@article{UndenBongaerts1997,
  author    = {Unden, Gottfried and Bongaerts, Johannes},
  title     = {Alternative respiratory pathways of Escherichia coli: energetics and transcriptional regulation in response to electron acceptors},
  series = {Biochimica et biophysica acta (BBA) - Bioenergetics},
  volume    = {Vol. 1320},
  journal   = {Biochimica et biophysica acta (BBA) - Bioenergetics},
  number    = {Iss. 3},
  issn      = {1879-2650 (E-Journal); 0005-2728 (Print)},
  pages     = {217 -- 234},
  year      = {1997},
  language  = {en}
}
@article{UndenBeckerBongaertsetal.1994,
  author    = {Unden, G. and Becker, S. and Bongaerts, Johannes and Schirawski, J. and Six, S.},
  title     = {Oxygen regulated gene expression in facultatively anaerobic bacteria},
  series = {Antonie van Leeuwenhoek},
  volume    = {Vol. 66},
  journal   = {Antonie van Leeuwenhoek},
  number    = {Iss. 1-3},
  issn      = {0003-6072 (Print) ; 1572-9699 (online)},
  pages     = {3 -- 22},
  year      = {1994},
  language  = {en}
}
@article{UndenBeckerBongaertsetal.1995,
  author    = {Unden, G. and Becker, S. and Bongaerts, Johannes and Holighaus, G. and Schirawski, J. and Six, S.},
  title     = {O2-sensing and O2-dependent gene regulation in facultatively anaerobic bacteria},
  series = {Archives of microbiology},
  volume    = {Vol. 164},
  journal   = {Archives of microbiology},
  number    = {Iss. 2},
  issn      = {1432-072X (E-Journal); 0003-9276 (Print); 0302-8933 (Print)},
  pages     = {81 -- 90},
  year      = {1995},
  language  = {en}
}
@article{UmutluOrzadaKinneretal.2011,
  author    = {Umutlu, Lale and Orzada, Stephan and Kinner, Sonja and Maderwald, Stefan and Bronte, Irina and Bitz, Andreas and Kraff, Oliver and Ladd, Susanne C. and Antoch, Gerald and Ladd, Mark E. and Quick, Harald H. and Lauenstein, Thomas C.},
  title     = {Renal imaging at 7 Tesla: preliminary results},
  series = {European Radiology},
  volume    = {21},
  journal   = {European Radiology},
  number    = {4},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {1432-1084},
  pages     = {841 -- 849},
  year      = {2011},
  abstract  = {Objective To investigate the feasibility of 7T MR imaging of the kidneys utilising a custom-built 8-channel transmit/receive radiofrequency body coil. Methods In vivo unenhanced MR was performed in 8 healthy volunteers on a 7T whole-body MR system. After B0 shimming the following sequences were obtained: 1) 2D and 3D spoiled gradient-echo sequences (FLASH, VIBE), 2) T1-weighted 2D in and opposed phase 3) True-FISP imaging and 4) a T2-weighted turbo spin echo (TSE) sequence. Visual evaluation of the overall image quality was performed by two radiologists. Results Renal MRI at 7T was feasible in all eight subjects. Best image quality was found using T1-weighted gradient echo MRI, providing high anatomical details and excellent conspicuity of the non-enhanced vasculature. With successful shimming, B1 signal voids could be effectively reduced and/or shifted out of the region of interest in most sequence types. However, T2-weighted TSE imaging remained challenging and strongly impaired because of signal heterogeneities in three volunteers. Conclusion The results demonstrate the feasibility and diagnostic potential of dedicated 7T renal imaging. Further optimisation of imaging sequences and dedicated RF coil concepts are expected to improve the acquisition quality and ultimately provide high clinical diagnostic value.},
  language  = {en}
}
@article{UmutluKraffFischeretal.2013,
  author    = {Umutlu, Lale and Kraff, Oliver and Fischer, Anja and Kinner, Sonja and Maderwald, Stefan and Nassenstein, Kai and Nensa, Felix and Gr{\"u}neisen, Johannes and Orzada, Stephan and Bitz, Andreas and Forsting, Michael and Ladd, Mark E. and Lauenstein, Thomas C.},
  title     = {Seven-Tesla MRI of the female pelvis},
  series = {European Radiology},
  volume    = {23},
  journal   = {European Radiology},
  number    = {9},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {1432-1084},
  doi       = {10.1007/s00330-013-2868-0},
  pages     = {2364 -- 2373},
  year      = {2013},
  language  = {en}
}
@article{UmutluBitzMaderwaldetal.2013,
  author    = {Umutlu, Lale and Bitz, Andreas and Maderwald, Stefan and Orzada, Stephan and Kinner, Sonja and Kraff, Oliver and Brote, Irina and Ladd, Susanne C. and Schroeder, Tobias and Forsting, Michael},
  title     = {Contrast-enhanced ultra-high-field liver MRI: a feasibility trial},
  series = {European Journal of Radiology},
  volume    = {82},
  journal   = {European Journal of Radiology},
  number    = {5},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0720-048X},
  doi       = {10.1016/j.ejrad.2011.07.004},
  pages     = {760 -- 767},
  year      = {2013},
  language  = {en}
}
@article{UmutluMaderwaldKinneretal.2013,
  author    = {Umutlu, L. and Maderwald, S. and Kinner, S. and Kraff, O. and Bitz, Andreas and Orzada, S. and Johst, S. and Wrede, K. and Forsting, M. and Ladd, M. E. and Lauenstein, T. C. and Quick, H. H.},
  title     = {First-pass contrast-enhanced renal MRA at 7 Tesla: initial results},
  series = {European Radiology},
  volume    = {23},
  journal   = {European Radiology},
  number    = {4},
  publisher = {Springer},
  address   = {Berlin},
  issn      = {1432-1084},
  doi       = {10.1007/s00330-012-2666-0},
  pages     = {1059 -- 1066},
  year      = {2013},
  language  = {en}
}
@inproceedings{UlmerMostafaWollert2022,
  author    = {Ulmer, Jessica and Mostafa, Youssef and Wollert, J{\"o}rg},
  title     = {Digital Twin Academy: From Zero to Hero through individual learning experiences},
  series = {Tagungsband AALE 2022 / Herausgegeben von der Hochschule f{\"u}r Technik, Wirtschaft und Kultur Leipzig},
  booktitle = {Tagungsband AALE 2022 / Herausgegeben von der Hochschule f{\"u}r Technik, Wirtschaft und Kultur Leipzig},
  isbn      = {978-3-910103-00-9},
  doi       = {10.33968/2022.33},
  url       = {http://nbn-resolving.de/urn:nbn:de:bsz:l189-qucosa2-776097},
  pages     = {1 -- 9},
  year      = {2022},
  abstract  = {Digital twins are seen as one of the key technologies of Industry 4.0. Although many research groups focus on digital twins and create meaningful outputs, the technology has not yet reached a broad application in the industry. The main reasons for this imbalance are the complexity of the topic, the lack of specialists, and the unawareness of the twin opportunities. The project "Digital Twin Academy" aims to overcome these barriers by focusing on three actions: Building a digital twin community for discussion and exchange, offering multi-stage training for various knowledge levels, and implementing realworld use cases for deeper insights and guidance. In this work, we focus on creating a flexible learning platform that allows the user to select a training path adjusted to personal knowledge and needs. Therefore, a mix of basic and advanced modules is created and expanded by individual feedback options. The usage of personas supports the selection of the appropriate modules.},
  language  = {en}
}
@inproceedings{UlmerBraunLaietal.2019,
  author    = {Ulmer, Jessica and Braun, Sebastian and Lai, Chow Yin and Cheng, Chi-Tsun and Wollert, J{\"o}rg},
  title     = {Generic integration of VR and AR in product lifecycles based on CAD models},
  series = {Proceedings of The 23rd World Multi-Conference on Systemics, Cybernetics and Informatics: WMSCI 2019},
  booktitle = {Proceedings of The 23rd World Multi-Conference on Systemics, Cybernetics and Informatics: WMSCI 2019},
  year      = {2019},
  language  = {en}
}
@article{UlmerBraunChengetal.2020,
  author    = {Ulmer, Jessica and Braun, Sebastian and Cheng, Chi-Tsun and Dowey, Steve and Wollert, J{\"o}rg},
  title     = {Human-Centered Gamification Framework for Manufacturing Systems},
  series = {Procedia CIRP},
  volume    = {93},
  journal   = {Procedia CIRP},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {2212-8271},
  doi       = {10.1016/j.procir.2020.04.076},
  pages     = {670 -- 675},
  year      = {2020},
  abstract  = {While bringing new opportunities, the Industry 4.0 movement also imposes new challenges to the manufacturing industry and all its stakeholders. In this competitive environment, a skilled and engaged workforce is a key to success. Gamification can generate valuable feedbacks for improving employees' engagement and performance. Currently, Gamification in workspaces focuses on computer-based assignments and training, while tasks that require manual labor are rarely considered. This research provides an overview of Enterprise Gamification approaches and evaluates the challenges. Based on that, a skill-based Gamification framework for manual tasks is proposed, and a case study in the Industry 4.0 model factory is shown.},
  language  = {en}
}
@inproceedings{UlmerBraunChengetal.2021,
  author    = {Ulmer, Jessica and Braun, Sebastian and Cheng, Chi-Tsun and Dowey, Steve and Wollert, J{\"o}rg},
  title     = {Adapting Augmented Reality Systems to the users' needs using Gamification and error solving methods},
  series = {Procedia CIRP},
  volume    = {104},
  booktitle = {Procedia CIRP},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {2212-8271},
  doi       = {10.1016/j.procir.2021.11.024},
  pages     = {140 -- 145},
  year      = {2021},
  abstract  = {Animations of virtual items in AR support systems are typically predefined and lack interactions with dynamic physical environments. AR applications rarely consider users' preferences and do not provide customized spontaneous support under unknown situations. This research focuses on developing adaptive, error-tolerant AR systems based on directed acyclic graphs and error resolving strategies. Using this approach, users will have more freedom of choice during AR supported work, which leads to more efficient workflows. Error correction methods based on CAD models and predefined process data create individual support possibilities. The framework is implemented in the Industry 4.0 model factory at FH Aachen.},
  language  = {en}
}
@inproceedings{UlmerBraunChengetal.2022,
  author    = {Ulmer, Jessica and Braun, Sebastian and Cheng, Chi-Tsun and Dowey, Steve and Wollert, J{\"o}rg},
  title     = {Usage of digital twins for gamification applications in manufacturing},
  series = {Procedia CIRP},
  volume    = {107},
  booktitle = {Procedia CIRP},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {2212-8271},
  doi       = {10.1016/j.procir.2022.05.044},
  pages     = {675 -- 680},
  year      = {2022},
  abstract  = {Gamification applications are on the rise in the manufacturing sector to customize working scenarios, offer user-specific feedback, and provide personalized learning offerings. Commonly, different sensors are integrated into work environments to track workers' actions. Game elements are selected according to the work task and users' preferences. However, implementing gamified workplaces remains challenging as different data sources must be established, evaluated, and connected. Developers often require information from several areas of the companies to offer meaningful gamification strategies for their employees. Moreover, work environments and the associated support systems are usually not flexible enough to adapt to personal needs. Digital twins are one primary possibility to create a uniform data approach that can provide semantic information to gamification applications. Frequently, several digital twins have to interact with each other to provide information about the workplace, the manufacturing process, and the knowledge of the employees. This research aims to create an overview of existing digital twin approaches for digital support systems and presents a concept to use digital twins for gamified support and training systems. The concept is based upon the Reference Architecture Industry 4.0 (RAMI 4.0) and includes information about the whole life cycle of the assets. It is applied to an existing gamified training system and evaluated in the Industry 4.0 model factory by an example of a handle mounting.},
  language  = {en}
}
@article{UlmerBraunChengetal.2022,
  author    = {Ulmer, Jessica and Braun, Sebastian and Cheng, Chi-Tsun and Dowey, Steve and Wollert, J{\"o}rg},
  title     = {Gamification of virtual reality assembly training: Effects of a combined point and level system on motivation and training results},
  series = {International Journal of Human-Computer Studies},
  volume    = {165},
  journal   = {International Journal of Human-Computer Studies},
  number    = {Art. No. 102854},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {1071-5819},
  doi       = {10.1016/j.ijhcs.2022.102854},
  year      = {2022},
  abstract  = {Virtual Reality (VR) offers novel possibilities for remote training regardless of the availability of the actual equipment, the presence of specialists, and the training locations. Research shows that training environments that adapt to users' preferences and performance can promote more effective learning. However, the observed results can hardly be traced back to specific adaptive measures but the whole new training approach. This study analyzes the effects of a combined point and leveling VR-based gamification system on assembly training targeting specific training outcomes and users' motivations. The Gamified-VR-Group with 26 subjects received the gamified training, and the Non-Gamified-VR-Group with 27 subjects received the alternative without gamified elements. Both groups conducted their VR training at least three times before assembling the actual structure. The study found that a level system that gradually increases the difficulty and error probability in VR can significantly lower real-world error rates, self-corrections, and support usages. According to our study, a high error occurrence at the highest training level reduced the Gamified-VR-Group's feeling of competence compared to the Non-Gamified-VR-Group, but at the same time also led to lower error probabilities in real-life. It is concluded that a level system with a variable task difficulty should be combined with carefully balanced positive and negative feedback messages. This way, better learning results, and an improved self-evaluation can be achieved while not causing significant impacts on the participants' feeling of competence.},
  language  = {en}
}
@article{UlmerBraunChengetal.2023,
  author    = {Ulmer, Jessica and Braun, Carsten and Cheng, Chi-Tsun and Dowey, Steve and Wollert, J{\"o}rg},
  title     = {A human factors-aware assistance system in manufacturing based on gamification and hardware modularisation},
  series = {International Journal of Production Research},
  journal   = {International Journal of Production Research},
  publisher = {Taylor \& Francis},
  issn      = {0020-7543 (Print)},
  doi       = {10.1080/00207543.2023.2166140},
  year      = {2023},
  abstract  = {Assistance systems have been widely adopted in the manufacturing sector to facilitate various processes and tasks in production environments. However, existing systems are mostly equipped with rigid functional logic and do not provide individual user experiences or adapt to their capabilities. This work integrates human factors in assistance systems by adjusting the hardware and instruction presented to the workers' cognitive and physical demands. A modular system architecture is designed accordingly, which allows a flexible component exchange according to the user and the work task. Gamification, the use of game elements in non-gaming contexts, has been further adopted in this work to provide level-based instructions and personalised feedback. The developed framework is validated by applying it to a manual workstation for industrial assembly routines.},
  language  = {en}
}
@article{UllrichGrottkeRossaintetal.2010,
  author    = {Ullrich, Sebastian and Grottke, Oliver and Rossaint, Rolf and Staat, Manfred and Deserno, Thomas M. and Kuhlen, Torsten},
  title     = {Virtual Needle Simulation with Haptics for Regional Anaesthesia},
  pages     = {1 -- 3},
  year      = {2010},
  language  = {en}
}
@inproceedings{UibelBlass2013,
  author    = {Uibel, Thomas and Blaß, Hans-Joachim},
  title     = {Joints with Dowel Type Fasteners in CLT structures},
  series = {Focus solid timber solutions : European Conference on Cross Laminated Timber (CLT); May 21-22, 2013, Graz University of Technology, Austria},
  booktitle = {Focus solid timber solutions : European Conference on Cross Laminated Timber (CLT); May 21-22, 2013, Graz University of Technology, Austria},
  organization    = {European Conference on Cross Laminated Timber <2013, Graz>},
  isbn      = {978-1-85790-181-8 ; 1-85790-181-9},
  pages     = {119 -- 134},
  year      = {2013},
  language  = {en}
}
@inproceedings{UibelBlass2006,
  author    = {Uibel, Thomas and Blaß, Hans Joachim},
  title     = {Load Carrying Capacity of Joints with Dowel Type Fasteners in Solid Wood Panels},
  series = {Proceedings. CIB-W18 Meeting 2006, Florence, Italy 2006},
  booktitle = {Proceedings. CIB-W18 Meeting 2006, Florence, Italy 2006},
  issn      = {0945-6996},
  pages     = {1 -- 10},
  year      = {2006},
  language  = {en}
}
@inproceedings{UibelBlass2007,
  author    = {Uibel, Thomas and Blaß, Hans Joachim},
  title     = {Edge Joints with Dowel Type Fasteners in Cross Laminated Timber},
  series = {Proceedings. CIB-W18 Meeting 2007, Bled, Slovenia 2007},
  booktitle = {Proceedings. CIB-W18 Meeting 2007, Bled, Slovenia 2007},
  issn      = {0945-6996},
  pages     = {1 -- 11},
  year      = {2007},
  language  = {en}
}
@inproceedings{UibelBlass2010,
  author    = {Uibel, Thomas and Blaß, Hans Joachim},
  title     = {Determining Suitable Spacings and Distances for Self-tapping Screws by Experimental and Numerical Studies},
  series = {Proceedings of the 11th World Conference on Timber Engineering, WCTE 2010 : World Conference on Timber Engineering; [June 20 - 24, 2010, Riva del Garda, Trento, Italy] . Vol. III, Riva del Garda, Italy 2010},
  booktitle = {Proceedings of the 11th World Conference on Timber Engineering, WCTE 2010 : World Conference on Timber Engineering; [June 20 - 24, 2010, Riva del Garda, Trento, Italy] . Vol. III, Riva del Garda, Italy 2010},
  editor    = {Cecotti, A.},
  pages     = {669 -- 670},
  year      = {2010},
  language  = {en}
}
@inproceedings{UibelBlass2010,
  author    = {Uibel, Thomas and Blaß, Hans Joachim},
  title     = {A new method to determine suitable spacings and distances for self-tapping screws},
  series = {Meeting ... / International Council for Research and Innovation in Building and Construction, Working Commission W18 - Timber Structures},
  volume    = {43},
  booktitle = {Meeting ... / International Council for Research and Innovation in Building and Construction, Working Commission W18 - Timber Structures},
  publisher = {Lehrstuhl f{\"u}r Ingenieurholzbau und Baukonstruktionen},
  address   = {Karlsruhe},
  issn      = {1864-1784},
  year      = {2010},
  abstract  = {The determination of spacing, edge and end distance requirements for self-tapping screws requires numerous and comprehensive insertion tests. Yet the results of such tests cannot be transferred to other types of screws or even to screws of different diameter because of differences in shape or geometry. To reduce the effort of insertion tests a new method was developed which allows the estimation of required spacings, distances and timber thickness.},
  language  = {en}
}