TY  - CHAP
A1  - Bitz, Andreas
A1  - Kraff, O.
A1  - Orzada, S.
A1  - Maderwald, S.
A1  - Brote, I.
A1  - Ladd, M.
T1  - Experimental and Numerical Assessment of RF Safety of Transmit Coils at 7 Tesla
T2  - ISMRM workshop on MR safety 2010 : RF heating of the human in MRI : workshop series. The Washington County Historic Courthouse, Stillwater, Minnesota, USA, 15 - 17 October 2010
Y1  - 2010
SN  - 978-1-62276-088-6
SP  - 195
ER  - 
TY  - CHAP
A1  - Scholl, Ingrid
A1  - Bartella, Alex
A1  - Moluluo, Cem
A1  - Ertural, Berat
A1  - Laing, Frederic
A1  - Suder, Sebastian
T1  - MedicVR : Acceleration and Enhancement Techniques for Direct Volume Rendering in Virtual Reality
T2  - Bildverarbeitung für die Medizin 2019 : Algorithmen – Systeme – Anwendungen
Y1  - 2019
SN  - 978-3-658-25326-4
U6  - https://doi.org/10.1007/978-3-658-25326-4_32
SP  - 152
EP  - 157
PB  - Springer Vieweg
CY  - Wiesbaden
ER  - 
TY  - CHAP
A1  - Serror, Martin
A1  - Henze, Martin
A1  - Hack, Sacha
A1  - Schuba, Marko
A1  - Wehrle, Klaus
T1  - Towards in-network security for smart homes
T2  - 13th International Conference on Availability, Reliability and Security, ARES 2018; Hamburg; Germany; 27 August 2018 through 30 August 2018
Y1  - 2018
SN  - 978-145036448-5
U6  - https://doi.org/10.1145/3230833.3232802
SP  - Article numer 3232802
ER  - 
TY  - CHAP
A1  - Rao, Deepak
A1  - Pathrose, Plato
A1  - Hüning, Felix
A1  - Sid, Jithin
T1  - An Approach for Validating Safety of Perception Software in Autonomous Driving Systems
T2  - Model-Based Safety and Assessment: 6th International Symposium, IMBSA 2019, Thessaloniki, Greece, October 16–18, 2019, Proceedings
N2  - The increasing complexity of Advanced Driver Assistance Systems (ADAS) presents a challenging task to validate safe and reliable performance of these systems under varied conditions. The test and validation of ADAS/AD with real test drives, although important, involves huge costs and time. Simulation tools provide an alternative with the added advantage of reproducibility but often use ideal sensors, which do not reflect real sensor output accurately. This paper presents a new validation methodology using fault injection, as recommended by the ISO 26262 standard, to test software and system robustness. In our work, we investigated and developed a tool capable of inserting faults at different software and system levels to verify its robustness. The scope of this paper is to cover the fault injection test for the Visteon’s DriveCore™ system, a centralized domain controller for Autonomous driving which is sensor agnostic and SoC agnostic. With this new approach, the validation of safety monitoring functionality and its behavior can be tested using real-world data instead of synthetic data from simulation tools resulting in having better confidence in system performance before proceeding with in-vehicle testing.
KW  - Advanced driver assistance systems (ADAS/AD)
KW  - ISO 26262
KW  - Safety-critical systems validation
KW  - Safety of the intended functionality (SOTIF)
Y1  - 2019
SN  - 978-3-030-32872-6
U6  - https://doi.org/10.1007/978-3-030-32872-6_20
SP  - 303
EP  - 316
PB  - Springer
CY  - Cham
ER  - 
TY  - JOUR
A1  - Orzada, Stephan
A1  - Solbach, Klaus
A1  - Gratz, Marcel
A1  - Brunheim, Sascha
A1  - Fiedler, Thomas M.
A1  - Johst, Sören
A1  - Bitz, Andreas
A1  - Shooshtary, Samaneh
A1  - Abuelhaija, Asjraf
A1  - Voelker, Maximilian N.
A1  - Rietsch, Stefan H. G.
A1  - Kraff, Oliver
A1  - Maderwald, Stefan
A1  - Flöser, Martina
A1  - Oehmingen, Mark
A1  - Quick, Harald H.
A1  - Ladd, Mark E.
T1  - A 32-channel parallel transmit system add-on for 7T MRI
JF  - Plos one
Y1  - 2019
U6  - https://doi.org/10.1371/journal.pone.0222452
ER  - 
TY  - CHAP
A1  - Dinghofer, Kai
A1  - Hartung, Frank
T1  - Analysis of Criteria for the Selection of Machine Learning Frameworks
T2  - 2020 International Conference on Computing, Networking and Communications (ICNC)
N2  - With the many achievements of Machine Learning in the past years, it is likely that the sub-area of Deep Learning will continue to deliver major technological breakthroughs [1]. In order to achieve best results, it is important to know the various different Deep Learning frameworks and their respective properties. This paper provides a comparative overview of some of the most popular frameworks. First, the comparison methods and criteria are introduced and described with a focus on computer vision applications: Features and Uses are examined by evaluating papers and articles, Adoption and Popularity is determined by analyzing a data science study. Then, the frameworks TensorFlow, Keras, PyTorch and Caffe are compared based on the previously described criteria to highlight properties and differences. Advantages and disadvantages are compared, enabling researchers and developers to choose a framework according to their specific needs.
Y1  - 2020
U6  - https://doi.org/10.1109/ICNC47757.2020.9049650
N1  - 2020 International Conference on Computing, Networking and Communications (ICNC), 17-20 February 2020, Big Island, HI, USA
SP  - 373
EP  - 377
PB  - IEEE
CY  - New York, NY
ER  - 
TY  - JOUR
A1  - Köhler, Klemens
T1  - A conflict theory perspective of IT attacks – consequences for IT security education
N2  - Cyberspace is "the environment formed by physical and non-physical components to store, modify, and exchange data using computer networks" (NATO CCDCOE). Beyond that, it is an environment where people interact. IT attacks are hostile, non-cooperative interactions that can be described with conflict theory. Applying conflict theory to IT security leads to different objectives for end-user education, requiring different formats like agency-based competence developing games.
Y1  - 2020
IS  - Preprint
ER  - 
TY  - CHAP
A1  - Müller, Tim M.
A1  - Altherr, Lena
A1  - Ahola, Marja
A1  - Schabel, Samuel
A1  - Pelz, Peter F.
T1  - Optimizing pressure screen systems in paper recycling: optimal system layout, component selection and operation
N2  - Around 60% of the paper worldwide is made from recovered paper. Especially adhesive contaminants, so called stickies, reduce paper quality. To remove stickies but at the same time keep as many valuable fibers as possible, multi-stage screening systems with several interconnected pressure screens are used. When planning such systems, suitable screens have to be selected and their interconnection as well as operational parameters have to be defined considering multiple conflicting objectives. In this contribution, we present a Mixed-Integer Nonlinear Program to optimize system layout, component selection and operation to find a suitable trade-off between output quality and yield.
KW  - Mixed-integer nonlinear problem
KW  - MINLP
KW  - Process engineering
KW  - Paper recycling
KW  - Multi-criteria optimization
Y1  - 2018
SN  - 978-3-030-18499-5
U6  - https://doi.org/10.1007/978-3-030-18500-8_44
SP  - 355
EP  - 361
PB  - Springer
CY  - Cham
ER  - 
TY  - CHAP
A1  - Hüning, Felix
T1  - Sustainable changes beyond covid-19 for a second semester physics course for electrical engineering students
T2  - Blended Learning in Engineering Education: challenging, enlightening – and lasting?
N2  - The course Physics for Electrical Engineering is part of the curriculum of the bachelor program Electrical Engineering at University of Applied Science Aachen.
Before covid-19 the course was conducted in a rather traditional way with all parts (lecture, exercise and lab) face-to-face. This teaching approach changed fundamentally within a week when the covid-19 limitations forced all courses to distance learning. All parts of the course were transformed to pure distance learning including synchronous and asynchronous parts for the lecture, live online-sessions for the exercises and self-paced labs at home. Using these methods, the course was able to impart the required knowledge and competencies. Taking the teacher’s observations of the student’s learning behaviour and engagement, the formal and informal feedback of the students and the results of the exams into account, the new methods are evaluated with respect to effectiveness, sustainability and suitability for competence transfer. Based on this analysis strong and weak points of the concept and countermeasures to solve the weak points were identified. The analysis further leads to a sustainable teaching approach combining synchronous and asynchronous parts with self-paced learning times that can be used in a very flexible manner for different learning scenarios, pure online, hybrid (mixture of online and presence times) and pure presence teaching.
Y1  - 2021
SN  - 978-2-87352-023-6
N1  - SEFI 49th Annual Conference, Technische Universität Berlin (online), 13 – 16 September 2021
SP  - 1424
EP  - 1428
ER  - 
TY  - JOUR
A1  - Leise, Philipp
A1  - Eßer, Arved
A1  - Eichenlaub, Tobias
A1  - Schleiffer, Jean-Eric
A1  - Altherr, Lena
A1  - Rinderknecht, Stephan
A1  - Pelz, Peter F.
T1  - Sustainable system design of electric powertrains - comparison of optimization methods
JF  - Engineering Optimization
N2  - The transition within transportation towards battery electric vehicles can lead to a more sustainable future. To account for the development goal ‘climate action’ stated by the United Nations, it is mandatory, within the conceptual design phase, to derive energy-efficient system designs. One barrier is the uncertainty of the driving behaviour within the usage phase. This uncertainty is often addressed by using a stochastic synthesis process to derive representative driving cycles and by using cycle-based optimization. To deal with this uncertainty, a new approach based on a stochastic optimization program is presented. This leads to an optimization model that is solved with an exact solver. It is compared to a system design approach based on driving cycles and a genetic algorithm solver. Both approaches are applied to find efficient electric powertrains with fixed-speed and multi-speed transmissions. Hence, the similarities, differences and respective advantages of each optimization procedure are discussed.
KW  - Powertrain
KW  - stochastic optimization
KW  - global optimization
KW  - genetic algorithm
Y1  - 2021
U6  - https://doi.org/10.1080/0305215X.2021.1928660
SN  - 0305-215X
PB  - Taylor & Francis
CY  - London
ER  - 
TY  - CHAP
A1  - Leise, Philipp
A1  - Breuer, Tim
A1  - Altherr, Lena
A1  - Pelz, Peter F.
T1  - Development, validation and assessment of a resilient pumping system
T2  - Proceedings of the Joint International Resilience Conference, JIRC2020
N2  - The development of resilient technical systems is a challenging task, as the system should adapt automatically to unknown disturbances and component failures. To evaluate different approaches for deriving resilient technical system designs, we developed a modular test rig that is based on a pumping system. On the basis of this example
system, we present metrics to quantify resilience and an algorithmic approach to improve resilience. This approach enables the pumping system to automatically react on unknown disturbances and to reduce the impact of component failures. In this case, the system is able to automatically adapt its topology by activating additional valves. This enables the system to still reach a minimum performance, even in case of failures. Furthermore, timedependent disturbances are evaluated continuously, deviations from the original state are automatically detected and anticipated in the future. This allows to reduce the impact of future disturbances and leads to a more resilient
system behaviour.
KW  - water supply system
KW  - fault detection
KW  - anticipation strategy
Y1  - 2020
SN  - 978-90-365-5095-6
N1  - Joint International Resilience Conference 2020. Interconnected: Resilience Innovations for Sustainable Development Goals. 23 - 27 November, 2020, Singapore
SP  - 97
EP  - 100
ER  - 
TY  - CHAP
A1  - Lorenz, Imke-Sophie B.
A1  - Altherr, Lena
A1  - Pelz, Peter F.
T1  - Graph-theoretic resilience analysis of a water distribution system's topology
T2  - World Congress on Resilience, Reliability and Asset Management 2019
N2  - Water suppliers are faced with the great challenge of achieving high-quality and, at the same time, low-cost water supply. In practice, the focus is set on the most beneficial maintenance measures and/or capacity adaptations of existing water distribution systems (WDS). Since climatic and demographic influences will pose further challenges in the future, the resilience enhancement of WDS, i.e. the enhancement of their capability to withstand and recover from disturbances, has been in particular focus recently. To assess the resilience of WDS, metrics based on graph theory have been proposed. In this study, a promising approach is applied to assess the resilience of the WDS for a district in a major German City. The conducted analysis provides insight into the process of actively influencing the
resilience of WDS
KW  - Resilience Assessment
KW  - Graph Theory
KW  - Water Supply System
KW  - Case Study
Y1  - 2019
N1  - World Congress on Resilience, Reliability and Asset Management, 28-31 July 2019. Furama Riverfront Hotel, Singapore
SP  - 106
EP  - 109
ER  - 
TY  - JOUR
A1  - Altherr, Lena
A1  - Ederer, Thorsten
A1  - Lorenz, Ulf
A1  - Pelz, Peter F.
A1  - Pöttgen, Philipp
ED  - Lübbecke, Marco
ED  - Koster, Arie
ED  - Letmathe, Peter
ED  - Madlener, Reihard
ED  - Peis, Britta
ED  - Walther, Grit
T1  - Experimental validation of an enhanced system synthesis approach
JF  - Operations Research Proceedings 2014
N2  - Planning the layout and operation of a technical system is a common task
for an engineer. Typically, the workflow is divided into consecutive stages: First,
the engineer designs the layout of the system, with the help of his experience or of
heuristic methods. Secondly, he finds a control strategy which is often optimized
by simulation. This usually results in a good operating of an unquestioned sys-
tem topology. In contrast, we apply Operations Research (OR) methods to find a
cost-optimal solution for both stages simultaneously via mixed integer program-
ming (MILP). Technical Operations Research (TOR) allows one to find a provable
global optimal solution within the model formulation. However, the modeling error
due to the abstraction of physical reality remains unknown. We address this ubiq-
uitous problem of OR methods by comparing our computational results with mea-
surements in a test rig. For a practical test case we compute a topology and control
strategy via MILP and verify that the objectives are met up to a deviation of 8.7%.
Y1  - 2014
SN  - 978-3-319-28695-2
U6  - https://doi.org/10.1007/978-3-319-28697-6_1
PB  - Springer
CY  - Basel
ER  - 
TY  - JOUR
A1  - Sun, Hui
A1  - Altherr, Lena
A1  - Pei, Ji
A1  - Pelz, Peter F.
A1  - Yuan, Shouqi
T1  - Optimal booster station design and operation under uncertain load
JF  - Applied Mechanics and Materials
N2  - Given industrial applications, the costs for the operation and maintenance of a pump system typically far exceed its purchase price. For finding an optimal pump configuration which minimizes not only investment, but life-cycle costs, methods like Technical Operations Research which is based on Mixed-Integer Programming can be applied. However, during the planning phase, the designer is often faced with uncertain input data, e.g. future load demands can only be estimated. In this work, we deal with this uncertainty by developing a chance-constrained two-stage (CCTS) stochastic program. The design and operation of a booster station working under uncertain load demand are optimized to minimize total cost including purchase price, operation cost incurred by energy consumption and penalty cost resulting from water shortage. We find optimized system layouts using a sample average approximation (SAA) algorithm, and analyze the results for different risk levels of water shortage. By adjusting the risk level, the costs and performance range of the system can be balanced, and thus the
system’s resilience can be engineered
KW  - Stochastic Programming
KW  - Chance Constraint
KW  - Engineering Application
KW  - Pump System
KW  - Water Distribution
Y1  - 2018
U6  - https://doi.org/10.4028/www.scientific.net/AMM.885.102
SN  - 1662-7482
VL  - 885
SP  - 102
EP  - 115
PB  - Trans Tech Publications
CY  - Bäch
ER  - 
TY  - CHAP
A1  - Leise, Philipp
A1  - Altherr, Lena
T1  - Optimizing the design and control of decentralized water supply systems – a case-study of a hotel building
T2  - EngOpt 2018 Proceedings of the 6th International Conference on Engineering Optimization
N2  - To increase pressure to supply all floors of high buildings with water, booster stations, normally consisting of several parallel pumps in the basement, are used. In this work, we demonstrate the potential of a decentralized pump topology regarding energy savings in water supply systems of skyscrapers. We present an approach, based on Mixed-Integer Nonlinear Programming, that allows to choose an optimal network topology and optimal pumps from a predefined construction kit comprising different pump types. Using domain-specific scaling laws and Latin Hypercube Sampling, we generate different input sets of pump types and compare their impact on the efficiency and cost of the total system design. As a realistic application example, we consider a hotel building with 325 rooms, 12 floors and up to four pressure zones.
KW  - Engineering optimization
KW  - Energy efficiency
KW  - Water
KW  - Pump System
KW  - Latin Hypercube Sampling
Y1  - 2018
SN  - 978-3-319-97773-7
SN  - 978-3-319-97772-0
U6  - https://doi.org/10.1007/978-3-319-97773-7_107
N1  - EngOpt 2018 Proceedings of the 6th International Conference on Engineering Optimization. 17-19 September 2018. Lisboa, Portugal
SP  - 1241
EP  - 1252
PB  - Springer
CY  - Cham
ER  - 
TY  - CHAP
A1  - Stenger, David
A1  - Altherr, Lena
A1  - Müller, Tankred
A1  - Pelz, Peter F.
T1  - Product family design optimization using model-based engineering techniques
T2  - Operations Research Proceedings 2017
N2  - Highly competitive markets paired with tremendous production volumes demand particularly cost efficient products. The usage of common parts and modules across product families can potentially reduce production costs. Yet, increasing commonality typically results in overdesign of individual products. Multi domain virtual prototyping enables designers to evaluate costs and technical feasibility of different single product designs at reasonable computational effort in early design phases. However, savings by platform commonality are hard to quantify and require detailed knowledge of e.g. the production process and the supply chain. Therefore, we present and evaluate a multi-objective metamodel-based optimization algorithm which enables designers to explore the trade-off between high commonality and cost optimal design of single products.
Y1  - 2018
SN  - 978-3-319-89919-0
U6  - https://doi.org/10.1007/978-3-319-89920-6_66
SP  - 495
EP  - 502
PB  - Springer
CY  - Cham
ER  - 
TY  - JOUR
A1  - Altherr, Lena
A1  - Brötz, Nicolas
A1  - Dietrich, Ingo
A1  - Gally, Tristan
A1  - Geßner, Felix
A1  - Kloberdanz, Hermann
A1  - Leise, Philipp
A1  - Pelz, Peter Franz
A1  - Schlemmer, Pia
A1  - Schmitt, Andreas
T1  - Resilience in mechanical engineering - a concept for controlling uncertainty during design, production and usage phase of load-carrying structures
JF  - Applied Mechanics and Materials
N2  - Resilience as a concept has found its way into different disciplines to describe the ability of an individual or system to withstand and adapt to changes in its environment. In this paper, we provide an overview of the concept in different communities and extend it to the area of mechanical engineering. Furthermore, we present metrics to measure resilience in technical systems and illustrate them by applying them to load-carrying structures. By giving application examples from the Collaborative Research Centre (CRC) 805, we show how the concept of resilience can be used to control uncertainty during different stages of product life.
Y1  - 2018
SN  - 1662-7482
U6  - https://doi.org/10.4028/www.scientific.net/AMM.885.187
VL  - 885
SP  - 187
EP  - 198
PB  - Trans Tech Publications
CY  - Bäch
ER  - 
TY  - CHAP
A1  - Leise, Philipp
A1  - Altherr, Lena
A1  - Pelz, Peter F.
T1  - Technical Operations Research (TOR) - Algorithms, not Engineers, Design Optimal Energy Efficient and Resilient Cooling Systems
T2  - FAN2018 - Proceedings of the International Conference on Fan Noise, Aerodynamics, Applications and Systems
N2  - The overall energy efficiency of ventilation systems can be improved by considering not only single components, but by considering as well the interplay between every part of the system. With the help of the method "TOR" ("Technical Operations Research"), which was developed at the Chair of Fluid Systems at TU Darmstadt, it is possible to improve the energy efficiency of the whole system by considering all possible design choices programmatically. We show the ability of this systematic design approach with a ventilation system for buildings as a use case example.
Based on a Mixed-Integer Nonlinear Program (MINLP) we model the ventilation system. We use binary variables to model the selection of different pipe diameters. Multiple fans are model with the help of scaling laws. The whole system is represented by a graph, where the edges represent the pipes and fans and the nodes represents the source of air for cooling and the sinks, that have to be cooled. At the beginning, the human designer chooses a construction kit of different suitable fans and pipes of different diameters and different load cases. These boundary conditions define a variety of different possible system topologies. It is not possible to consider all topologies by hand. With the help of state of the art solvers, on the other side, it is possible to solve this MINLP.
Next to this, we also consider the effects of malfunctions in different components. Therefore, we show a first approach to measure the resilience of the shown example use case. Further, we compare the conventional approach with designs that are more resilient. These more resilient designs are derived by extending the before mentioned model with further constraints, that consider explicitly the resilience of the overall system. We show that it is possible to design resilient systems with this method already in the early design stage and compare the energy efficiency and resilience of these different system designs.
Y1  - 2018
N1  - International Conference on Fan Noise, Aerodynamics, Applications and Systems 
18-20.04.2018
Darmstadt, Deutschland
SP  - 1
EP  - 12
ER  - 
TY  - CHAP
A1  - Altherr, Lena
A1  - Dörig, Bastian
A1  - Ederer, Thorsten
A1  - Pelz, Peter Franz
A1  - Pfetsch, Marc
A1  - Wolf, Jan
T1  - A mixed-integer nonlinear program for the design of gearboxes
T2  - Operations Research Proceedings 2016
N2  - Gearboxes are mechanical transmission systems that provide speed and torque conversions from a rotating power source. Being a central element of the drive train, they are relevant for the efficiency and durability of motor vehicles. In this work, we present a new approach for gearbox design: Modeling the design problem as a mixed-integer nonlinear program (MINLP) allows us to create gearbox designs from scratch for arbitrary requirements and—given enough time—to compute provably globally optimal designs for a given objective. We show how different degrees of freedom influence the runtime and present an exemplary solution.
Y1  - 2017
SN  - 978-3-319-55701-4
U6  - https://doi.org/10.1007/978-3-319-55702-1_31
SP  - 227
EP  - 233
PB  - Springer
CY  - Cham
ER  - 
TY  - CHAP
A1  - Leise, Philipp
A1  - Altherr, Lena
A1  - Pelz, Peter F.
T1  - Energy-Efficient design of a water supply system for skyscrapers by mixed-integer nonlinear programming
T2  - Operations Research Proceedings 2017
N2  - The energy-efficiency of technical systems can be improved by a systematic design approach. Technical Operations Research (TOR) employs methods known from Operations Research to find a global optimal layout and operation strategy of technical systems. We show the practical usage of this approach by the systematic design of a decentralized water supply system for skyscrapers. All possible network options and operation strategies are modeled by a Mixed-Integer Nonlinear Program. We present the optimal system found by our approach and highlight the energy savings compared to a conventional system design.
KW  - Engineering optimization
KW  - Global optimization
KW  - Energy efficiency
KW  - Water
KW  - Network
Y1  - 2018
SN  - 978-3-319-89919-0
U6  - https://doi.org/10.1007/978-3-319-89920-6_63
PB  - Springer
CY  - Cham
ER  -