a general quantum system that has yet to be characterised experimentally in a complete manner. Detector tomography provides a procedure for doing just this; an arbitrary measurement device can be fully characterised, and thus calibrated, in a systematic way without access to its components or its design. The result is a reconstructed POVM containing the measurement operators associated with each measurement outcome. We consider two detectors, a single-photon detector and a photon-number counter, and propose an easily realised experimental apparatus to perform detector tomography on them. We also present a method of visualising the resulting measurement operators.}, language = {en} } @article{MauererHelwigSilberhorn, author = {Mauerer, Wolfgang and Helwig, Wolfram and Silberhorn, Christine}, title = {Recent developments in quantum key distribution: Theory and practice}, series = {Annalen der Physik}, volume = {17}, journal = {Annalen der Physik}, number = {2-3}, publisher = {Wiley}, doi = {10.1002/andp.200710284}, pages = {158 -- 175}, abstract = {Quantum key distribution is among the foremost applications of quantum mechanics, both in terms of fundamental physics and as a technology on the brink of commercial deployment. Starting from principal schemes and initial proofs of unconditional security for perfect systems, much effort has gone into providing secure schemes which can cope with numerous experimental imperfections unavoidable in real world implementations. In this paper, we provide a comparison of various schemes and protocols. We analyse their efficiency and performance when implemented with imperfect physical components. We consider how experimental faults are accounted for using effective parameters. We compare various recent protocols and provide guidelines as to which components propose best advances when being improved.}, language = {en} } @article{MauererAvenhausHelwigetal., author = {Mauerer, Wolfgang and Avenhaus, Malte and Helwig, Wolfram and Silberhorn, Christine}, title = {How colors influence numbers: Photon statistics of parametric down-conversion}, series = {Physical Review A (Phys. Rev. A)}, volume = {80}, journal = {Physical Review A (Phys. Rev. A)}, number = {5}, publisher = {American Physical Society}, doi = {10.1103/physreva.80.053815}, abstract = {Parametric down-conversion (PDC) is a technique of ubiquitous experimental significance in the production of nonclassical, photon-number-correlated twin beams. Standard theory of PDC as a two-mode squeezing process predicts and homodyne measurements observe a thermal photon number distribution per beam. Recent experiments have obtained conflicting distributions. In this article, we explain the observation by an a priori theoretical model solely based on directly accessible physical quantities. We compare our predictions with experimental data and find excellent agreement.}, language = {en} } @article{Mauerer, author = {Mauerer, Wolfgang}, title = {Datenvisualisierung mit Ggplot2}, series = {Linux-Magazin}, journal = {Linux-Magazin}, number = {3}, publisher = {Linux New Media AG}, abstract = {Wer seine Daten mit ansehnlichen und informativen Graphen veranschaulichen m{\"o}chte, braucht meist viel Geduld. Die R-Erweiterung Ggplot2 bringt System in die Grafik, dr{\"u}ckt sich in knappem Quellcode aus und bl{\"a}st frischen Wind in den Alltag der Datenvisualisierung.}, language = {en} } @article{RohdeMauererSilberhorn, author = {Rohde, Peter P. and Mauerer, Wolfgang and Silberhorn, Christine}, title = {Spectral structure and decompositions of optical states, and their applications}, series = {New Journal of Physics}, volume = {9}, journal = {New Journal of Physics}, number = {4}, publisher = {IOP Publishing}, doi = {10.1088/1367-2630/9/4/091}, pages = {91}, abstract = {We discuss the spectral structure and decomposition of multi-photon states. Ordinarily 'multi-photon states' and 'Fock states' are regarded as synonymous. However, when the spectral degrees of freedom are included this is not the case, and the class of 'multi-photon' states is much broader than the class of 'Fock' states. We discuss the criteria for a state to be considered a Fock state. We then address the decomposition of general multi-photon states into bases of orthogonal eigenmodes, building on existing multi-mode theory, and introduce an occupation number representation that provides an elegant description of such states. This representation allows us to work in bases imposed by experimental constraints, simplifying calculations in many situations. Finally we apply this technique to several example situations, which are highly relevant for state of the art experiments. These include Hong-Ou-Mandel interference, spectral filtering, finite bandwidth photo-detection, homodyne detection and the conditional preparation of Schr{\"o}dinger kitten and Fock states. Our techniques allow for very simple descriptions of each of these examples.}, language = {en} } @article{Jain, author = {Jain, Brijnesh}, title = {Making the dynamic time warping distance warping-invariant}, series = {Pattern Recognition}, volume = {94}, journal = {Pattern Recognition}, number = {October}, publisher = {Elsevier}, doi = {10.1016/j.patcog.2019.05.016}, pages = {35 -- 52}, abstract = {The literature postulates that the dynamic time warping (dtw) distance can cope with temporal variations but stores and processes time series in a form as if the dtw-distance cannot cope with such variations. To address this inconsistency, we first show that the dtw-distance is not warping-invariant—despite its name and contrary to its characterization in some publications. The lack of warping-invariance contributes to the inconsistency mentioned above and to a strange behavior. To eliminate these peculiarities, we convert the dtw-distance to a warping-invariant semi-metric, called time-warp-invariant (twi) distance. Empirical results suggest that the error rates of the twi and dtw nearest-neighbor classifier are practically equivalent in a Bayesian sense. However, the twi-distance requires less storage and computation time than the dtw-distance for a broad range of problems. These results challenge the current practice of applying the dtw-distance in nearest-neighbor classification and suggest the proposed twi-distance as a more efficient and consistent option.}, language = {en} } @article{MauererSilberhorn, author = {Mauerer, Wolfgang and Silberhorn, Christine}, title = {Quantum key distribution with passive decoy state selection}, series = {Physical Review A}, volume = {75}, journal = {Physical Review A}, number = {5}, publisher = {American Physical Society}, doi = {10.1103/physreva.75.050305}, abstract = {We propose a quantum key distribution scheme which closely matches the performance of a perfect single photon source. It nearly attains the physical upper bound in terms of key generation rate and maximally achievable distance. Our scheme relies on a practical setup based on a parametric downconversion source and present day, nonideal photon-number detection. Arbitrary experimental imperfections which lead to bit errors are included. We select decoy states by classical postprocessing. This allows one to improve the effective signal statistics and achievable distance.}, language = {en} } @book{Mauerer, author = {Mauerer, Wolfgang}, title = {Professional Linux kernel architecture}, series = {Wrox professional guides}, journal = {Wrox professional guides}, publisher = {Wiley}, address = {Indianapolis}, isbn = {9780470343432}, abstract = {Find an introduction to the architecture, concepts and algorithms of the Linux kernel in Professional Linux Kernel Architecture, a guide to the kernel sources and large number of connections among subsystems. Find an introduction to the relevant structures and functions exported by the kernel to userland, understand the theoretical and conceptual aspects of the Linux kernel and Unix derivatives, and gain a deeper understanding of the kernel. Learn how to reduce the vast amount of information contained in the kernel sources and obtain the skills necessary to understand the kernel sources.}, language = {en} } @book{Mauerer, author = {Mauerer, Wolfgang}, title = {Textverarbeitung mit LATEX 2e [2 epsilon] unter UNIX}, publisher = {Hanser}, address = {M{\"u}nchen}, isbn = {9783446189096}, language = {de} }