TY - CHAP A1 - Bhattarai, Aroj A1 - Frotscher, Ralf A1 - Sora, M.-C. A1 - Staat, Manfred ED - Onate, E. T1 - A 3D finite element model of the female pelvic floor for the reconstruction of urinary incontinence T2 - 11th World Congress on Computational Mechanics (WCCM XI) ; 5th European Conference on Computational Mechanics (ECCM V) ; 6th European Conference on Computational Fluid Dynamics (ECFD VI) ; July 20-25, 2014, Barcelona Y1 - 2014 SP - 1 EP - 12 ER - TY - CHAP A1 - Staat, Manfred A1 - Heitzer, Michael T1 - The restricted influence of kinematic hardening on shakedown loads N2 - Structural design analyses are conducted with the aim of verifying the exclusion of ratcheting. To this end it is important to make a clear distinction between the shakedown range and the ratcheting range. In cyclic plasticity more sophisticated hardening models have been suggested in order to model the strain evolution observed in ratcheting experiments. The hardening models used in shakedown analysis are comparatively simple. It is shown that shakedown analysis can make quite stable predictions of admissible load ranges despite the simplicity of the underlying hardening models. A linear and a nonlinear kinematic hardening model of two-surface plasticity are compared in material shakedown analysis. Both give identical or similar shakedown ranges. Structural shakedown analyses show that the loading may have a more pronounced effect than the hardening model. KW - Biomedizinische Technik KW - Einspielen KW - Shakedown KW - Ratcheting KW - Bruchmechanik KW - shakedown KW - material shakedown KW - linear kinematic hardening KW - nonlinear kinematic hardening KW - ratchetting Y1 - 2002 ER - TY - CHAP A1 - Dachwald, Bernd A1 - Kahle, Ralph A1 - Wie, Bong T1 - Solar sail Kinetic Energy Impactor (KEI) mission design tradeoffs for impacting and deflecting asteroid 99942 Apophis T2 - AIAA/AAS Astrodynamics Specialist Conference and Exhibit N2 - Near-Earth asteroid 99942 Apophis provides a typical example for the evolution of asteroid orbits that lead to Earth-impacts after a close Earth-encounter that results in a resonant return. Apophis will have a close Earth-encounter in 2029 with potential very close subsequent Earth-encounters (or even an impact) in 2036 or later, depending on whether it passes through one of several so-called gravitational keyholes during its 2029-encounter. Several pre-2029-deflection scenarios to prevent Apophis from doing this have been investigated so far. Because the keyholes are less than 1 km in size, a pre-2029 kinetic impact is clearly the best option because it requires only a small change in Apophis' orbit to nudge it out of a keyhole. A single solar sail Kinetic Energy Impactor (KEI) spacecraft that impacts Apophis from a retrograde trajectory with a very high relative velocity (75-80 km/s) during one of its perihelion passages at about 0.75 AU would be a feasible option to do this. The spacecraft consists of a 160 m x 160 m, 168 kg solar sail assembly and a 150 kg impactor. Although conventional spacecraft can also achieve the required minimum deflection of 1 km for this approx. 320 m-sized object from a prograde trajectory, our solar sail KEI concept also allows the deflection of larger objects. In this paper, we also show that, even after Apophis has flown through one of the gravitational keyholes in 2029, solar sail Kinetic Energy Impactor (KEI) spacecraft are still a feasible option to prevent Apophis from impacting the Earth, but many KEIs would be required for consecutive impacts to increase the total Earth-miss distance to a safe value. In this paper, we elaborate potential pre- and post-2029 KEI impact scenarios for a launch in 2020, and investigate tradeoffs between different mission parameters. KW - Solar Sail KW - Asteroid Deflection KW - Planetary Protection KW - Trajectory Optimization Y1 - 2006 U6 - https://doi.org/10.2514/6.2006-6178 N1 - AIAA/AAS Astrodynamics Specialist Conference and Exhibit, 21 August 2006 - 24 August 2006, Keystone, Colorado(USA). SP - 1 EP - 20 ER - TY - CHAP A1 - Staat, Manfred T1 - Problems and chances for probabilistic fracture mechanics in the analysis of steel pressure boundary reliability. - Überarb. Ausg. N2 - In: Technical feasibility and reliability of passive safety systems for nuclear power plants. Proceedings of an Advisory Group Meeting held in Jülich, 21-24 November 1994. - Vienna , 1996. - Seite: 43 - 55 IAEA-TECDOC-920 Abstract: It is shown that the difficulty for probabilistic fracture mechanics (PFM) is the general problem of the high reliability of a small population. There is no way around the problem as yet. Therefore what PFM can contribute to the reliability of steel pressure boundaries is demon­strated with the example of a typical reactor pressure vessel and critically discussed. Although no method is distinguishable that could give exact failure probabilities, PFM has several addi­tional chances. Upper limits for failure probability may be obtained together with trends for design and operating conditions. Further, PFM can identify the most sensitive parameters, improved control of which would increase reliability. Thus PFM should play a vital role in the analysis of steel pressure boundaries despite all shortcomings. KW - Bruchmechanik KW - probabilistic fracture mechanics KW - PFM Y1 - 2006 ER - TY - CHAP A1 - Tran, Thanh Ngoc A1 - Staat, Manfred A1 - Kreißig, R. T1 - Calculation of load carrying capacity of shell structures with elasto-plastic material by direct methods N2 - Proceedings of the International Conference on Material Theory and Nonlinear Dynamics. MatDyn. Hanoi, Vietnam, Sept. 24-26, 2007, 8 p. In this paper, a method is introduced to determine the limit load of general shells using the finite element method. The method is based on an upper bound limit and shakedown analysis with elastic-perfectly plastic material model. A non-linear constrained optimisation problem is solved by using Newton’s method in conjunction with a penalty method and the Lagrangean dual method. Numerical investigation of a pipe bend subjected to bending moments proves the effectiveness of the algorithm. KW - Finite-Elemente-Methode Y1 - 2007 ER - TY - CHAP A1 - Tran, Thanh Ngoc A1 - Novacek, V. A1 - Tolba, R. A1 - Klinge, U. A1 - Turquier, F. A1 - Staat, Manfred T1 - Experimental and Computational approach to study colorectal anastomosis. ISB2011, Proceedings of the XXIII Congress of the International Society of Biomechanics, Brussels, Belgium, July 3-7, 2011 N2 - Summary: This paper presents a methodology to study and understand the mechanics of stapled anastomotic behaviors by combining empirical experimentation and finite element analysis. Performance of stapled anastomosis is studied in terms of leakage and numerical results which are compared to in vitro experiments performed on fresh porcine tissue. Results suggest that leaks occur between the tissue and staple legs penetrating through the tissue. KW - Anastomose KW - Finite-Elemente-Methode KW - Biomechanik KW - Anastomosis KW - Finite element method KW - Biomechanics Y1 - 2011 ER - TY - CHAP A1 - Baader, Fabian A1 - Keller, Denis A1 - Lehmann, Raphael A1 - Gerber, Lukas A1 - Reiswich, Martin A1 - Dachwald, Bernd A1 - Förstner, Roger T1 - Operating melting probes for ice penetration under sublimation conditions and in reduced gravity on a sounding rocket T2 - Proceedings of the 24th ESA Symposium on European Rocket and Balloon Programmes and related Research Y1 - 2019 SN - 0379-6566 N1 - 24th PAC Symposium 2019 ER - TY - CHAP A1 - Borggräfe, Andreas A1 - Dachwald, Bernd T1 - Mission performance evaluation for solar sails using a refined SRP force model with variable optical coefficients T2 - 2nd International Symposium on Solar Sailing N2 - Solar sails provide ignificant advantages over other low-thrust propulsion systems because they produce thrust by the momentum exchange from solar radiation pressure (SRP) and thus do not consume any propellant.The force exerted on a very thin sail foil basically depends on the light incidence angle. Several analytical SRP force models that describe the SRP force acting on the sail have been established since the 1970s. All the widely used models use constant optical force coefficients of the reflecting sail material. In 2006,MENGALI et al. proposed a refined SRP force model that takes into account the dependancy of the force coefficients on the light incident angle,the sail’s distance from the sun (and thus the sail emperature) and the surface roughness of the sail material [1]. In this paper, the refined SRP force model is compared to the previous ones in order to identify the potential impact of the new model on the predicted capabilities of solar sails in performing low-cost interplanetary space missions. All force models have been implemented within InTrance, a global low-thrust trajectory optimization software utilizing evolutionary neurocontrol [2]. Two interplanetary rendezvous missions, to Mercury and the near-Earth asteroid 1996FG3, are investigated. Two solar sail performances in terms of characteristic acceleration are examined for both scenarios, 0.2 mm/s2 and 0.5 mm/s2, termed “low” and “medium” sail performance. In case of the refined SRP model, three different values of surface roughness are chosen, h = 0 nm, 10 nm and 25 nm. The results show that the refined SRP force model yields shorter transfer times than the standard model. Y1 - 2010 N1 - 2nd International Symposium on Solar Sailing, ISSS 2010, 2010-07-20 - 2010-07-22. New York City College of Technology of the City University of New York, USA SP - 1 EP - 6 ER - TY - CHAP A1 - Tran, Ngoc Trinh A1 - Staat, Manfred T1 - FEM shakedown analysis of Kirchhoff-Love plates under uncertainty of strength T2 - Proceedings of UNCECOMP 2021 N2 - A new formulation to calculate the shakedown limit load of Kirchhoff plates under stochastic conditions of strength is developed. Direct structural reliability design by chance con-strained programming is based on the prescribed failure probabilities, which is an effective approach of stochastic programming if it can be formulated as an equivalent deterministic optimization problem. We restrict uncertainty to strength, the loading is still deterministic. A new formulation is derived in case of random strength with lognormal distribution. Upper bound and lower bound shakedown load factors are calculated simultaneously by a dual algorithm. Y1 - 2021 SN - 978-618-85072-6-5 U6 - https://doi.org/10.7712/120221.8041.19047 N1 - UNCECOMP 2021, 4th International Conference on Uncertainty Quantification in Computational Sciences and Engineering, streamed from Athens, Greece, 28–30 June 2021. SP - 323 EP - 338 ER - TY - CHAP A1 - Schoutetens, Frederic A1 - Dachwald, Bernd A1 - Heiligers, Jeannette T1 - Optimisation of photon-sail trajectories in the alpha-centauri system using evolutionary neurocontrol T2 - 8th ICATT 2021 N2 - With the increased interest for interstellar exploration after the discovery of exoplanets and the proposal by Breakthrough Starshot, this paper investigates the optimisation of photon-sail trajectories in Alpha Centauri. The prime objective is to find the optimal steering strategy for a photonic sail to get captured around one of the stars after a minimum-time transfer from Earth. By extending the idea of the Breakthrough Starshot project with a deceleration phase upon arrival, the mission’s scientific yield will be increased. As a secondary objective, transfer trajectories between the stars and orbit-raising manoeuvres to explore the habitable zones of the stars are investigated. All trajectories are optimised for minimum time of flight using the trajectory optimisation software InTrance. Depending on the sail technology, interstellar travel times of 77.6-18,790 years can be achieved, which presents an average improvement of 30% with respect to previous work. Still, significant technological development is required to reach and be captured in the Alpha-Centauri system in less than a century. Therefore, a fly-through mission arguably remains the only option for a first exploratory mission to Alpha Centauri, but the enticing results obtained in this work provide perspective for future long-residence missions to our closest neighbouring star system. Y1 - 2021 N1 - 8th ICATT (International Conference on Astrodynamics Tools and Techniques), 23 - 25 June 2021, Virtual SP - 1 EP - 15 ER - TY - CHAP A1 - Seefeldt, Patric A1 - Bauer, Waldemar A1 - Dachwald, Bernd A1 - Grundmann, Jan Thimo A1 - Straubel, Marco A1 - Sznajder, Maciej A1 - Tóth, Norbert A1 - Zander, Martin E. T1 - Large lightweight deployable structures for planetary defence: solar sail propulsion, solar concentrator payloads, large-scale photovoltaic power T2 - 4th IAA Planetary Defense Conference - PDC 2015, 13-17 April 2015, Frascati, Roma, Italy Y1 - 2015 N1 - IAA-PDC-15-P-20 ER - TY - CHAP A1 - Digel, Ilya A1 - Demirci, Taylan A1 - Trzewik, Jürgen A1 - Linder, Peter A1 - Temiz Artmann, Aysegül T1 - Fibroblast response to mechanical stress: role of the adhesion substrate : [abstract] N2 - Mechanical stimulation of the cells resulted in evident changes in the cell morphology, protein composition and gene expression. Microscopically, additional formation of stress fibers accompanied by cell re-arrangements in a monolayer was observed. Also, significant activation of p53 gene was revealed as compared to control. Interestingly, the use of CellTech membrane coating induced cell death after mechanical stress had been applied. Such an effect was not detected when fibronectin had been used as an adhesion substrate. KW - Fibroblast KW - Mechanische Beanspruchung KW - celldrum technology Y1 - 2004 ER - TY - CHAP A1 - Loeb, Horst W. A1 - Schartner, Karl-Heinz A1 - Dachwald, Bernd A1 - Ohndorf, Andreas A1 - Seboldt, Wolfgang T1 - An Interstellar – Heliopause mission using a combination of solar/radioisotope electric propulsion T2 - Presented at the 32nd International Electric Propulsion Conference N2 - 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. Y1 - 2011 N1 - 32nd International Electric Propulsion Conference, 11-15 September. Wiesbaden, Germany SP - 1 EP - 7 ER - TY - CHAP A1 - Pohle-Fröhlich, Regina A1 - Dalitz, Christoph A1 - Richter, Charlotte A1 - Hahnen, Tobias A1 - Stäudle, Benjamin A1 - Albracht, Kirsten T1 - Estimation of muscle fascicle orientation in ultrasonic images T2 - Proceedings of the 15th International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications - Volume 5 N2 - We compare four different algorithms for automatically estimating the muscle fascicle angle from ultrasonic images: the vesselness filter, the Radon transform, the projection profile method and the gray level cooccurence matrix (GLCM). The algorithm results are compared to ground truth data generated by three different experts on 425 image frames from two videos recorded during different types of motion. The best agreement with the ground truth data was achieved by a combination of pre-processing with a vesselness filter and measuring the angle with the projection profile method. The robustness of the estimation is increased by applying the algorithms to subregions with high gradients and performing a LOESS fit through these estimates. Y1 - 2020 SN - 978-989-758-402-2 U6 - https://doi.org/10.5220/0008933900790086 N1 - 15th International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications VISAPP 2020, Valletta, Malta SP - 79 EP - 86 PB - SciTePress CY - Setúbal, Portugal ER - TY - CHAP A1 - Mandekar, Swati A1 - Jentsch, Lina A1 - Lutz, Kai A1 - Behbahani, Mehdi A1 - Melnykowycz, Mark T1 - Earable design analysis for sleep EEG measurements T2 - UbiComp '21 N2 - Conventional EEG devices cannot be used in everyday life and hence, past decade research has been focused on Ear-EEG for mobile, at-home monitoring for various applications ranging from emotion detection to sleep monitoring. As the area available for electrode contact in the ear is limited, the electrode size and location play a vital role for an Ear-EEG system. In this investigation, we present a quantitative study of ear-electrodes with two electrode sizes at different locations in a wet and dry configuration. Electrode impedance scales inversely with size and ranges from 450 kΩ to 1.29 MΩ for dry and from 22 kΩ to 42 kΩ for wet contact at 10 Hz. For any size, the location in the ear canal with the lowest impedance is ELE (Left Ear Superior), presumably due to increased contact pressure caused by the outer-ear anatomy. The results can be used to optimize signal pickup and SNR for specific applications. We demonstrate this by recording sleep spindles during sleep onset with high quality (5.27 μVrms). KW - EEG KW - sensors KW - Impedance Spectroscopy KW - Sleep EEG KW - biopotential electrodes Y1 - 2021 U6 - https://doi.org/10.1145/3460418.3479328 N1 - UbiComp '21: Adjunct Proceedings of the 2021 ACM International Joint Conference on Pervasive and Ubiquitous Computing and Proceedings of the 2021 ACM International Symposium on Wearable Computers, September 21–26, 2021, Virtual, USA SP - 171 EP - 175 ER - TY - CHAP A1 - Goldmann, Jan-Peter A1 - Braunstein, Bjoern A1 - Heinrich, Kai A1 - Sanno, Maximilian A1 - Stäudle, Benjamin A1 - Ritzdorf, Wolfgang A1 - Brüggemann, Gert-Peter A1 - Albracht, Kirsten T1 - Joint work of the take-off leg during elite high jump T2 - Proceedings of the 33th International Conference on Biomechanics in Sports (ISBS) Y1 - 2015 ER - TY - CHAP A1 - Droszez, Anna A1 - Sanno, Maximilian A1 - Goldmann, Jan-Peter A1 - Albracht, Kirsten A1 - Brüggemann, Gerd-Peter A1 - Braunstein, Bjoern T1 - Differences between take-off behavior during vertical jumps and two artistic elements T2 - 34th International Conference of Biomechanics in Sport, Tsukuba, Japan, July 18-22, 2016 Y1 - 2016 SN - 1999-4168 SP - 577 EP - 580 ER - TY - CHAP A1 - Abel, Thomas A1 - Bonin, Dominik A1 - Albracht, Kirsten A1 - Zeller, Sebastian A1 - Brüggemann, Gert-Peter A1 - Burkett, Brendan A1 - Strüder, Heiko K. T1 - Kinematic profile of the elite handcyclist T2 - 28th International Conference on Biomechanics in Sports, Marquette, Michigan, USA, July 19 – 23, 2010 Y1 - 2017 SN - 1999-4168 SP - 140 EP - 141 ER - TY - CHAP A1 - Braunstein, Bjoern A1 - Goldmann, Jan-Peter A1 - Albracht, Kirsten A1 - Sanno, Maximilian A1 - Willwacher, Steffen A1 - Heinrich, Kai A1 - Herrmann, Volker A1 - Brüggemann, Gert-Peter T1 - Joint specific contribution of mechanical power and work during acceleration and top speed in elite sprinters T2 - 31 International Conference on Biomechanics in Sports, Taipei, Taiwan, July 07 - July 22, 2013 Y1 - 2013 SN - 1999-4168 ER - TY - CHAP A1 - Kolditz, Melanie A1 - Albracht, Kirsten A1 - Fasse, Alessandro A1 - Albin, Thivaharan A1 - Brüggemann, Gert-Peter A1 - Abel, Dirk T1 - Evaluation of an industrial robot as a leg press training device T2 - XV International Symposium on Computer Simulation in Biomechanics July 9th – 11th 2015, Edinburgh, UK Y1 - 2015 SP - 41 EP - 42 ER -