@article{AllefeldBialonski2007, author = {Allefeld, Carsten and Bialonski, Stephan}, title = {Detecting synchronization clusters in multivariate time series via coarse-graining of Markov chains}, series = {Physical Review E}, volume = {76}, journal = {Physical Review E}, number = {6}, issn = {2470-0053}, doi = {10.1103/PhysRevE.76.066207}, pages = {066207}, year = {2007}, language = {en} } @article{AlmajhdiSengerAmeretal.2014, author = {Almajhdi, Fahad N. and Senger, Tilo and Amer, Haitham M. and Gissmann, Lutz and {\"O}hlschl{\"a}ger, Peter}, title = {Design of a highly effective therapeutic HPV16 E6/E7-specific DNA vaccine: optimization by different ways of sequence rearrangements (Shuffling)}, series = {PLOS one}, volume = {11}, journal = {PLOS one}, number = {9}, publisher = {PLOS}, address = {San Francisco}, issn = {1932-6203}, doi = {10.1371/journal.pone.0113461}, pages = {e113461}, year = {2014}, abstract = {Persistent infection with the high-risk Human Papillomavirus type 16 (HPV 16) is the causative event for the development of cervical cancer and other malignant tumors of the anogenital tract and of the head and neck. Despite many attempts to develop therapeutic vaccines no candidate has entered late clinical trials. An interesting approach is a DNA based vaccine encompassing the nucleotide sequence of the E6 and E7 viral oncoproteins. Because both proteins are consistently expressed in HPV infected cells they represent excellent targets for immune therapy. Here we report the development of 8 DNA vaccine candidates consisting of differently rearranged HPV-16 E6 and E7 sequences within one molecule providing all naturally occurring epitopes but supposedly lacking transforming activity. The HPV sequences were fused to the J-domain and the SV40 enhancer in order to increase immune responses. We demonstrate that one out of the 8 vaccine candidates induces very strong cellular E6- and E7- specific cellular immune responses in mice and, as shown in regression experiments, efficiently controls growth of HPV 16 positive syngeneic tumors. This data demonstrates the potential of this vaccine candidate to control persistent HPV 16 infection that may lead to malignant disease. It also suggests that different sequence rearrangements influence the immunogenecity by an as yet unknown mechanism.}, language = {en} } @article{AlnemerKotliarNeuhausetal.2023, author = {Alnemer, Momin Sami Mohammad and Kotliar, Konstantin and Neuhaus, Valentin and Pape, Hans-Christoph and Ciritsis, Bernhard D.}, title = {Cost-effectiveness analysis of surgical proximal femur fracture prevention in elderly: a Markov cohort simulation model}, series = {Cost Effectiveness and Resource Allocation}, journal = {Cost Effectiveness and Resource Allocation}, number = {21, Article number: 77}, publisher = {Springer Nature}, issn = {1478-7547}, doi = {10.1186/s12962-023-00482-4}, pages = {12 Seiten}, year = {2023}, abstract = {Background Hip fractures are a common and costly health problem, resulting in significant morbidity and mortality, as well as high costs for healthcare systems, especially for the elderly. Implementing surgical preventive strategies has the potential to improve the quality of life and reduce the burden on healthcare resources, particularly in the long term. However, there are currently limited guidelines for standardizing hip fracture prophylaxis practices. Methods This study used a cost-effectiveness analysis with a finite-state Markov model and cohort simulation to evaluate the primary and secondary surgical prevention of hip fractures in the elderly. Patients aged 60 to 90 years were simulated in two different models (A and B) to assess prevention at different levels. Model A assumed prophylaxis was performed during the fracture operation on the contralateral side, while Model B included individuals with high fracture risk factors. Costs were obtained from the Centers for Medicare \& Medicaid Services, and transition probabilities and health state utilities were derived from available literature. The baseline assumption was a 10\% reduction in fracture risk after prophylaxis. A sensitivity analysis was also conducted to assess the reliability and variability of the results. Results With a 10\% fracture risk reduction, model A costs between \$8,850 and \$46,940 per quality-adjusted life-year (\$/QALY). Additionally, it proved most cost-effective in the age range between 61 and 81 years. The sensitivity analysis established that a reduction of ≥ 2.8\% is needed for prophylaxis to be definitely cost-effective. The cost-effectiveness at the secondary prevention level was most sensitive to the cost of the contralateral side's prophylaxis, the patient's age, and fracture treatment cost. For high-risk patients with no fracture history, the cost-effectiveness of a preventive strategy depends on their risk profile. In the baseline analysis, the incremental cost-effectiveness ratio at the primary prevention level varied between \$11,000/QALY and \$74,000/QALY, which is below the defined willingness to pay threshold. Conclusion Due to the high cost of hip fracture treatment and its increased morbidity, surgical prophylaxis strategies have demonstrated that they can significantly relieve the healthcare system. Various key assumptions facilitated the modeling, allowing for adequate room for uncertainty. Further research is needed to evaluate health-state-associated risks.}, language = {en} } @inproceedings{AltayButenwegKlinkel2013, author = {Altay, Okyay and Butenweg, Christoph and Klinkel, Sven}, title = {Vibration control of slender structures by semi-active tuned liquid column dampers}, series = {Conference of the ASCE Engineering Mechanics Institute , Evanston, IL , USA , EMI 2013 , 2013-08-04 - 2013-08-07}, booktitle = {Conference of the ASCE Engineering Mechanics Institute , Evanston, IL , USA , EMI 2013 , 2013-08-04 - 2013-08-07}, pages = {1 Seite}, year = {2013}, language = {en} } @inproceedings{AltayButenwegKlinkel2014, author = {Altay, Okyay and Butenweg, Christoph and Klinkel, Sven}, title = {Vibration mitigation of wind turbine towers by a new semiactive Tuned Liquid Column Damper}, series = {6. Word Congress on Structural Control and Monitoring, 15 - 17 July, 2014 Barcelona,Spain}, booktitle = {6. Word Congress on Structural Control and Monitoring, 15 - 17 July, 2014 Barcelona,Spain}, year = {2014}, language = {en} } @inproceedings{AltayButenwegKlinkeletal.2014, author = {Altay, Okyay and Butenweg, Christoph and Klinkel, Sven and Taddei, Francesca}, title = {Vibration mitigation of wind turbine towers by tuned liquid column dampers}, series = {Proceedings of the 9th European Conference on Structural Dynamics, EURODYN 2014 Porto, Portugal, 30 June - 2 July 2014 / A. Cunha, E. Caetano, .... (eds.)}, booktitle = {Proceedings of the 9th European Conference on Structural Dynamics, EURODYN 2014 Porto, Portugal, 30 June - 2 July 2014 / A. Cunha, E. Caetano, .... (eds.)}, address = {Porto}, organization = {European Conference on Structural Dynamics, EURODYN <9, 2014, Porto>}, isbn = {978-972-752-165-4}, pages = {1531 -- 1538}, year = {2014}, language = {en} } @incollection{AltayTaddeiButenwegetal.2014, author = {Altay, Okyay and Taddei, Francesca and Butenweg, Christoph and Klinkel, Sven}, title = {Vibration mitigation of wind turbine towers with tuned mass dampers}, series = {Wind turbine control and monitoring. (Advances in industrial control)}, booktitle = {Wind turbine control and monitoring. (Advances in industrial control)}, publisher = {Springer}, address = {Cham ; Heidelberg ; New York ; Dordrecht ; London}, isbn = {978-3-319-08412-1 (Print) ; 978-3-319-08413-8 (E-Book)}, doi = {10.1007/978-3-319-08413-8_12}, pages = {337 -- 373}, year = {2014}, abstract = {Because of its minor environmental impact, electricity generation using wind power is getting remarkable. The further growth of the wind industry depends on technological solutions to the challenges in production and construction of the turbines. Wind turbine tower vibrations, which limit power generation efficiency and cause fatigue problems with high maintenance costs, count as one of the main structural difficulties in the wind energy sector. To mitigate tower vibrations auxiliary measures are necessary. The effectiveness of tuned mass damper is verified by means of a numeric study on a 5 MW onshore reference wind turbine. Hereby, also seismic-induced vibrations and soil-structure interaction are considered. Acquired results show that tuned mass damper can effectively reduce resonant tower vibrations and improve the fatigue life of wind turbines. This chapter is also concerned with tuned liquid column damper and a semiactive application of it. Due to its geometric versatility and low prime costs, tuned liquid column dampers are a good alternative to other damping measures, in particular for slender structures like wind turbines.}, language = {en} } @book{Altherr2016, author = {Altherr, Lena}, title = {Algorithmic System Design under Consideration of Dynamic Processes}, publisher = {Shaker}, address = {Aachen}, isbn = {978-3-8440-4848-3}, pages = {94}, year = {2016}, abstract = {Nach Stand von Wissenschaft und Technik werden Komponenten hinsichtlich ihrer Eigenschaften, wie Lebensdauer oder Energieeffizienz, optimiert. Allerdings k{\"o}nnen selbst hervorragende Komponenten zu ineffizienten oder instabilen Systemen f{\"u}hren, wenn ihr Zusammenspiel nur unzureichend ber{\"u}cksichtigt wird. Eine Systembetrachtung schafft ein gr{\"o}ßeres Optimierungspotential - dem erh{\"o}hten Potential steht jedoch auch ein erh{\"o}hter Komplexit{\"a}tsgrad gegen{\"u}ber. Die vorliegende Arbeit ist im Rahmen des Sonderforschungsbereichs 805 entstanden, dessen Ziel die Beherrschung von Unsicherheit in Systemen des Maschinenbaus ist. Die Arbeit zeigt anhand eines realen Systems aus dem Bereich der Hydraulik, wie Unsicherheit in der Entwicklungsphase beherrscht werden kann. Hierbei ist neu, dass die durch den sp{\"a}teren Betrieb zu erwartende Systemdegradation eines jeden m{\"o}glichen Systemvorschlags antizipiert werden kann. Dadurch k{\"o}nnen Betriebs- und Wartungskosten vorausgesagt und minimiert werden und durch eine optimale Betriebs- und Wartungsstrategie die Verf{\"u}gbarkeit des Systems garantiert werden. Wesentliche Fragen bei der optimalen Auslegung des betrachteten hydrostatischen Getriebes sind dessen physikalische Modellierung, die Darstellung des Optimierungsproblems als gemischt-ganzzahliges lineares Programm, und dessen algorithmische Behandlung zur L{\"o}sungsfindung. Hierzu werden Heuristiken zum schnelleren Auffinden sinnvoller Systemtopologien vorgestellt und mittels mathematischer Dekomposition eine Bewertung des dynamischen Verschleiß- und Wartungsverlaufs m{\"o}glicher Systemvorschl{\"a}ge vorgenommen. Die Arbeit stellt die Optimierung technischer Systeme an der Schnittstelle von Mathematik, Informatik und Ingenieurwesen sowohl gr{\"u}ndlich als auch anschaulich und nachvollziehbar dar.}, language = {en} } @article{AltherrBroetzDietrichetal.2018, author = {Altherr, Lena and Br{\"o}tz, Nicolas and Dietrich, Ingo and Gally, Tristan and Geßner, Felix and Kloberdanz, Hermann and Leise, Philipp and Pelz, Peter Franz and Schlemmer, Pia and Schmitt, Andreas}, title = {Resilience in mechanical engineering - a concept for controlling uncertainty during design, production and usage phase of load-carrying structures}, series = {Applied Mechanics and Materials}, volume = {885}, journal = {Applied Mechanics and Materials}, publisher = {Trans Tech Publications}, address = {B{\"a}ch}, isbn = {1662-7482}, doi = {10.4028/www.scientific.net/AMM.885.187}, pages = {187 -- 198}, year = {2018}, abstract = {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.}, language = {en} } @inproceedings{AltherrConzenElsenetal.2023, author = {Altherr, Lena and Conzen, Max and Elsen, Ingo and Frauenrath, Tobias and Lyrmann, Andreas}, title = {Sensor retrofitting of existing buildings in an interdisciplinary teaching project at university level}, series = {Tagungsband AALE 2023 : mit Automatisierung gegen den Klimawandel}, booktitle = {Tagungsband AALE 2023 : mit Automatisierung gegen den Klimawandel}, editor = {Reiff-Stephan, J{\"o}rg and J{\"a}kel, Jens and Schwarz, Andr{\´e}}, publisher = {le-tex publishing services GmbH}, address = {Leipzig}, isbn = {978-3-910103-01-6}, doi = {10.33968/2023.04}, pages = {31 -- 40}, year = {2023}, abstract = {Existing residential buildings have an average lifetime of 100 years. Many of these buildings will exist for at least another 50 years. To increase the efficiency of these buildings while keeping costs at reasonable rates, they can be retrofitted with sensors that deliver information to central control units for heating, ventilation and electricity. This retrofitting process should happen with minimal intervention into existing infrastructure and requires new approaches for sensor design and data transmission. At FH Aachen University of Applied Sciences, students of different disciplines work together to learn how to design, build, deploy and operate such sensors. The presented teaching project already created a low power design for a combined CO2, temperature and humidity measurement device that can be easily integrated into most home automation systems}, language = {en} } @incollection{AltherrDoerigEdereretal.2017, author = {Altherr, Lena and D{\"o}rig, Bastian and Ederer, Thorsten and Pelz, Peter Franz and Pfetsch, Marc and Wolf, Jan}, title = {A mixed-integer nonlinear program for the design of gearboxes}, series = {Operations Research Proceedings 2016}, booktitle = {Operations Research Proceedings 2016}, publisher = {Springer}, address = {Cham}, isbn = {978-3-319-55701-4}, doi = {10.1007/978-3-319-55702-1_31}, pages = {227 -- 233}, year = {2017}, abstract = {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.}, language = {en} } @inproceedings{AltherrEdererFarnetaneetal.2017, author = {Altherr, Lena and Ederer, Thorsten and Farnetane, Lucas S. and P{\"o}ttgen, Philipp and Verg{\´e}, Angela and Pelz, Peter F.}, title = {Multicriterial design of a hydrostatic transmission system via mixed-integer programming}, series = {Operations Research Proceedings 2015}, booktitle = {Operations Research Proceedings 2015}, publisher = {Springer}, address = {Cham}, isbn = {978-3-319-42901-4}, doi = {10.1007/978-3-319-42902-1_41}, pages = {301 -- 307}, year = {2017}, abstract = {In times of planned obsolescence the demand for sustainability keeps growing. Ideally, a technical system is highly reliable, without failures and down times due to fast wear of single components. At the same time, maintenance should preferably be limited to pre-defined time intervals. Dispersion of load between multiple components can increase a system's reliability and thus its availability inbetween maintenance points. However, this also results in higher investment costs and additional efforts due to higher complexity. Given a specific load profile and resulting wear of components, it is often unclear which system structure is the optimal one. Technical Operations Research (TOR) finds an optimal structure balancing availability and effort. We present our approach by designing a hydrostatic transmission system.}, language = {en} } @incollection{AltherrEdererLorenzetal.2016, author = {Altherr, Lena and Ederer, Thorsten and Lorenz, Ulf and Pelz, Peter F. and P{\"o}ttgen, Philipp}, title = {Designing a feedback control system via mixed-integer programming}, series = {Operations Research Proceedings 2014: Selected Papers of the Annual International Conference of the German Operations Research}, booktitle = {Operations Research Proceedings 2014: Selected Papers of the Annual International Conference of the German Operations Research}, editor = {L{\"u}bbecke, Marco E. and Koster, Arie and Letmathe, Peter and Madlener, Reihard and Preis, Britta and Walther, Grit}, publisher = {Springer}, address = {Cham}, isbn = {978-3-319-28695-2}, doi = {10.1007/978-3-319-28697-6_18}, pages = {121 -- 127}, year = {2016}, abstract = {Pure analytical or experimental methods can only find a control strategy for technical systems with a fixed setup. In former contributions we presented an approach that simultaneously finds the optimal topology and the optimal open-loop control of a system via Mixed Integer Linear Programming (MILP). In order to extend this approach by a closed-loop control we present a Mixed Integer Program for a time discretized tank level control. This model is the basis for an extension by combinatorial decisions and thus for the variation of the network topology. Furthermore, one is able to appraise feasible solutions using the global optimality gap.}, language = {en} } @article{AltherrEdererLorenzetal.2014, author = {Altherr, Lena and Ederer, Thorsten and Lorenz, Ulf and Pelz, Peter F. and P{\"o}ttgen, Philipp}, title = {Experimental validation of an enhanced system synthesis approach}, series = {Operations Research Proceedings 2014}, journal = {Operations Research Proceedings 2014}, editor = {L{\"u}bbecke, Marco and Koster, Arie and Letmathe, Peter and Madlener, Reihard and Peis, Britta and Walther, Grit}, publisher = {Springer}, address = {Basel}, isbn = {978-3-319-28695-2}, doi = {10.1007/978-3-319-28697-6_1}, pages = {6}, year = {2014}, abstract = {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\%.}, language = {en} } @article{AltherrEdererPoettgenetal.2015, author = {Altherr, Lena and Ederer, Thorsten and P{\"o}ttgen, Philipp and Lorenz, Ulf and Pelz, Peter F.}, title = {Multicriterial optimization of technical systems considering multiple load and availability scenarios}, series = {Applied Mechanics and Materials}, volume = {807}, journal = {Applied Mechanics and Materials}, editor = {Pelz, Peter F. and Groche, Peter}, isbn = {1660-9336}, doi = {10.4028/www.scientific.net/AMM.807.247}, pages = {247 -- 256}, year = {2015}, abstract = {Cheap does not imply cost-effective -- this is rule number one of zeitgeisty system design. The initial investment accounts only for a small portion of the lifecycle costs of a technical system. In fluid systems, about ninety percent of the total costs are caused by other factors like power consumption and maintenance. With modern optimization methods, it is already possible to plan an optimal technical system considering multiple objectives. In this paper, we focus on an often neglected contribution to the lifecycle costs: downtime costs due to spontaneous failures. Consequently, availability becomes an issue.}, language = {en} } @inproceedings{AltherrEdererSchaenzleetal.2017, author = {Altherr, Lena and Ederer, Thorsten and Sch{\"a}nzle, Christian and Lorenz, Ulf and Pelz, Peter F.}, title = {Algorithmic system design using scaling and affinity laws}, series = {Operations Research Proceedings 2015}, booktitle = {Operations Research Proceedings 2015}, publisher = {Springer}, address = {Cham}, isbn = {978-3-319-42901-4}, doi = {10.1007/978-3-319-42902-1}, pages = {605 -- 611}, year = {2017}, abstract = {Energy-efficient components do not automatically lead to energy-efficient systems. Technical Operations Research (TOR) shifts the focus from the single component to the system as a whole and finds its optimal topology and operating strategy simultaneously. In previous works, we provided a preselected construction kit of suitable components for the algorithm. This approach may give rise to a combinatorial explosion if the preselection cannot be cut down to a reasonable number by human intuition. To reduce the number of discrete decisions, we integrate laws derived from similarity theory into the optimization model. Since the physical characteristics of a production series are similar, it can be described by affinity and scaling laws. Making use of these laws, our construction kit can be modeled more efficiently: Instead of a preselection of components, it now encompasses whole model ranges. This allows us to significantly increase the number of possible set-ups in our model. In this paper, we present how to embed this new formulation into a mixed-integer program and assess the run time via benchmarks. We present our approach on the example of a ventilation system design problem.}, language = {en} } @article{AltherrJoggerstLeiseetal.2018, author = {Altherr, Lena and Joggerst, Laura and Leise, Philipp and Pfetsch, Marc E. and Schmitt, Andreas and Wendt, Janine}, title = {On obligations in the development process of resilient systems with algorithmic design methods}, series = {Applied Mechanics and Materials}, volume = {885}, journal = {Applied Mechanics and Materials}, number = {885}, publisher = {Trans Tech Publications}, address = {B{\"a}ch}, isbn = {1662-7482}, doi = {10.4028/www.scientific.net/AMM.885.240}, pages = {240 -- 252}, year = {2018}, abstract = {Advanced computational methods are needed both for the design of large systems and to compute high accuracy solutions. Such methods are efficient in computation, but the validation of results is very complex, and highly skilled auditors are needed to verify them. We investigate legal questions concerning obligations in the development phase, especially for technical systems developed using advanced methods. In particular, we consider methods of resilient and robust optimization. With these techniques, high performance solutions can be found, despite a high variety of input parameters. However, given the novelty of these methods, it is uncertain whether legal obligations are being met. The aim of this paper is to discuss if and how the choice of a specific computational method affects the developer's product liability. The review of legal obligations in this paper is based on German law and focuses on the requirements that must be met during the design and development process.}, language = {en} } @incollection{AltherrLeise2021, author = {Altherr, Lena and Leise, Philipp}, title = {Resilience as a concept for mastering uncertainty}, series = {Mastering Uncertainty in Mechanical Engineering}, booktitle = {Mastering Uncertainty in Mechanical Engineering}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-78353-2}, doi = {10.1007/978-3-030-78354-9}, pages = {412 -- 417}, year = {2021}, language = {en} } @article{AltherrLeisePfetschetal.2018, author = {Altherr, Lena and Leise, Philipp and Pfetsch, Marc E. and Schmitt, Andreas}, title = {Algorithmic design and resilience assessment of energy efficient high-rise water supply systems}, series = {Applied Mechanics and Materials}, volume = {885}, journal = {Applied Mechanics and Materials}, publisher = {Trans Tech Publications}, address = {B{\"a}ch}, issn = {1662-7482}, doi = {10.4028/www.scientific.net/AMM.885.211}, pages = {211 -- 223}, year = {2018}, abstract = {High-rise water supply systems provide water flow and suitable pressure in all levels of tall buildings. To design such state-of-the-art systems, the consideration of energy efficiency and the anticipation of component failures are mandatory. In this paper, we use Mixed-Integer Nonlinear Programming to compute an optimal placement of pipes and pumps, as well as an optimal control strategy.Moreover, we consider the resilience of the system to pump failures. A resilient system is able to fulfill a predefined minimum functionality even though components fail or are restricted in their normal usage. We present models to measure and optimize the resilience. To demonstrate our approach, we design and analyze an optimal resilient decentralized water supply system inspired by a real-life hotel building.}, language = {en} } @incollection{AltherrLeisePfetschetal.2021, author = {Altherr, Lena and Leise, Philipp and Pfetsch, Marc E. and Schmitt, Andreas}, title = {Optimal design of resilient technical systems on the example of water supply systems}, series = {Mastering Uncertainty in Mechanical Engineering}, booktitle = {Mastering Uncertainty in Mechanical Engineering}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-78356-3}, pages = {429 -- 433}, year = {2021}, language = {en} }