TY - CHAP A1 - Tran, N. T. A1 - Tran, Thanh Ngoc A1 - Matthies, M. G. A1 - Stavroulakis, G. E. A1 - Staat, Manfred T1 - Shakedown Analysis Under Stochastic Uncertainty by Chance Constrained Programming T2 - Advances in Direct Methods for Materials and Structures N2 - In this paper we propose a stochastic programming method to analyse limit and shakedown of structures under uncertainty condition of strength. Based on the duality theory, the shakedown load multiplier formulated by the kinematic theorem is proved actually to be the dual form of the shakedown load multiplier formulated by static theorem. In this investigation a dual chance constrained programming algorithm is developed to calculate simultaneously both the upper and lower bounds of the plastic collapse limit and the shakedown limit. The edge-based smoothed finite element method (ES-FEM) with three-node linear triangular elements is used for structural analysis. Y1 - 2017 SN - 978-3-319-59810-9 U6 - https://doi.org/10.1007/978-3-319-59810-9_6 SP - 85 EP - 103 PB - Springer CY - Cham ER - TY - GEN A1 - Hackl, Michael A1 - Wegmann, Kilian A1 - Kahmann, Stephanie Lucina A1 - Heinze, Nicolai A1 - Staat, Manfred A1 - Neiss, Wolfram F. A1 - Scaal, Martin A1 - Müller, Lars P. T1 - Reply to the letter to the editor: shortening osteotomy of the proximal radius T2 - Knee Surgery, Sports Traumatology, Arthroscopy Y1 - 2017 U6 - https://doi.org/10.1007/s00167-017-4666-8 VL - 25 IS - 10 SP - 3328 EP - 3329 ER - TY - JOUR A1 - Jayaraman, Chandrasekaran A1 - Mummidisetty, Chaitanya Krishna A1 - Loesch, Alexandra A1 - Kaur, Sandi A1 - Hoppe-Ludwig, Shenan A1 - Staat, Manfred A1 - Jayaraman, Arun T1 - Postural and metabolic benefits of using a forearm support walker in older adults with impairments JF - Archives of Physical Medicine and Rehabilitation Y1 - 2019 U6 - https://doi.org/10.1016/j.apmr.2018.10.001 SN - 0003-9993 VL - Volume 100 IS - Issue 4 SP - 638 EP - 647 PB - Elsevier CY - Amsterdam ER - TY - BOOK A1 - Staat, Manfred A1 - Erni, Daniel T1 - Symposium Proceedings; 3rd YRA MedTech Symposium 2019: May 24 / 2019 / FH Aachen Y1 - 2019 SN - 978-3-940402-22-6 U6 - https://doi.org/10.17185/duepublico/48750 PB - Universität Duisburg-Essen CY - Duisburg ER - TY - CHAP A1 - Hunker, Jan A1 - Jung, Alexander A1 - Goßmann, Matthias A1 - Linder, Peter A1 - Staat, Manfred ED - Staat, Manfred ED - Erni, Daniel T1 - Development of a tool to analyze the conduction speed in microelectrode array measurements of cardiac tissue T2 - 3rd YRA MedTech Symposium 2019 : May 24 / 2019 / FH Aachen N2 - The discovery of human induced pluripotent stem cells reprogrammed from somatic cells [1] and their ability to differentiate into cardiomyocytes (hiPSC-CMs) has provided a robust platform for drug screening [2]. Drug screenings are essential in the development of new components, particularly for evaluating the potential of drugs to induce life-threatening pro-arrhythmias. Between 1988 and 2009, 14 drugs have been removed from the market for this reason [3]. The microelectrode array (MEA) technique is a robust tool for drug screening as it detects the field potentials (FPs) for the entire cell culture. Furthermore, the propagation of the field potential can be examined on an electrode basis. To analyze MEA measurements in detail, we have developed an open-source tool. Y1 - 2019 SN - 978-3-940402-22-6 U6 - https://doi.org/10.17185/duepublico/48750 SP - 7 EP - 8 PB - Universität Duisburg-Essen CY - Duisburg ER - TY - CHAP A1 - Raman, Aravind Hariharan A1 - Jung, Alexander A1 - Horváth, András A1 - Becker, Nadine A1 - Staat, Manfred ED - Staat, Manfred ED - Erni, Daniel T1 - Modification of a computer model of human stem cell-derived cardiomyocyte electrophysiology based on Patch-Clamp measurements T2 - 3rd YRA MedTech Symposium 2019 : May 24 / 2019 / FH Aachen N2 - Human induced pluripotent stem cells (hiPSCs) have shown to be promising in disease studies and drug screenings [1]. Cardiomyocytes derived from hiPSCs have been extensively investigated using patch-clamping and optical methods to compare their electromechanical behaviour relative to fully matured adult cells. Mathematical models can be used for translating findings on hiPSCCMs to adult cells [2] or to better understand the mechanisms of various ion channels when a drug is applied [3,4]. Paci et al. (2013) [3] developed the first model of hiPSC-CMs, which they later refined based on new data [3]. The model is based on iCells® (Fujifilm Cellular Dynamics, Inc. (FCDI), Madison WI, USA) but major differences among several cell lines and even within a single cell line have been found and motivate an approach for creating sample-specific models. We have developed an optimisation algorithm that parameterises the conductances (in S/F=Siemens/Farad) of the latest Paci et al. model (2018) [5] using current-voltage data obtained in individual patch-clamp experiments derived from an automated patch clamp system (Patchliner, Nanion Technologies GmbH, Munich). Y1 - 2019 SN - 978-3-940402-22-6 U6 - https://doi.org/10.17185/duepublico/48750 SP - 10 EP - 11 PB - Universität Duisburg-Essen CY - Duisburg ER - TY - JOUR A1 - Horbach, Andreas A1 - Staat, Manfred A1 - Perez-Viana, Daniel A1 - Simmen, Hans-Peter A1 - Neuhaus, Valentin A1 - Pape, Hans-Christoph A1 - Prescher, Andreas A1 - Ciritsis, Bernhard T1 - Biomechanical in vitro examination of a standardized low-volume tubular femoroplasty JF - Clinical Biomechanics N2 - Background Osteoporosis is associated with the risk of fractures near the hip. Age and comorbidities increase the perioperative risk. Due to the ageing population, fracture of the proximal femur also proves to be a socio-economic problem. Preventive surgical measures have hardly been used so far. Methods 10 pairs of human femora from fresh cadavers were divided into control and low-volume femoroplasty groups and subjected to a Hayes fall-loading fracture test. The results of the respective localization and classification of the fracture site, the Singh index determined by computed tomography (CT) examination and the parameters in terms of fracture force, work to fracture and stiffness were evaluated statistically and with the finite element method. In addition, a finite element parametric study with different position angles and variants of the tubular geometry of the femoroplasty was performed. Findings Compared to the control group, the work to fracture could be increased by 33.2%. The fracture force increased by 19.9%. The used technique and instrumentation proved to be standardized and reproducible with an average poly(methyl methacrylate) volume of 10.5 ml. The parametric study showed the best results for the selected angle and geometry. Interpretation The cadaver studies demonstrated the biomechanical efficacy of the low-volume tubular femoroplasty. The numerical calculations confirmed the optimal choice of positioning as well as the inner and outer diameter of the tube in this setting. The standardized minimally invasive technique with the instruments developed for it could be used in further comparative studies to confirm the measured biomechanical results. Y1 - 2020 U6 - https://doi.org/10.1016/j.clinbiomech.2020.105104 VL - 80 IS - Art. 105104 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Tran, Ngoc Trinh A1 - Staat, Manfred T1 - Direct plastic structural design under random strength and random load by chance constrained programming JF - European Journal of Mechanics - A/Solids Y1 - 2021 U6 - https://doi.org/10.1016/j.euromechsol.2020.104106 SN - 0997-7538 VL - 85 IS - Article 104106 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Bhattarai, Aroj A1 - Horbach, Andreas A1 - Staat, Manfred A1 - Kowalczyk, Wojciech A1 - Tran, Thanh Ngoc T1 - Virgin passive colon biomechanics and a literature review of active contraction constitutive models JF - Biomechanics N2 - The objective of this paper is to present our findings on the biomechanical aspects of the virgin passive anisotropic hyperelasticity of the porcine colon based on equibiaxial tensile experiments. Firstly, the characterization of the intestine tissues is discussed for a nearly incompressible hyperelastic fiber-reinforced Holzapfel–Gasser–Ogden constitutive model in virgin passive loading conditions. The stability of the evaluated material parameters is checked for the polyconvexity of the adopted strain energy function using positive eigenvalue constraints of the Hessian matrix with MATLAB. The constitutive material description of the intestine with two collagen fibers in the submucosal and muscular layer each has been implemented in the FORTRAN platform of the commercial finite element software LS-DYNA, and two equibiaxial tensile simulations are presented to validate the results with the optical strain images obtained from the experiments. Furthermore, this paper also reviews the existing models of the active smooth muscle cells, but these models have not been computationally studied here. The review part shows that the constitutive models originally developed for the active contraction of skeletal muscle based on Hill’s three-element model, Murphy’s four-state cross-bridge chemical kinetic model and Huxley’s sliding-filament hypothesis, which are mainly used for arteries, are appropriate for numerical contraction numerical analysis of the large intestine. KW - virgin passive KW - strain energy function KW - smooth muscle contraction KW - viscoelasticity KW - damage Y1 - 2022 U6 - https://doi.org/10.3390/biomechanics2020013 SN - 2673-7078 VL - 2 IS - 2 SP - 138 EP - 157 PB - MDPI CY - Basel ER - TY - GEN A1 - Jung, Alexander A1 - Müller, Wolfram A1 - Staat, Manfred T1 - Corrigendum to “Wind and fairness in ski jumping: A computer modelling analysis” [J. Biomech. 75 (2018) 147–153] T2 - Journal of Biomechanics Y1 - 2021 U6 - https://doi.org/10.1016/j.jbiomech.2021.110690 SN - 0021-9290 N1 - Refers to: Alexander Jung, Wolfram Müller, Manfred Staat: Wind and fairness in ski jumping: A computer modelling analysis. Journal of Biomechanics, Volume 75. 25 June 2018. Pages 147-153. https://doi.org/10.1016/j.jbiomech.2018.05.001 VL - 128 IS - Article number: 110690 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Jung, Alexander A1 - Staat, Manfred T1 - Erratum to "Modeling and simulation of human induced pluripotent stem cell-derived cardiac tissue" [GAMM-Mitteilungen, (2019), 42, 4, 10.1002/gamm.201900002] JF - GAMM-Mitteilungen Y1 - 2020 U6 - https://doi.org/10.1002/gamm.202000011 SN - 1522-2608 N1 - Refers to: Modeling and simulation of human induced pluripotent stem cell-derived cardiac tissue. Alexander Jung, Manfred Staat. Volume 42, Issue 4. GAMM-Mitteilungen, 2019. https://doi.org/10.1002/gamm.201900002 VL - 43 IS - 4 PB - Wiley-VCH GmbH CY - Weinheim ER - TY - JOUR A1 - Ciritsis, Alexander A1 - Horbach, Andreas A1 - Staat, Manfred A1 - Kuhl, Christiane K. A1 - Kraemer, Nils Andreas T1 - Porosity and tissue integration of elastic mesh implants evaluated in vitro and in vivo JF - Journal of Biomedical Materials Research: Part B: Applied Biomaterials N2 - Purpose In vivo, a loss of mesh porosity triggers scar tissue formation and restricts functionality. The purpose of this study was to evaluate the properties and configuration changes as mesh deformation and mesh shrinkage of a soft mesh implant compared with a conventional stiff mesh implant in vitro and in a porcine model. Material and Methods Tensile tests and digital image correlation were used to determine the textile porosity for both mesh types in vitro. A group of three pigs each were treated with magnetic resonance imaging (MRI) visible conventional stiff polyvinylidene fluoride meshes (PVDF) or with soft thermoplastic polyurethane meshes (TPU) (FEG Textiltechnik mbH, Aachen, Germany), respectively. MRI was performed with a pneumoperitoneum at a pressure of 0 and 15 mmHg, which resulted in bulging of the abdomen. The mesh-induced signal voids were semiautomatically segmented and the mesh areas were determined. With the deformations assessed in both mesh types at both pressure conditions, the porosity change of the meshes after 8 weeks of ingrowth was calculated as an indicator of preserved elastic properties. The explanted specimens were examined histologically for the maturity of the scar (collagen I/III ratio). Results In TPU, the in vitro porosity increased constantly, in PVDF, a loss of porosity was observed under mild stresses. In vivo, the mean mesh areas of TPU were 206.8 cm2 (± 5.7 cm2) at 0 mmHg pneumoperitoneum and 274.6 cm2 (± 5.2 cm2) at 15 mmHg; for PVDF the mean areas were 205.5 cm2 (± 8.8 cm2) and 221.5 cm2 (± 11.8 cm2), respectively. The pneumoperitoneum-induced pressure increase resulted in a calculated porosity increase of 8.4% for TPU and of 1.2% for PVDF. The mean collagen I/III ratio was 8.7 (± 0.5) for TPU and 4.7 (± 0.7) for PVDF. Conclusion The elastic properties of TPU mesh implants result in improved tissue integration compared to conventional PVDF meshes, and they adapt more efficiently to the abdominal wall. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 827–833, 2018. Y1 - 2018 U6 - https://doi.org/10.1002/jbm.b.33877 SN - 1552-4981 VL - 106 IS - 2 SP - 827 EP - 833 PB - Wiley CY - New York, NY ER - TY - JOUR A1 - Hackl, Michael A1 - Wegmann, Kilian A1 - Kahmann, Stephanie Lucina A1 - Heinze, Nicolai A1 - Staat, Manfred A1 - Neiss, Wolfram F. A1 - Scaal, Martin A1 - Müller, Lars P. T1 - Radial shortening osteotomy reduces radiocapitellar contact pressures while preserving valgus stability of the elbow JF - Knee Surgery, Sports Traumatology, Arthroscopy Y1 - 2017 U6 - https://doi.org/10.1007/s00167-017-4468-z SN - 1433-7347 VL - 25 IS - 7 SP - 2280 EP - 2288 PB - Springer CY - Berlin ER - TY - JOUR A1 - Horbach, Andreas A1 - Staat, Manfred T1 - Optical strain measurement for the modeling of surgical meshes and their porosity JF - Current Directions in Biomedical Engineering N2 - The porosity of surgical meshes makes them flexible for large elastic deformation and establishes the healing conditions of good tissue in growth. The biomechanic modeling of orthotropic and compressible materials requires new materials models and simulstaneoaus fit of deformation in the load direction as well as trannsversely to to load. This nonlinear modeling can be achieved by an optical deformation measurement. At the same time the full field deformation measurement allows the dermination of the change of porosity with deformation. Also the socalled effective porosity, which has been defined to asses the tisssue interatcion with the mesh implants, can be determined from the global deformation of the surgical meshes. Y1 - 2018 U6 - https://doi.org/10.1515/cdbme-2018-0045 SN - 2364-5504 VL - Band 4 IS - 1 SP - 181 EP - 184 PB - De Gruyter CY - Berlin ER - TY - JOUR A1 - Bhattarai, Aroj A1 - Staat, Manfred T1 - Computational comparison of different textile implants to correct apical prolapse in females JF - Current Directions in Biomedical Engineering N2 - Prosthetic textile implants of different shapes, sizes and polymers are used to correct the apical prolapse after hysterectomy (removal of the uterus). The selection of the implant before or during minimally invasive surgery depends on the patient’s anatomical defect, intended function after reconstruction and most importantly the surgeon’s preference. Weakness or damage of the supporting tissues during childbirth, menopause or previous pelvic surgeries may put females in higher risk of prolapse. Numerical simulations of reconstructed pelvic floor with weakened tissues and organ supported by textile product models: DynaMesh®-PRS soft, DynaMesh®-PRP soft and DynaMesh®-CESA from FEG Textiletechnik mbH, Germany are compared. Y1 - 2018 U6 - https://doi.org/10.1515/cdbme-2018-0159 VL - 4 IS - 1 SP - 661 EP - 664 PB - De Gruyter CY - Berlin ER - TY - GEN A1 - Topcu, Murat A1 - Madabhushi, Gopal Santana Phani A1 - Staat, Manfred T1 - Datasets from FEM Simulations done with COMSOL Multiphysics and Code_Aster N2 - Datasets from FEM Simulations done with COMSOL Multiphysics and Code_Aster for an elastic stress transfer between matrix and fibres having a variable radius. KW - Natural fibres KW - Polymer-matrix composites KW - Biocomposites KW - Stress concentrations KW - Finite element analysis (FEA) Y1 - 2022 U6 - https://doi.org/10.6084/m9.figshare.19333295.v2 ER - TY - CHAP A1 - Tran, Ngoc Trinh A1 - Trinh, Tu Luc A1 - Dao, Ngoc Tien A1 - Giap, Van Tan A1 - Truong, Manh Khuyen A1 - Dinh, Thuy Ha A1 - Staat, Manfred T1 - Limit and shakedown analysis of structures under random strength T2 - Proceedings of (NACOME2022) The 11th National Conference on Mechanics, Vol. 1. Solid Mechanics, Rock Mechanics, Artificial Intelligence, Teaching and Training N2 - Direct methods comprising limit and shakedown analysis is a branch of computational mechanics. It plays a significant role in mechanical and civil engineering design. The concept of direct method aims to determinate the ultimate load bearing capacity of structures beyond the elastic range. For practical problems, the direct methods lead to nonlinear convex optimization problems with a large number of variables and onstraints. If strength and loading are random quantities, the problem of shakedown analysis is considered as stochastic programming. This paper presents a method so called chance constrained programming, an effective method of stochastic programming, to solve shakedown analysis problem under random condition of strength. In this our investigation, the loading is deterministic, the strength is distributed as normal or lognormal variables. KW - Reliability of structures KW - Stochastic programming KW - Chance constrained programming KW - Shakedown analysis KW - Limit analysis Y1 - 2022 SN - 978-604-357-084-7 N1 - 11th National Conference on Mechanics (NACOME 2022), December 2-3, 2022, VNU University of Engineering and Technology, Hanoi, Vietnam SP - 510 EP - 518 PB - Nha xuat ban Khoa hoc tu nhien va Cong nghe (Verlag Naturwissenschaft und Technik) CY - Hanoi ER - TY - JOUR A1 - Zhen, Manghao A1 - Liang, Yunpei A1 - Staat, Manfred A1 - Li, Quanqui A1 - Li, Jianbo T1 - Discontinuous fracture behaviors and constitutive model of sandstone specimens containing non-parallel prefabricated fissures under uniaxial compression JF - Theoretical and Applied Fracture Mechanics N2 - The deformation and damage laws of non-homogeneous irregular structural planes in rocks are the basis for studying the stability of rock engineering. To investigate the damage characteristics of rock containing non-parallel fissures, uniaxial compression tests and numerical simulations were conducted on sandstone specimens containing three non-parallel fissures inclined at 0°, 45° and 90° in this study. The characteristics of crack initiation and crack evolution of fissures with different inclinations were analyzed. A constitutive model for the discontinuous fractures of fissured sandstone was proposed. The results show that the fracture behaviors of fissured sandstone specimens are discontinuous. The stress–strain curves are non-smooth and can be divided into nonlinear crack closure stage, linear elastic stage, plastic stage and brittle failure stage, of which the plastic stage contains discontinuous stress drops. During the uniaxial compression test, the middle or ends of 0° fissures were the first to crack compared to 45° and 90° fissures. The end with small distance between 0° and 45° fissures cracked first, and the end with large distance cracked later. After the final failure, 0° fissures in all specimens were fractured, while 45° and 90° fissures were not necessarily fractured. Numerical simulation results show that the concentration of compressive stress at the tips of 0°, 45° and 90° fissures, as well as the concentration of tensile stress on both sides, decreased with the increase of the inclination angle. A constitutive model for the discontinuous fractures of fissured sandstone specimens was derived by combining the logistic model and damage mechanic theory. This model can well describe the discontinuous drops of stress and agrees well with the whole processes of the stress–strain curves of the fissured sandstone specimens. KW - Constitutive model KW - Damage mechanics theory KW - Discontinuous fractures KW - Uniaxial compression test KW - Non-parallel fissures Y1 - 2024 U6 - https://doi.org/10.1016/j.tafmec.2024.104373 SN - 0167-8442 VL - 131 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Schieren, Mark A1 - Kleinschmidt, Joris A1 - Schmutz, Axel A1 - Loop, Torsten A1 - Gatzweiler, Karl-Heinz A1 - Staat, Manfred A1 - Wappler, Frank A1 - Defosse, Jerome T1 - Comparison of forces acting on maxillary incisors during tracheal intubation with different laryngoscopy techniques: a blinded manikin study JF - Anaesthesia Y1 - 2019 SN - 1365-2044 U6 - https://doi.org/10.1111/anae.14815 N1 - Die Anhänge "Table S1 (Impact of sex and level of training on dental force. Results presented as median (IQR [range]) and n (%))" und "Appendix S1 (Measurement technique.)" stehen unter "Supporting Information" zum Download bereit. VL - 74 IS - 12 PB - Wiley-Blackwell CY - Oxford ER -