@incollection{BorggrafeOhndorfDachwaldetal.2012, author = {Borggrafe, Andreas and Ohndorf, Andreas and Dachwald, Bernd and Seboldt, Wolfgang}, title = {Analysis of interplanetary solar sail trajectories with attitude dynamics}, series = {Dynamics and Control of Space Systems 2012}, booktitle = {Dynamics and Control of Space Systems 2012}, publisher = {Univelt Inc}, address = {San Diego}, isbn = {978-0-87703-587-9}, pages = {1553 -- 1569}, year = {2012}, abstract = {We present a new approach to the problem of optimal control of solar sails for low-thrust trajectory optimization. The objective was to find the required control torque magnitudes in order to steer a solar sail in interplanetary space. A new steering strategy, controlling the solar sail with generic torques applied about the spacecraft body axes, is integrated into the existing low-thrust trajectory optimization software InTrance. This software combines artificial neural networks and evolutionary algorithms to find steering strategies close to the global optimum without an initial guess. Furthermore, we implement a three rotational degree-of-freedom rigid-body attitude dynamics model to represent the solar sail in space. Two interplanetary transfers to Mars and Neptune are chosen to represent typical future solar sail mission scenarios. The results found with the new steering strategy are compared to the existing reference trajectories without attitude dynamics. The resulting control torques required to accomplish the missions are investigated, as they pose the primary requirements to a real on-board attitude control system.}, language = {en} } @article{LeversStaatLaack2011, author = {Levers, A. and Staat, Manfred and Laack, Walter van}, title = {Analyse der Langzeitwirkung der MBST® KernspinResonanzTherapie bei Gonarthrose}, year = {2011}, abstract = {Originalausgabe: Orthop{\"a}dische Praxis Jg. 47. 2011 H. 11; S. 536-543. Mit freundlicher Genehmigung des Verlags Zusammenfassung: Auf der Basis von Patientenabfragen mittels Fragebogen zum Schmerzempfinden und zur Einschr{\"a}nkung bei Aktivit{\"a}ten des allt{\"a}glichen Lebens wird die Langzeitwirkung der MBST® KernspinResonanz-Therapie bei Gonarthrose untersucht. An der Studie nahmen 39 Patienten teil, bei denen die Therapie bis zu vier Jahre zur{\"u}ckliegt. Neben einer Gesamtbetrachtung wird der Erfolg auch in Abh{\"a}ngigkeit von Alter, Geschlecht und sportlicher Aktivit{\"a}t analysiert. Insgesamt weist die Studie auf eine anhaltende Verbesserung des Gesundheitszustands mit zum Teil deutlicher Schmerzlinderung auch noch nach vier Jahren hin, jedoch mit einer leichten Schmerzzunahme gegen Ende des Untersuchungszeitraums von vier Jahren. Eine tendenziell positivere Wirkung bei Frauen, {\"a}lteren Menschen oder auch sportlich nicht-aktiven Patienten l{\"a}sst auf eine m{\"o}gliche Beeinflussung des Erfolgs der Therapie durch ({\"U}ber-)Belastung im Alltag schließen. Ein zus{\"a}tzlich positiver Effekt der Therapie auf die Knochendichte ist ebenfalls denkbar, dies bleibt jedoch offen.}, subject = {Kniegelenkarthrose}, language = {de} } @article{PhamStaat2013, author = {Pham, Phu Tinh and Staat, Manfred}, title = {An Upper Bound Algorithm for Limit and Shakedown Analysis of Bounded Linearly Kinematic Hardening Structures}, series = {Limit State of Materials and Structures : Direct Methods 2. Saxc{\´e}, G{\´e}ry de (Hrsg.)}, journal = {Limit State of Materials and Structures : Direct Methods 2. Saxc{\´e}, G{\´e}ry de (Hrsg.)}, publisher = {Springer}, address = {Dordrecht}, isbn = {978-94-007-5424-9}, pages = {71 -- 87}, year = {2013}, language = {en} } @article{AbelKahmannMellonetal.2020, author = {Abel, Alexander and Kahmann, Stephanie Lucina and Mellon, Stephen and Staat, Manfred and Jung, Alexander}, title = {An open-source tool for the validation of finite element models using three-dimensional full-field measurements}, series = {Medical Engineering \& Physics}, volume = {77}, journal = {Medical Engineering \& Physics}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1350-4533}, doi = {10.1016/j.medengphy.2019.10.015}, pages = {125 -- 129}, year = {2020}, abstract = {Three-dimensional (3D) full-field measurements provide a comprehensive and accurate validation of finite element (FE) models. For the validation, the result of the model and measurements are compared based on two respective point-sets and this requires the point-sets to be registered in one coordinate system. Point-set registration is a non-convex optimization problem that has widely been solved by the ordinary iterative closest point algorithm. However, this approach necessitates a good initialization without which it easily returns a local optimum, i.e. an erroneous registration. The globally optimal iterative closest point (Go-ICP) algorithm has overcome this drawback and forms the basis for the presented open-source tool that can be used for the validation of FE models using 3D full-field measurements. The capability of the tool is demonstrated using an application example from the field of biomechanics. Methodological problems that arise in real-world data and the respective implemented solution approaches are discussed.}, language = {en} } @inproceedings{LoebSchartnerDachwaldetal.2011, author = {Loeb, Horst W. and Schartner, Karl-Heinz and Dachwald, Bernd and Ohndorf, Andreas and Seboldt, Wolfgang}, title = {An Interstellar - Heliopause mission using a combination of solar/radioisotope electric propulsion}, series = {Presented at the 32nd International Electric Propulsion Conference}, booktitle = {Presented at the 32nd International Electric Propulsion Conference}, pages = {1 -- 7}, year = {2011}, abstract = {There is common agreement within the scientific community that in order to understand our local galactic environment it will be necessary to send a spacecraft into the region beyond the solar wind termination shock. Considering distances of 200 AU for a new mission, one needs a spacecraft travelling at a speed of close to 10 AU/yr in order to keep the mission duration in the range of less than 25 yrs, a transfer time postulated by ESA.Two propulsion options for the mission have been proposed and discussed so far: the solar sail propulsion and the ballistic/radioisotope electric propulsion. As a further alternative, we here investigate a combination of solar-electric propulsion and radioisotope-electric propulsion. The solar-electric propulsion stage consists of six 22 cm diameter "RIT-22"ion thrusters working with a high specific impulse of 7377 s corresponding to a positive grid voltage of 5 kV. Solar power of 53 kW BOM is provided by a light-weight solar array. The REP-stage consists of four space-proven 10 cm diameter "RIT-10" ion thrusters that will be operating one after the other for 9 yrs in total. Four advanced radioisotope generators provide 648 W at BOM. The scientific instrument package is oriented at earlier studies. For its mass and electric power requirement 35 kg and 35 W are assessed, respectively. Optimized trajectory calculations, treated in a separate contribution, are based on our "InTrance" method.The program yields a burn out of the REP stage in a distance of 79.6 AU for a usage of 154 kg of Xe propellant. With a C3 = 45,1 (km/s)2 a heliocentric probe velocity of 10 AU/yr is reached at this distance, provided a close Jupiter gravity assist adds a velocity increment of 2.7 AU/yr. A transfer time of 23.8 yrs results for this scenario requiring about 450 kg Xe for the SEP stage, jettisoned at 3 AU. We interpret the SEP/REP propulsion as a competing alternative to solar sail and ballistic/REP propulsion. Omiting a Jupiter fly-by even allows more launch flexibility, leaving the mission duration in the range of the ESA specification.}, language = {en} } @article{StaatKuehnHaugeretal.2004, author = {Staat, Manfred and K{\"u}hn, R. and Hauger, W. and Sponagel, Stefan}, title = {An Interpretation of Wolff's Law}, series = {Biomedizinische Technik. 49 (2004)}, journal = {Biomedizinische Technik. 49 (2004)}, isbn = {0932-4666}, pages = {1020 -- 1021}, year = {2004}, language = {de} } @article{Staat2021, author = {Staat, Manfred}, title = {An extension strain type Mohr-Coulomb criterion}, series = {Rock mechanics and rock engineering}, volume = {54}, journal = {Rock mechanics and rock engineering}, number = {12}, publisher = {Springer Nature}, address = {Cham}, issn = {1434-453X}, doi = {10.1007/s00603-021-02608-7}, pages = {6207 -- 6233}, year = {2021}, abstract = {Extension fractures are typical for the deformation under low or no confining pressure. They can be explained by a phenomenological extension strain failure criterion. In the past, a simple empirical criterion for fracture initiation in brittle rock has been developed. In this article, it is shown that the simple extension strain criterion makes unrealistic strength predictions in biaxial compression and tension. To overcome this major limitation, a new extension strain criterion is proposed by adding a weighted principal shear component to the simple criterion. The shear weight is chosen, such that the enriched extension strain criterion represents the same failure surface as the Mohr-Coulomb (MC) criterion. Thus, the MC criterion has been derived as an extension strain criterion predicting extension failure modes, which are unexpected in the classical understanding of the failure of cohesive-frictional materials. In progressive damage of rock, the most likely fracture direction is orthogonal to the maximum extension strain leading to dilatancy. The enriched extension strain criterion is proposed as a threshold surface for crack initiation CI and crack damage CD and as a failure surface at peak stress CP. Different from compressive loading, tensile loading requires only a limited number of critical cracks to cause failure. Therefore, for tensile stresses, the failure criteria must be modified somehow, possibly by a cut-off corresponding to the CI stress. Examples show that the enriched extension strain criterion predicts much lower volumes of damaged rock mass compared to the simple extension strain criterion.}, language = {en} } @inproceedings{Behbahani2014, author = {Behbahani, Mehdi}, title = {An Experimental Study of Thrombocyte Reactions in Response to Biomaterial Surfaces and Varying Shear Stress}, series = {Proceedings of the International Conference on Biomedical Engineering and Systems Prague, Czech Republic, August 14-15, 2014}, booktitle = {Proceedings of the International Conference on Biomedical Engineering and Systems Prague, Czech Republic, August 14-15, 2014}, pages = {Paper 125}, year = {2014}, language = {en} } @article{TranMottaghyArltKoerferetal.2017, author = {Tran, Linda and Mottaghy, K. and Arlt-K{\"o}rfer, Sabine and Waluga, Christian and Behbahani, Mehdi}, title = {An experimental study of shear-dependent human platelet adhesion and underlying protein-binding mechanisms in a cylindrical Couette system}, series = {Biomedizinische Technik}, volume = {62}, journal = {Biomedizinische Technik}, number = {4}, publisher = {De Gruyter}, address = {Berlin}, issn = {0013-5585}, doi = {10.1515/bmt-2015-0034}, pages = {383 -- 392}, year = {2017}, language = {en} } @article{NiedermeyerZhouDursunetal.2016, author = {Niedermeyer, Angela and Zhou, Bei and Dursun, G{\"o}zde and Temiz Artmann, Ayseg{\"u}l and Markert, Bernd}, title = {An examination of tissue engineered scaffolds in a bioreactor}, series = {Proceedings in Applied Mathematics and Mechanics PAMM}, volume = {16}, journal = {Proceedings in Applied Mathematics and Mechanics PAMM}, number = {1}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1617-7061}, doi = {10.1002/pamm.201610038}, pages = {99 -- 100}, year = {2016}, abstract = {Replacement tissues, designed to fill in articular cartilage defects, should exhibit the same properties as the native material. The aim of this study is to foster the understanding of, firstly, the mechanical behavior of the material itself and, secondly, the influence of cultivation parameters on cell seeded implants as well as on cell migration into acellular implants. In this study, acellular cartilage replacement material is theoretically, numerically and experimentally investigated regarding its viscoelastic properties, where a phenomenological model for practical applications is developed. Furthermore, remodeling and cell migration are investigated.}, language = {en} } @article{ColomboDriraFrotscheretal.2022, author = {Colombo, Daniele and Drira, Slah and Frotscher, Ralf and Staat, Manfred}, title = {An element-based formulation for ES-FEM and FS-FEM models for implementation in standard solid mechanics finite element codes for 2D and 3D static analysis}, series = {International Journal for Numerical Methods in Engineering}, volume = {124}, journal = {International Journal for Numerical Methods in Engineering}, number = {2}, publisher = {Wiley}, address = {Chichester}, issn = {1097-0207}, doi = {10.1002/nme.7126}, pages = {402 -- 433}, year = {2022}, abstract = {Edge-based and face-based smoothed finite element methods (ES-FEM and FS-FEM, respectively) are modified versions of the finite element method allowing to achieve more accurate results and to reduce sensitivity to mesh distortion, at least for linear elements. These properties make the two methods very attractive. However, their implementation in a standard finite element code is nontrivial because it requires heavy and extensive modifications to the code architecture. In this article, we present an element-based formulation of ES-FEM and FS-FEM methods allowing to implement the two methods in a standard finite element code with no modifications to its architecture. Moreover, the element-based formulation permits to easily manage any type of element, especially in 3D models where, to the best of the authors' knowledge, only tetrahedral elements are used in FS-FEM applications found in the literature. Shape functions for non-simplex 3D elements are proposed in order to apply FS-FEM to any standard finite element.}, language = {en} } @inproceedings{FrotscherStaat2015, author = {Frotscher, Ralf and Staat, Manfred}, title = {An electromechanical model for cardiac tissue constructs}, series = {Conference proceedings of the YIC GACM 2015 : 3rd ECCOMAS Young Investigators Conference and 6th GACM Colloquium on Computational Mechanics , Aachen, 20.07.2015 - 23.07.2015 / ed.: Stefanie Elgeti ; Jaan-Willem Simon}, booktitle = {Conference proceedings of the YIC GACM 2015 : 3rd ECCOMAS Young Investigators Conference and 6th GACM Colloquium on Computational Mechanics , Aachen, 20.07.2015 - 23.07.2015 / ed.: Stefanie Elgeti ; Jaan-Willem Simon}, publisher = {RWTH Aachen University}, address = {Aachen}, organization = {ECCOMAS Young Investigators Conference <3, 2015, Aachen>}, pages = {1 -- 4}, year = {2015}, language = {en} } @article{TranStaat2013, author = {Tran, Thanh Ngoc and Staat, Manfred}, title = {An Edge-Based Smoothed Finite Element Method for Primal-Dual Shakedown Analysis of Structures Under Uncertainties}, series = {Limit State of Materials and Structures : Direct Methods 2. Saxc{\´e}, G{\´e}ry de (Hrsg.)}, journal = {Limit State of Materials and Structures : Direct Methods 2. Saxc{\´e}, G{\´e}ry de (Hrsg.)}, publisher = {Springer}, address = {Dordrecht}, isbn = {978-94-007-5424-9}, pages = {89 -- 102}, year = {2013}, language = {en} } @article{VuStaat2004, author = {Vu, Duc-Khoi and Staat, Manfred}, title = {An algorithm for shakedown analysis of structure with temperature dependent yield stress}, year = {2004}, abstract = {This work is an attempt to answer the question: How to use convex programming in shakedown analysis of structures made of materials with temperature-dependent properties. Based on recently established shakedown theorems and formulations, a dual relationship between upper and lower bounds of the shakedown limit load is found, an algorithmfor shakedown analysis is proposed. While the original problem is neither convex nor concave, the algorithm presented here has the advantage of employing convex programming tools.}, subject = {Einspielen }, language = {en} } @article{StaatVu2004, author = {Staat, Manfred and Vu, Duc-Khoi}, title = {An Algorithm for Shakedown Analysis for Materials with Temperature Dependent Yield Stress}, series = {Proceedings in Applied Mathematics and Mechanics (PAMM). 4 (2004), H. 1}, journal = {Proceedings in Applied Mathematics and Mechanics (PAMM). 4 (2004), H. 1}, isbn = {1617-7061}, pages = {231 -- 233}, year = {2004}, language = {en} } @article{SchaelAtanasyanBerdugoetal.2019, author = {Schael, S. and Atanasyan, A. and Berdugo, J. and Bretz, T. and Czupalla, Markus and Dachwald, Bernd and Doetinchem, P. von and Duranti, M. and Gast, H. and Karpinski, W. and Kirn, T. and L{\"u}belsmeyer, K. and Ma{\~n}a, C. and Marrocchesi, P.S. and Mertsch, P. and Moskalenko, I.V. and Schervan, T. and Schluse, M. and Schr{\"o}der, K.-U. and Schultz von Dratzig, A. and Senatore, C. and Spies, L. and Wakely, S.P. and Wlochal, M. and Uglietti, D. and Zimmermann, J.}, title = {AMS-100: The next generation magnetic spectrometer in space - An international science platform for physics and astrophysics at Lagrange point 2}, series = {Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, volume = {944}, journal = {Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, number = {162561}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0168-9002}, doi = {10.1016/j.nima.2019.162561}, year = {2019}, language = {en} } @article{KotliarOrtnerConradietal.2022, author = {Kotliar, Konstantin and Ortner, Marion and Conradi, Anna and Hacker, Patricia and Hauser, Christine and G{\"u}nthner, Roman and Moser, Michaela and Muggenthaler, Claudia and Diehl-Schmid, Janine and Priller, Josef and Schmaderer, Christoph and Grimmer, Timo}, title = {Altered retinal cerebral vessel oscillation frequencies in Alzheimer's disease compatible with impaired amyloid clearance}, series = {Neurobiology of Aging}, volume = {120}, journal = {Neurobiology of Aging}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0197-4580}, doi = {10.1016/j.neurobiolaging.2022.08.012}, pages = {117 -- 127}, year = {2022}, abstract = {Retinal vessels are similar to cerebral vessels in their structure and function. Moderately low oscillation frequencies of around 0.1 Hz have been reported as the driving force for paravascular drainage in gray matter in mice and are known as the frequencies of lymphatic vessels in humans. We aimed to elucidate whether retinal vessel oscillations are altered in Alzheimer's disease (AD) at the stage of dementia or mild cognitive impairment (MCI). Seventeen patients with mild-to-moderate dementia due to AD (ADD); 23 patients with MCI due to AD, and 18 cognitively healthy controls (HC) were examined using Dynamic Retinal Vessel Analyzer. Oscillatory temporal changes of retinal vessel diameters were evaluated using mathematical signal analysis. Especially at moderately low frequencies around 0.1 Hz, arterial oscillations in ADD and MCI significantly prevailed over HC oscillations and correlated with disease severity. The pronounced retinal arterial vasomotion at moderately low frequencies in the ADD and MCI groups would be compatible with the view of a compensatory upregulation of paravascular drainage in AD and strengthen the amyloid clearance hypothesis.}, language = {en} } @article{KotliarHauserOrtneretal.2017, author = {Kotliar, Konstantin and Hauser, Christine and Ortner, Marion and Muggenthaler, Claudia and Diehl-Schmid, Janine and Angermann, Susanne and Hapfelmeier, Alexander and Schmaderer, Christoph and Grimmer, Timo}, title = {Altered neurovascular coupling as measured by optical imaging: a biomarker for Alzheimer's disease}, series = {Scientific Reports}, volume = {7}, journal = {Scientific Reports}, number = {1}, publisher = {Springer Nature}, address = {Cham}, issn = {2045-2322}, doi = {10.1038/s41598-017-13349-5}, pages = {1 -- 11}, year = {2017}, language = {en} } @article{StaeudleSeynnesLapsetal.2022, author = {St{\"a}udle, Benjamin and Seynnes, Olivier and Laps, Guido and Br{\"u}ggemann, Gert-Peter and Albracht, Kirsten}, title = {Altered gastrocnemius contractile behavior in former achilles tendon rupture patients during walking}, series = {Frontiers in Physiology}, volume = {13}, journal = {Frontiers in Physiology}, publisher = {Frontiers Research Foundation}, address = {Lausanne}, issn = {1664-042X}, doi = {10.3389/fphys.2022.792576}, pages = {12 Seiten}, year = {2022}, abstract = {Achilles tendon rupture (ATR) remains associated with functional limitations years after injury. Architectural remodeling of the gastrocnemius medialis (GM) muscle is typically observed in the affected leg and may compensate force deficits caused by a longer tendon. Yet patients seem to retain functional limitations during—low-force—walking gait. To explore the potential limits imposed by the remodeled GM muscle-tendon unit (MTU) on walking gait, we examined the contractile behavior of muscle fascicles during the stance phase. In a cross-sectional design, we studied nine former patients (males; age: 45 ± 9 years; height: 180 ± 7 cm; weight: 83 ± 6 kg) with a history of complete unilateral ATR, approximately 4 years post-surgery. Using ultrasonography, GM tendon morphology, muscle architecture at rest, and fascicular behavior were assessed during walking at 1.5 m⋅s-1 on a treadmill. Walking patterns were recorded with a motion capture system. The unaffected leg served as control. Lower limbs kinematics were largely similar between legs during walking. Typical features of ATR-related MTU remodeling were observed during the stance sub-phases corresponding to series elastic element (SEE) lengthening (energy storage) and SEE shortening (energy release), with shorter GM fascicles (36 and 36\%, respectively) and greater pennation angles (8° and 12°, respectively). However, relative to the optimal fascicle length for force production, fascicles operated at comparable length in both legs. Similarly, when expressed relative to optimal fascicle length, fascicle contraction velocity was not different between sides, except at the time-point of peak series elastic element (SEE) length, where it was 39 ± 49\% lower in the affected leg. Concomitantly, fascicles rotation during contraction was greater in the affected leg during the whole stance-phase, and architectural gear ratios (AGR) was larger during SEE lengthening. Under the present testing conditions, former ATR patients had recovered a relatively symmetrical walking gait pattern. Differences in seen AGR seem to accommodate the profound changes in MTU architecture, limiting the required fascicle shortening velocity. Overall, the contractile behavior of the GM fascicles does not restrict length- or velocity-dependent force potentials during this locomotor task.}, language = {en} } @article{BassamArtmannHescheleretal.2011, author = {Bassam, Rasha and Artmann, Gerhard and Hescheler, J{\"u}rgen and Graef, T. and Temiz Artmann, Ayseg{\"u}l and Porst, Dariusz and Linder, Peter and Kayser, Peter and Arinkin, Vladimir and Gossmann, Matthias and Digel, Ilya}, title = {Alterations in human hemoglobin structure related to red blood cell storage}, year = {2011}, abstract = {The importance of the availability of stored blood or blood cells, respectively, for urgent transfusion cannot be overestimated. Nowadays, blood storage becomes even more important since blood products are used for epidemiological studies, bio-technical research or banked for transfusion purposes. Thus blood samples must not only be processed, stored, and shipped to preserve their efficacy and safety, but also all parameters of storage must be recorded and reported for Quality Assurance. Therefore, blood banks and clinical research facilities are seeking more accurate, automated means for blood storage and blood processing.}, subject = {H{\"a}moglobin}, language = {en} }