TY - JOUR A1 - Heckner, Markus A1 - Schworm, Silke T1 - The tagblog: Exploring social web user contribution to encourage students to actively engage in learning content JF - International Journal of Web Based Communities N2 - After leaving the lecture hall, students hardly reflect about the lesson's contents. To foster learning, the lesson content should be reorganised, elaborated and critically reflected. Tagging and blogging offer the opportunity to actively engage students in follow-up course work. This paper presents the results of a case study exploring the use of a social web application to encourage student contributions within the context of an undergraduate university seminar. The tagblog combines blogging, tagging and rating as three forms of online user contribution on Web 2.0 to develop a shared, emergent group knowledge repository. Blog posts, tags and comments are analysed to examine how user contributions reflect the active processing of learning content. KW - web 20 KW - social web KW - higher education KW - contribution KW - learning content KW - student participation KW - universities KW - tagging KW - tags KW - blogging KW - blogs KW - weblogs KW - rating KW - undergraduate seminars Y1 - 2009 U6 - https://doi.org/10.1504/IJWBC.2009.028088 SN - 1741-8216 SN - 1477-8394 VL - 5 IS - 4 SP - 528 EP - 542 PB - Inderscience Enterprises CY - Olney ER - TY - JOUR A1 - Heckner, Markus A1 - Wolff, Christian T1 - Wissensmanagement mit Social Software [Editorial] JF - Information - Wissenschaft und Praxis : IWP Y1 - 2009 UR - https://www.b-i-t-online.de/pdf/iwp/IWP2009-4.pdf SN - 1619-4292 SN - 1434-4653 VL - 60 IS - 4 SP - 185 EP - 187 PB - DGI ; De Gruyter CY - Frankfurt, Main ; Berlin ; New York ER - TY - CHAP A1 - Middel, Luise A1 - Popp, Christof A1 - Raptis, Georgios A1 - Sutter, Tamara A1 - Gutbrod, Max T1 - Konzeption und Aufbau einer technischen Telepräsenzrobotik-Plattform für die Unterstützung von Schlaganfallpatient*innen in der Pflege, Logopädie und Physiotherapie T2 - Digitale Technik für ambulante Pflege und Therapie Y1 - 2022 U6 - https://doi.org/10.1515/9783839462355-002 SP - 19 EP - 58 PB - de Gruyter CY - Berlin ER - TY - CHAP A1 - Braun, Stefan A1 - Schildgen, Johannes A1 - Deßloch, Stefan T1 - Visualization of NoSQL transformations using sampling techniques | Visualisierung von NoSQL-Transformationen unter der Verwendung von Sampling-Techniken T2 - Proceedings of the LWA 2015 workshops: KDML, FGWM, IR, and FGDB : Trier, Germany, October 7-9, 2015 N2 - Analysen auf NoSQL-Datenbanken sind oft langdauernd und die Ergebnisse fur den Benutzer haufig schwer verst ̈andlich. Wir prasentieren eine Möglichkeit, Datenmengen aus Wide-Column Stores mittels der Transformationssprache NotaQL zu transformieren sowie zu aggregieren und die Ergebnisse in Form von Diagrammen dem Benutzer darzustellen. Dabei kommen Sampling-Techniken zum Einsatz, um die Berechnung auf Kosten der Genauigkeit zu beschleunigen. Das von uns verwendete iterative Samplingverfahren sorgt fur eine kontinuierliche Verbesserung der Berechnungsgenauigkeit und bietet zudem Möglichkeiten zur Genauigkeitsabschätzung, die in Form von Konfidenzintervallen in den Diagrammen dargestellt werden kann. Y1 - 2015 UR - https://ceur-ws.org/Vol-1458/H06_CRC77_Braun.pdf SP - 427 EP - 438 PB - RWTH Aachen CY - Aachen ER - TY - JOUR A1 - Haertl, Petra Maria A1 - Löschel, Rainer A1 - Repp, Natalia A1 - Pohl, Fabian A1 - Kölbl, Oliver A1 - Dobler, Barbara T1 - Frameless fractionated stereotactic radiation therapy of intracranial lesions: Impact of cone beam CT based setup correction on dose distribution JF - Radiation Oncology N2 - Background The purpose of this study was to evaluate the impact of Cone Beam CT (CBCT) based setup correction on total dose distributions in fractionated frameless stereotactic radiation therapy of intracranial lesions. Methods Ten patients with intracranial lesions treated with 30 Gy in 6 fractions were included in this study. Treatment planning was performed with Oncentra® for a SynergyS® (Elekta Ltd, Crawley, UK) linear accelerator with XVI® Cone Beam CT, and HexaPOD™ couch top. Patients were immobilized by thermoplastic masks (BrainLab, Reuther). After initial patient setup with respect to lasers, a CBCT study was acquired and registered to the planning CT (PL-CT) study. Patient positioning was corrected according to the correction values (translational, rotational) calculated by the XVI® system. Afterwards a second CBCT study was acquired and registered to the PL-CT to confirm the accuracy of the corrections. An in-house developed software was used for rigid transformation of the PL-CT to the CBCT geometry, and dose calculations for each fraction were performed on the transformed CT. The total dose distribution was achieved by back-transformation and summation of the dose distributions of each fraction. Dose distributions based on PL-CT, CBCT (laser set-up), and final CBCT were compared to assess the influence of setup inaccuracies. Results The mean displacement vector, calculated over all treatments, was reduced from (4.3 ± 1.3) mm for laser based setup to (0.5 ± 0.2) mm if CBCT corrections were applied. The mean rotational errors around the medial-lateral, superior-inferior, anterior-posterior axis were reduced from (−0.1 ± 1.4)°, (0.1 ± 1.2)° and (−0.2 ± 1.0)°, to (0.04 ± 0.4)°, (0.01 ± 0.4)° and (0.02 ± 0.3)°. As a consequence the mean deviation between planned and delivered dose in the planning target volume (PTV) could be reduced from 12.3% to 0.4% for D95 and from 5.9% to 0.1% for Dav. Maximum deviation was reduced from 31.8% to 0.8% for D95, and from 20.4% to 0.1% for Dav. Conclusion Real dose distributions differ substantially from planned dose distributions, if setup is performed according to lasers only. Thermoplasic masks combined with a daily CBCT enabled a sufficient accuracy in dose distribution. KW - CBCT KW - Setup error KW - Reproducibility KW - Daily dose distribution KW - Cumulative dose distribution KW - Actual dose distribution KW - Intracranial lesions Y1 - 2013 U6 - https://doi.org/10.1186/1748-717X-8-153 VL - 8 IS - 1 PB - BioMed Central CY - London ER - TY - JOUR A1 - Högele, Wolfgang A1 - Dobler, Barbara A1 - Kölbl, Oliver A1 - Beard, Clair A1 - Zygmanski, Piotr A1 - Löschel, Rainer T1 - Stochastic triangulation for prostate positioning during radiotherapy using short CBCT arcs JF - Radiotherapy and Oncology N2 - Background and purpose: Fast and reliable tumor localization is an important part of today's radiotherapy utilizing new delivery techniques. This proof-of-principle study demonstrates the use of a method called herein 'stochastic triangulation' for this purpose. Stochastic triangulation uses very short imaging arcs and a few projections. Materials and methods: A stochastic Maximum A Posteriori (MAP) estimator is proposed based on an uncertainty-driven model of the acquisition geometry and inter-/intra-fractional deformable anatomy. The application of this method was designed to use the available linac-mounted cone-beam computed tomography (CBCT) and/or electronic portal imaging devices (EPID) for the patient setup based on short imaging arcs. For the proof-of-principle clinical demonstration, the MAP estimator was applied to 5 CBCT scans of a prostate cancer patient with 2 implanted gold markers. Estimation was performed for several (18) very short imaging arcs of 5° with 10 projections resulting in 90 estimations. Results: Short-arc stochastic triangulation led to residual radial errors compared to manual inspection with a mean value of 1.4mm and a standard deviation of 0.9 mm (median 1.2mm, maximum 3.8mm) averaged over imaging directions all around the patient. Furthermore, abrupt intra-fractional motion of up to 10mm resulted in radial errors with a mean value of 1.8mm and a standard deviation of 1.1mm (median 1.5mm, maximum 5.6mm). Slow periodic intra-fractional motions in the range of 12 mm resulted in radial errors with a mean value of 1.8mm and a standard deviation of 1.1mm (median 1.6mm, maximum 4.7 mm). Conclusion: Based on this study, the proposed stochastic method is fast, robust and can be used for inter- as well as intra-fractional target localization using current CBCT units. KW - Patient positioning KW - Setup error KW - Maximum A Posteriori estimation KW - Short arc KW - Stochastic triangulation Y1 - 2013 U6 - https://doi.org/10.1016/j.radonc.2013.01.005 VL - 106 IS - 2 SP - 241 EP - 249 PB - Elsevier ER - TY - JOUR A1 - Högele, Wolfgang A1 - Zygmanski, Piotr A1 - Dobler, Barbara A1 - Kroiss, M. A1 - Kölbl, Oliver A1 - Löschel, Rainer T1 - Localization of deformable tumors from short-arc projections using Bayesian estimation JF - Medical Physics N2 - Purpose: The authors present a stochastic framework for radiotherapy patient positioning directly utilizing radiographic projections. This framework is developed to be robust against anatomical nonrigid deformations and to cope with challenging imaging scenarios, involving only a few cone beam CT projections from short arcs. Methods: Specifically, a Bayesian estimator (BE) is explicitly derived for the given scanning geometry. This estimator is compared to reference methods such as chamfer matching (CM) and the minimization of the median absolute error adapted as tools of robust image processing and statistics. In order to show the performance of the stochastic short-arc patient positioning method, a CIRS IMRT thorax phantom study is presented with movable markers and the utilization of an Elekta Synergy® XVI system. Furthermore, a clinical prostate CBCT scan of a Varian® On-Board Imager® system is utilized to investigate the robustness of the method for large variations of image quality (anterior-posterior vs lateral views). Results: The results show that the BE shifts reduce the initial setup error of up to 3 cm down to 3 mm at maximum for an imaging arc as short as 10° while CM achieves residual errors of 7 mm at maximum only for arcs longer than 40°. Furthermore, the BE can compensate robustly for low image qualities using several low quality projections simultaneously. Conclusions: In conclusion, an estimation method for marker-based patient positioning for short imaging arcs is presented and shown to be robust and accurate for deformable anatomies. Y1 - 2012 U6 - https://doi.org/10.1118/1.4764483 VL - 39 IS - 12 SP - 7205 EP - 7214 PB - Wiley ER - TY - JOUR A1 - auf der Heide, Friedhelm Meyer A1 - Schindelhauer, Christian A1 - Volbert, Klaus A1 - Grünewald, Matthias T1 - Congestion, dilation, and energy in radio networks JF - Theory of Computing Systems N2 - We investigate the problem of path selection in radio networks for a given static set of n sites in two- and three-dimensional space. For static point-to-point communication we define measures for congestion, dilation, and energy consumption that take interferences among communication links into account. We show that energy-optimal path selection for radio networks can be computed in polynomial time. Then we introduce the diversity g(V) of a set V ⫅ ℝd for any constant d. It can be used to upper bound the number of interfering edges. For real-world applications it can be regarded as Θ(log n). A main result is that a c-spanner construction as a communication network allows one to approximate the congestion-optimal path system by a factor of O(g(V)2). Furthermore, we show that there are vertex sets where only one of the performance parameters congestion, dilation, and energy can be optimized at a time. We show trade-offs lower bounding congestion × dilation and dilation × energy. The trade-off between congestion and dilation increases with switching from two-dimensional to three-dimensional space. For congestion and energy the situation is even worse. It is only possible to find a reasonable approximation for either congestion or energy minimization, while the other parameter is at least a polynomial factor worse than in the optimal network. KW - Medium Access Control KW - Minimum Span Tree KW - Communication Link KW - Unit Energy KW - Radio Station Y1 - 2004 U6 - https://doi.org/10.1007/s00224-004-1124-z VL - 37 IS - 3 SP - 343 EP - 370 PB - Springer Nature ER - TY - JOUR A1 - Högele, Wolfgang A1 - Löschel, Rainer A1 - Dobler, Barbara A1 - Kölbl, Oliver A1 - Zygmanski, Piotr T1 - Bayesian estimation applied to stochastic localization with constraints due to interfaces and boundaries JF - Mathematical Problems in Engineering N2 - Purpose We present a systematic Bayesian formulation of the stochastic localization/triangulation problem close to constraining interfaces. Methods For this purpose, the terminology of Bayesian estimation is summarized suitably for applied researchers including the presentation of Maximum Likelihood (ML), Maximum A Posteriori (MAP), and Minimum Mean Square Error (MMSE) estimation. Explicit estimators for triangulation are presented for the linear 2D parallel beam and the nonlinear 3D cone beam model. The priors in MAP and MMSE optionally incorporate (A) the hard constraints about the interface and (B) knowledge about the probability of the object with respect to the interface. All presented estimators are compared in several simulation studies for live acquisition scenarios with 10,000 samples each. Results First, the presented application shows that MAP and MMSE perform considerably better, leading to lower Root Mean Square Errors (RMSEs) in the simulation studies compared to the ML approach by typically introducing a bias. Second, utilizing priors including (A) and (B) is very beneficial compared to just including (A). Third, typically MMSE leads to better results than MAP, by the cost of significantly higher computational effort. Conclusion Depending on the specific application and prior knowledge, MAP and MMSE estimators strongly increase the estimation accuracy for localization close to interfaces. Y1 - 2013 U6 - https://doi.org/10.1155/2013/960421 SN - 1563-5147 VL - 213 PB - HIndawi ER - TY - JOUR A1 - Heckner, Markus A1 - Mühlbacher, Susanne A1 - Wolff, Christian T1 - Tagging tagging. Analysing user keywords in scientific bibliography management systems JF - Journal of Digital Information N2 - In this paper, an empirical study of tagging behaviour in web-based bibliographic annotation systems is presented. Starting from an initial category finding phase in which tags attributed to selected articles from Connotea were classified we have set up a category model for linguistic and functional aspects of tag usage as well as for the relationship between tags and document full text. In a second phase this model is applied to approx. 500 tagged articles from the information and computer technology domain randomly selected from Connotea. Our findings show significant differences to other tagging research which was primarily conducted using popular (non-scientific) tagging platforms like Flickr or Delicious. We observe a great overlap of tag material and document text and rather few non-content related tags. The comparison of user tags with author keywords shows that users tend to use less and more general tags. Finally, system functionality seems to play a role for users’ tagging behaviour. Y1 - 2008 UR - https://jodi-ojs-tdl.tdl.org/jodi/article/view/246 VL - 9 IS - 2 PB - Multimedia Research Group ER - TY - JOUR A1 - Hager, Markus A1 - Finke, Thomas A1 - Seitz, Jochen A1 - Waas, Thomas T1 - Software-based management for Ethernet networks JF - Wireless Personal Communications N2 - An adequate network management is an essential part for each network permitting to keep the network performance at a suitable level. In this paper, we present our work focusing on an Ethernet network which is used as background interconnection technology for a smart home system in large buildings like tenements or an office block. In this case the network is larger and especially the applications are quite heterogeneous as compared to a private smart home system. Therefore, it is hard to supply a fair and quality of service aware network meeting all the demands. This is especially challenging in the case of an Ethernet network because this technology was intended to use it as a transparent connection system without the feature to support hard quality of service. We present how this problem could be solved by a middleware which best meets the special requirement of the mentioned use case. Finally, we discuss possible design improvements of this solution and present the recent Ethernet standards that could help solve this problem in an alternative way. KW - Network management KW - Ethernet KW - Middleware Y1 - 2014 U6 - https://doi.org/10.1007/s11277-013-1341-3 VL - 74 IS - 3 SP - 1021 EP - 1032 PB - Springer Nature ER -