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  • 151.
    Tibert, Gunnar
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Distributed indeterminacy in frameworks2005In: Proceedings of the 5th International Conference on Computation of Shell and Spatial Structures, 2005Conference paper (Refereed)
  • 152.
    Tibert, Gunnar
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Flexibility evaluation of prestressed kinematically indeterminate frameworks2005In: NSCM-18: Proceedings of the 18th Nordic Seminar on Computational Mechanics, 2005Conference paper (Refereed)
  • 153.
    Tibert, Gunnar
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Optimal design of tension truss antennas2003In: Proceedings of the 44th AIAA/ASME/ASCE/AHS Structures, Structural Dynamics, and Materials Conference, American Institute of Aeronautics and Astronautics, 2003, p. AIAA-2003-1629-Conference paper (Refereed)
  • 154.
    Tibert, Gunnar
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Hedlund, Erik
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Surface accuracy analysis of torus-supported inflatable reflector antennas2007In: Proceedings of Structural Membranes 2007, Barcelona, Spain: CIMNE , 2007, p. 133-136Conference paper (Refereed)
  • 155.
    Tibert, Gunnar
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Krantz, Magnus
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Teaching principal stresses by truss analogies2006In: Proceedings of the 19th Nordic Seminar on Computational Mechanics, 2006, p. 147-150Conference paper (Refereed)
  • 156.
    Tibert, Gunnar
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Lennon, Andrew
    Lessons from structural design of a highly-flexible space structure: the space-tow solar sail2007In: Proceedings of the First CEAS European Air and Space Conference, 2007, p. CEAS-2007-251-Conference paper (Refereed)
  • 157.
    Tibert, Gunnar
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Pellegrino, Sergio
    University of Cambridge.
    Deployable tensegrity masts2003In: Proceedings of the 44th AIAA/ASME/ASCE/AHS Structures, Structural Dynamics, and Materials Conference, American Institute of Aeronautics and Astronautics, 2003, p. AIAA-2003-1978-Conference paper (Refereed)
  • 158.
    Tibert, Gunnar
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Pellegrino, Sergio
    University of Cambridge.
    Form-finding of tensegrity structures - a review2001In: NSCM-14: Proceedings of the 14th Nordic Seminar on Computational Mechanics, 2001, p. 133-136Conference paper (Refereed)
  • 159.
    Tibert, Gunnar
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Pellegrino, Sergio
    University of Cambridge.
    Furlable reflector concept for small satellites2001In: Proceedings of the 42nd AIAA/ASME/ASCE/AHS Structures, Structural Mechanics, and Materials Conference, American Institute of Aeronautics and Astronautics, 2001, p. AIAA-2001-1261-Conference paper (Refereed)
  • 160.
    Tibert, Gunnar
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Pellegrino, Sergio
    Review of form-finding methods for tensegrity structures2011In: International Journal of Space Structures, ISSN 0266-3511, Vol. 26, no 3, p. 241-255Article in journal (Refereed)
    Abstract [en]

    Seven form-finding methods for tensegrity structures are reviewed and classified. The three kinematical methods include an analytical approach, a non-linear optimisation, and a pseudo-dynamic iteration. The four statical methods include an analytical method, the formulation of linear equations of equilibrium in terms of force densities, an energy minimisation, and a search for the equilibrium configurations of the struts of the structure connected by cables whose lengths are to be determined, using a reduced set of equilibrium equations. It is concluded that the kinematical methods are best suited to obtaining only configuration details of structures that are already essentially known. The force density method is best suited to searching for new configurations, but affords no control over the lengths of the elements of the structure. The reduced coordinates method offers a greater control on elements lengths, but requires more extensive symbolic manipulations.

  • 161.
    Tibert, Gunnar
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Pellegrino, Sergio
    University of Cambridge.
    Review of form-finding methods for tensegrity structures2003In: International Journal of Space Structures, ISSN 0266-3511, Vol. 18, no 4, p. 209-223Article in journal (Refereed)
  • 162.
    Vasile, Massimiliano
    et al.
    Univ. of Strathclyde.
    Cartmell, Matthew
    Univ. of Glasgow.
    Zerihun Dejene, Firew
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Drysdale, T.
    Alaniz Flores, Monica
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Gulzar, Muhammad
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Ismail, N.
    Khalid, Muhammad Usman
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Li, M.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Maddock, C.
    Mallol, Pau
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Mathieson, A.
    McRobb, M.
    Öberg, Johnny
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Purcell, O.
    Reynolds, P.
    Ritterbusch, Rafael
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Sandqvist, William
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Summerer, L.
    Tanveer, Muhammad Usman
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Tibert, Gunnar
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Whyte, G.
    Zafar, W.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Zhang, J.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    The Suaineadh Project: a Stepping Stone Towards the Deployment of Large Flexible Structures in Space2010In: Proceedings of the 61st International Astronautical Congress, the International Astronautical Federation , 2010, p. IAC-10-C3.4-Conference paper (Refereed)
    Abstract [en]

    The Suaineadh project aims at testing the controlled deployment and stabilization of space web. The deployment system is based on a simple yet ingenious control of the centrifugal force that will pull each of the four daughters sections apart. The four daughters are attached onto the four corners of a square web, and will be released from their initial stowed configuration attached to a central hub. Enclosed in the central hub is a specifically designed spinning reaction wheel that controls the rotational speed with a closed loop control fed by measurements from an onboard inertial measurement sensor. Five other such sensors located within the web and central hub provide information on the surface curvature of the web, and progression of the deployment. Suaineadh is currently at an advanced stage of development: all the components are manufactured with the subsystems integrated and are presently awaiting full integration and testing. This paper will present the current status of the Suaineadh project and the results of the most recent set of tests. In particular, the paper will cover the overall mechanical design of the system, the electrical and sensor assemblies, the communication and power systems and the spinning wheel with its control system.

  • 163.
    Wang, Ruoli
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Biomechanical consequences of gait impairment at the ankle and foot: Injury, malalignment, and co-contraction2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The human foot contributes significantly to the function of the whole lower extremity during standing and locomotion. Nevertheless, the foot and ankle often suffer injuries and are affected by many musculoskeletal and neurological pathologies. The overall aim of this thesis was to evaluate gait parameters and muscle function change due to foot and ankle injury, malalignment and co-contraction. Using 3D gait analysis, analytical analyses and computational simulations, biomechanical consequences of gait impairment at the ankle and foot were explored in ablebodied persons and in patient groups with disorders affecting walking.

    We have characterized gait patterns of subjects with ankle fractures with a modified multi-segment foot model. The inter-segmental foot kinematics were determined during gait in 18 subjects one year after surgically-treated ankle fractures. Gait data were compared to an age- and gender-matched control group and the correlations between functional ankle score and gait parameters were determined. It was observed that even with fairly good clinical results, restricted range of motion and malalignment at and around the injured area were found in the injured limb.

    Moment-angle relationship (dynamic joint stiffness) - the relationship between changes in joint moment and changes in joint angle - is useful for demonstrating interaction of kinematics and kinetics during gait. Ankle dynamic joint stiffness during the stance phase of gait was analyzed and decomposed into three components in thirty able-bodied children, eight children with juvenile idiopathic arthritis and eight children with idiopathic toe-walking. Compared to controls, the component associated with changes of ground reaction moment was the source of highest deviation in both pathological groups. Specifically, ankle dynamic joint stiffness differences can be further identified via two subcomponents of this component which are based on magnitudes and rates of change of the ground reaction force and of its moment arm. And differences between the two patient groups and controls were most evident and interpretable here.

    Computational simulations using 3D musculoskeltal models can be powerful in investigating movement mechanisms, which are not otherwise possible or ethical to measure experimentally. We have quantified the effect of subtalar malalignment on the potential dynamic function of the main ankle dorsiflexors and plantarflexors: the gastrocnemius, soleus and tibialis anterior. Induced acceleration analysis was used to compute muscle-induced joint angular and body center of mass accelerations. A three-dimensional subject-specific linkage model was configured by gait data and driven by 1 Newton of individual muscle force. The excessive subtalar inversion or eversion was modified by offsetting up to ±20˚ from the normal subtalar angle while other configurations remain unaltered. We confirmed that in normal gait, muscles generally acted as their anatomical definitions, and that muscles can create motion in many joints, even those not spanned by the muscles. Excessive subtalar eversion was found to enlarge the plantarflexors’ and tibialis anterior’s function.

    In order to ascertain the reliability of muscle function computed from simulations, we have also performed a parametric study on eight healthy adults to evaluate how sensitive the muscle-induced joints’ accelerations are to the parameters of rigid foot-ground contact model. We quantified accelerations induced by the gastrocnemius, soleus and tibialis anterior on the lower limb joints. Two types of models, a ‘fixed joint’ model with three fixed joints under the foot and a ‘moving joint’ model with one joint located along the moving center of pressure were evaluated. The influences of different foot-ground contact joint constraints and locations of center of pressure were also investigated. Our findings indicate that both joint locations and prescribed degrees-of-freedom of models affect the predicted potential muscle function, wherein the joint locations are most influential. The pronounced influences can be observed in the non-sagittal plane.

    Excessive muscle co-contraction is a cause of inefficient or abnormal movement in some neuromuscular pathologies. We have identified the necessary compensation strategies to overcome excessive antagonistic muscle cocontraction at the ankle joint and retain a normal walking pattern. Muscle-actuated simulation of normal walking and induced acceleration analysis were performed to quantify compensatory mechanisms of the primary ankle and knee muscles in the presence of normal, medium and high levels of co-contraction of two antagonistic pairs (gastrocnemiustibialis anterior and soleus-tibialis anterior). The study showed that if the co-contraction level increases, the nearby synergistic muscles can contribute most to compensation in the gastrocnemius-tibialis anterior pair. In contrast, with the soleus-tibialis anterior co-contraction, the sartorius and hamstrings can provide important compensatory roles in knee accelerations.

    This dissertation documented a broad range of gait mechanisms and muscle functions in the foot and ankle area employing both experiments and computational simulations. The strategies and mechanisms in which altered gait and muscles activation are used to compensate for impairment can be regarded as references for evaluation of future patients and for dynamic muscle functions during gait.

  • 164.
    Wang, Ruoli
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Broström, Eva
    Women's and Children's Health, Karolinska Institutet.
    Esbjörnsson, Anna-Clara
    Women's and Children's Health, Karolinska Institutet.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Analytical decomposition can help to interpret ankle joint moment-angle relationship2012In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 22, no 4, p. 566-574Article in journal (Refereed)
    Abstract [en]

    Moment-angle relationship (dynamic joint stiffness) - the relationship between changes in joint moment and changes in joint angle - is useful for demonstrating interaction of kinematics and kinetics during gait. However, the individual contributors of dynamic joint stiffness are not well studied and understood, which has thus far limited its clinical application. In this study, ankle dynamic joint stiffness was analyzed and decomposed into three components in thirty able-bodied children during the stance phase of the gait. To verify the accuracy of the decomposition, the sum of decomposed components was compared to stiffness computed from experimental data, and good to very good agreement was found. Component 1, the term associated with changes in ground reaction force moment, was the dominant contribution to ankle dynamic joint stiffness. Retrospective data from eight children with juvenile idiopathic arthritis and idiopathic toe-walking was examined to explore the potential utility of analytical decomposition in pathological gait. Compared to controls, component 1 was the source of highest deviation in both pathological groups. Specifically, ankle dynamic joint stiffness differences can be further identified via two sub-components of component 1 which are based on magnitudes and rates of change of the ground reaction force and of its moment arm, and differences between the two patient groups and controls were most evident and interpretable here. Findings of the current study indicate that analytical decomposition can help identify the individual contributors to joint stiffness and clarify the sources of differences in patient groups.

  • 165.
    Wang, Ruoli
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Gutierrez Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    The effect of subtalar inversion/eversion on the dynamic function of the tibialis anterior, soleus, and gastrocnemius during the stance phase of gait2011In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 34, no 1, p. 29-35Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to determine how gait deviation in one plane (i.e. excessive subtalar inversion/eversion) can affect the dynamic function of the tibialis anterior, gastrocnemius, and soleus to accelerate the subtalar, ankle, knee and hip joints, as well as the body center of mass. Induced acceleration analysis was performed based on a subject-specific three-dimensional linkage model configured by stance phase gait data and driven by one unit of muscle force. Eight healthy adult subjects were examined in gait analysis. The subtalar inversion/eversion was modeled by offsetting up to 20 from the normal subtalar angle while other configurations remained unaltered. This study showed that the gastrocnemius, soleus and tibialis anterior generally functioned as their anatomical definition in normal gait, but counterintuitive function was occasionally found in the bi-articular gastrocnemius. The plantarflexors play important roles in the body support and forward progression. Excessive subtalar eversion was found to enlarge the plantarflexors and tibialis anterior's function. Induced acceleration analysis demonstrated its ability to isolate the contributions of individual muscle to a given factor, and as a means of studying effect of pathological gait on the dynamic muscle functions.

  • 166.
    Wang, Ruoli
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    A parametric study of the rigid foot-ground contact model: effects on induced angular accelerations of the lower limb joints in the stance-phaseManuscript (preprint) (Other academic)
  • 167.
    Wang, Ruoli
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Compensatory strategies in response to excessive muscle co-contraction at the ankle joint during walkingManuscript (preprint) (Other academic)
  • 168.
    Xiao, Heng
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Co-rotational thin membrane elements2005In: Proc 5th Int. Conf. Computation of Shell and Spatial Structures / [ed] E. Ramm, W.A. Wall, K.-U.Bletzinger, M. Bischoff, 2005Conference paper (Refereed)
    Abstract [en]

    The co-rotational (CR) technique is a kinematics description, which can be tracedback to work by Wempner1. Up to now, most of the research efforts on a co-rotationalframework have been focused on beams and shells, but there are also some investigationsextending the CR procedures to other continuum elements. A recent review of the stateof the art of CR formulation is given by Felippa and Hauge2.The concept of an element-independent co-rotational (EICR) formulation has beenproposed by Rankin and coworkers3, with its most significant feature that extraction andintegration of rigid body motion can be done in a module called CR filter, independentof linear element calculation.A unified approach to the finite element method in a co-rotational (CR) frameworkis proposed. A commonly applicable filter was developed according to the framework,with which many nonlinear CR elements can be easily developed by integrating the filterwith corresponding linear elements. The main points of the developed procedure is agenerality in basic formulation, and an algorithm based on nodal contributions. The CRfilter is formulated as a strict minimization problem, which is solved by rapidly convergingNewton iterations.Three continuum elements were developed in this framework4. Numerical exampleswith large displacements were tested with the CR elements developed in this way. Thetest results and the performance of the elements are analyzed, and conclusions are drawn,proving the unified approach to be promising, but also indicating the main problems withthe CR framework.

  • 169.
    Yadav, Priti
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics. KTH, School of Engineering Sciences (SCI), Centres, BioMEx.
    Multiscale Modelling of Proximal Femur Growth: Importance of Geometry and Influence of Load2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Longitudinal growth of long bone occurs at growth plates by a process called endochondral ossification. Endochondral ossification is affected by both biological and mechanical factors. This thesis focuses on the mechanical modulation of femoral bone growth occurring at the proximal growth plate, using mechanobiological theories reported in the literature. Finite element analysis was used to simulate bone growth.

    The first study analyzed the effect of subject-specific growth plate geometry over simplified growth plate geometry in numerical prediction of bone growth tendency. Subject-specific femur finite element model was constructed from magnetic resonance images of one able- bodied child. Gait kinematics and kinetics were acquired from motion analysis and analyzed further in musculoskeletal modelling to determine muscle and joint contact forces. These were used to determine loading on the femur in finite element analysis. The growth rate was computed based on a mechanobiological theory proposed by Carter and Wong, and a growth model in the principal stress direction was introduced. Our findings support the use of subject- specific geometry and of the principal stress growth direction in prediction of bone growth.

    The second study aimed to illustrate how different muscle groups’ activation during gait affects proximal femoral growth tendency in able-bodied children. Subject-specific femur models were used. Gait kinematics and kinetics were acquired for 3 able-bodied children, and muscle and joint contact forces were determined, similar to the first study. The contribution of different muscle groups to hip contact force was also determined. Finite element analysis was performed to compute the specific growth rate and growth direction due to individual muscle groups. The simulated growth model indicated that gait loading tends to reduce neck shaft angle and femoral anteversion during growth. The muscle groups that contributes most and least to growth rate were hip abductors and hip adductors, respectively. All muscle groups’ activation tended to reduce the neck shaft and femoral anteversion angles, except hip extensors and adductors which showed a tendency to increase the femoral anteversion.

    The third study’s aim was to understand the influence of different physical activities on proximal femoral growth tendency. Hip contact force orientation was varied to represent reported forces from a number of physical activities. The findings of this study showed that all studied physical activities tend to reduce the neck shaft angle and anteversion, which corresponds to the femur’s natural course during normal growth.

    The aim of the fourth study was to study the hypothesis that loading in the absence of physical activity, i.e. static loading, can have an adverse effect on bone growth. A subject-specific model was used and growth plate was modeled as a poroelastic material in finite element analysis. Prendergast’s indicators for bone growth was used to analyse the bone growth behavior. The results showed that tendency of bone growth rate decreases over a long duration of static loading. The study also showed that static sitting is less detrimental than static standing for predicted cartilage-to-bone differentiation likelihood, due to the lower magnitude of hip contact force.

    The prediction of growth using finite element analysis on experimental gait data and person- specific femur geometry, based on mechanobiological theories of bone growth, offers a biomechanical foundation for better understanding and prediction of bone growth-related deformity problems in growing children. It can ultimately help in treatment planning or physical activity guidelines in children at risk at developing a femur or hip deformity. 

  • 170.
    Yadav, Priti
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    How can the load directions due to different physical activities affect proximal femoral growth tendency?Manuscript (preprint) (Other academic)
  • 171.
    Yadav, Priti
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Modelling the effects of static load on proximal femoral growth behaviorManuscript (preprint) (Other academic)
  • 172. Yamada, Takashi
    et al.
    Bruton, Joseph D.
    Place, Nicolas
    Zhang, Shi-jin
    Kosterina, Natalia
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Harris, Helena E.
    Östberg, Therese
    Grundtman, Cecilia
    Glenmark, Birgitta
    Westerblad, Hakan
    IMPAIRED MYOFIBRILLAR FUNCTION IN SOLEUS MUSCLE OF MICE WITH COLLAGEN-INDUCED ARTHRITIS2009In: JOURNAL OF PHYSIOLOGICAL SCIENCES, ISSN 1880-6546, Vol. 59, p. 215-215Article in journal (Other academic)
  • 173. Yamada, Takashi
    et al.
    Place, Nicolas
    Kosterina, Natalia
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Östberg, Therese
    Zhang, Shi-Jin
    Grundtman, Cecilia
    Erlandsson-Harris, Helena
    Lundberg, Ingrid E.
    Glenmark, Birgitta
    Bruton, Joseph D.
    Westerblad, Hakan
    Impaired Myofibrillar Function in the Soleus Muscle of Mice With Collagen-Induced Arthritis2009In: Arthritis and Rheumatism, ISSN 0004-3591, E-ISSN 1529-0131, Vol. 60, no 11, p. 3280-3289Article in journal (Refereed)
    Abstract [en]

    Objective. Progressive muscle weakness is a common feature in patients with rheumatoid arthritis (RA). However, little is known about whether the intrinsic contractile properties of muscle fibers are affected in RA. This study was undertaken to investigate muscle contractility and the myoplasmic free Ca2+ concentration ([Ca2+](i)) in the soleus, a major postural muscle, in mice with collagen-induced arthritis (CIA). Methods. Muscle contractility and [Ca2+](i) were assessed in whole muscle and intact single-fiber preparations, respectively. The underlying mechanisms of contractile dysfunction were assessed by investigating redox modifications using Western blotting and antibodies against nitric oxide synthase (NOS), superoxide dismutase (SOD), 3-nitrotyrosine (3-NT), carbonyl, malondialdehyde (MDA), and S-nitrosocysteine (SNO-Cys). Results. The tetanic force per cross-sectional area was markedly decreased in the soleus muscle of mice with CIA, and the change was not due to a decrease in the amplitude of [Ca2+](i) transients. The reduction in force production was accompanied by slowing of the twitch contraction and relaxation and a decrease in the maximum shortening velocity. Immunoblot analyses showed a marked increase in neuronal NOS expression but not in inducible or endothelial NOS expression, which, together with the observed decrease in SOD2 expression, favors peroxynitrite formation. These changes were accompanied by increased 3-NT, carbonyl, and MDA adducts content in myofibrillar proteins from the muscles of mice with CIA. Moreover, there was a significant increase in SNO-Cys content in myosin heavy-chain and troponin I myofibrillar proteins from the soleus muscle of mice with CIA. Conclusion. These findings show impaired contractile function in the soleus muscle of mice with CIA and suggest that this abnormality is due to peroxynitrite-induced modifications in myofibrillar proteins.

  • 174. Yang, Likang
    et al.
    Duan, Fubin
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Analysis of the optimal design strategy of a magnetorheological smart structure2008In: Smart materials and structures (Print), ISSN 0964-1726, E-ISSN 1361-665X, Vol. 17, no 1Article in journal (Refereed)
    Abstract [en]

    The exploration of magnetorheological (MR) fluid applications involves many fields. During the phase of theory analysis and experimental investigations, most of the research has been in developing primary products, and the design method is becoming important in MR device design. To establish general design guidelines, not with the usual MR smart structure design method which just complies with the presented yield stress of smart materials, in this paper, an MR smart structure design method is presented according to the whole requirement of smart structure characteristics. In other words, the smart structure design method does not just execute its optimization according to the presented MR fluid features, and it can customize or select the properties of MR fluid obeying the whole system requirements. Besides the usual magnetic circuit design analysis, the MR fluid physical content, such as the volume fraction of particles, was incorporated into the design parameters of the products. At the same time, by utilizing the structural parameters, the response time of MR devices was considered by analyzing the time constant of electromagnetic coils inside the MR devices too. Additionally, the power consumption relevant to transient useful power was analyzed for structure design. Finally, based on the computation of the magnetic field in a finite element (COMSOL multiphysics), all these factors were illustrated in an MR fluid valve based on the results of a magnetic circuit design.

  • 175. Yunhua, L.
    et al.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    An alternative assumed strain method1999In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 178, no 1-2, p. 23-37Article in journal (Refereed)
    Abstract [en]

    In this paper, an Alternative Assumed Strain (AAS) method is put forward, on the basis of a previous work. The method has two main features: the stresses are eliminated from the finite element formulation by satisfying the stress-strain equations with the assumed strains, which is much more convenient than the L2-orthogonal condition in Enhanced Assumed Strain (EAS) method for developing finite elements; the stresses, obtained from the assumed strains with the stress-strain relations, are forced to satisfy the equilibrium equations identically to reduce the number of assumed strain parameters and to improve finite element efficiency. The method is applied to develop several variations of 3-node triangular and 4-node quadrilateral Mindlin plate elements. Numerical examples show that efficient elements could be obtained from the suggested method.

  • 176. Yunhua, L.
    et al.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Extension of field consistence approach into developing plane stress elements1999In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 173, no 1-2, p. 111-134Article in journal (Refereed)
    Abstract [en]

    In this research paper, the possibilities for extending the field consistence approach [L. Yunhua, On shear locking in finite elements, Licentiate Thesis, Stockholm, 1997; L. Yunhua, Explanation and elimination of shear locking and membrane locking with field consistence approach, Comput. Methods Appl. Mech. Engrg., in press], starting from different variational principles, to plane stress elements are investigated. In the extension, two main difficulties are: explicitly solving a set of coupled partial differential equations and satisfying inter-element compatibility. The first one is alleviated by constructing element interpolations from a set of quasi-general solutions, rather than the real general solutions, to the Euler-Lagrangian equations. The second one is solved by combining the field consistence approach with the iso-parametric interpolation technique. The traditional assumed stress method is improved and an efficient plane stress element is obtained. It seems that the relations between the three commonly used variational principles can be more reasonably established in the framework of the field consistence approach.

  • 177.
    Zhou, Yang
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Numerical instability investigations for thin membranes2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Membrane structures are commonly used in many fields. The studies of these structures are of increasing interest. The projects in this thesis focus on the evaluations of equilibrium states for pressurized membranes under different problem settings, using finite element methods, and the corresponding instability behaviors.

    The first part of the current work discusses the instability behavior of a thin, planar, circular and initially horizontal membrane subjected to downwards or upwards fluid pressure. The membrane structures exhibit large deformations under pressure. The method for evaluating fluid pressure from gravity was developed in finite element context, and used in numerical simulations. Limit and bifurcation points have been detected for different loading parameters and conditions. The effects on instabilities of parameters, the initial states of the membrane, and the chosen mesh are discussed.

    The second part of the current work discusses instability behavior of a thin, spherical and closed membrane containing gas and fluid, when placed on a horizontal rigid and non-friction plane. A multi-parametric loading is described. By adding practically relevant controlling equations, different classes of equilibrium paths were followed using a generalized path following algorithm. Stability conclusions were made, according to the considered load parameters and the constraints. A generalized eigenvalue analysis was used to evaluate the stability behavior including the constraint effects. Fold line evaluations were performed to analyze the parametric dependence. A solution surface approach is used to visualize the mechanical response under this multi-parametric setting.

    The third part of the current work focuses on instability response of a truncated sphere, containing gas and fluid, and in contact with two vertical rigid and non-friction planes. Different penalty formulations were used and compared. The effects of contact implementations on instability behaviors were investigated. Bifurcation points induced by contacts have been observed. Multi-parametric problems were defined, and generalized paths were followed. The multi-parametric stability was evaluated using generalized eigenvalue analysis, based on the mass and total differential matrices. The effects of augmenting equations on bifurcation points and limit points are discussed.

    The fourth part of the current work analyses the instability response of a truncated sphere, completely filled with fluid, placed on a horizontal plane and spinning around the vertical axis. The loads from fluid pressure and the constraints, e.g., fluid volume, were formulated to generate a symmetric differential matrix. Several mesh patterns with different symmetries were used to simulate the model, and the obtained results are compared. Various problem settings were considered, and generalized paths were followed. The effects of symmetry aspects of the chosen meshes on instability behaviors are discussed, as are the effects of parameters.

  • 178.
    Zhou, Yang
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Parametric stability analyses for fluid-loaded thin membranes2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Membrane structures are commonly used in many elds. The studies of thesestructures are of increasing interest. The two projects focus on the evaluations ofequilibrium states for uid-pressurized membranes under dierent loading conditions,and the corresponding instability behavior.The rst part of the current work discusses the instability behavior of a thin,planar, circular and initially horizontal membrane subjected to downwards or upwards uid pressure. The membrane structures exhibit large deformations under uid pressure. Various instability behaviors have been observed for dierent loadingparameters. Limit and bifurcation points have been detected for dierent loadingconditions. Dierent loading parameters have been used to interpret the instabilitybehavior. The eects on instability of parameters, the initial states of the membrane,and the chosen mesh have been discussed.The second part of the current work discusses instability behavior of a thin,spherical and closed membrane containing gas and uid placed on a horizontal rigidand non-friction plane. A multi-parametric loading has been described. By addingthe practically relevant controlling equations, the complex equilibrium paths werefollowed using the generalized path following algorithm, and the stability conclusionswere made dierently, according to the considered load parameters and theconstraints. A generalized eigenvalue analysis was used to evaluate the stabilitybehavior including the constraint eects. Fold line evaluations were performed toanalyze the parametric dependence of the instability behavior. A solution surfaceapproach was used to visualize the mechanical response under this multi-parametricsetting.

  • 179.
    Zhou, Yang
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Hussain, M.
    Guanglin, Kuang
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Zhang, J.
    Tu, Yaoquan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Mechanistic insights into peptide and ligand binding of the ATAD2-bromodomain via atomistic simulations disclosing a role of induced fit and conformational selection2018In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 36, p. 23222-23232Article in journal (Refereed)
    Abstract [en]

    ATAD2 has emerged as a promising bromodomain (BRD)-containing therapeutic drug target in multiple human cancers. However, recent druggability assessment studies predicted ATAD2's BRD as a target 'difficult to drug' because its binding pocket possesses structural features that are unfeasible for ligand binding. Here, by using all-atom molecular dynamics simulations and an advanced metadynamics method, we demonstrate a dynamic view of the binding pocket features which can hardly be obtained from the "static" crystal data. The most important features disclosed from our simulation data, include: (1) a distinct 'open-to-closed' conformational switch of the ZA loop region in the context of peptide or ligand binding, akin to the induced fit mechanism of molecular recognition, (2) a dynamic equilibrium of the BC loop "in" and "out" conformations, highlighting a role in the conformational selection mechanism for ligand binding, and (3) a new binding region identified distal to the histone-binding pocket that might have implications in bromodomain biology and in inhibitor development. Moreover, based on our simulation results, we propose a model for an "auto-regulatory" mechanism of ATAD2's BRD for histone binding. Overall, the results of this study will not only have implications in bromodomain biology but also provide a theoretical basis for the discovery of new ATAD2's BRD inhibitors.

  • 180.
    Zhou, Yang
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Nordmark, Arne
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Instability investigation for rotating thin spherical membrane2017In: International Journal of Non-Linear Mechanics, ISSN 0020-7462, E-ISSN 1878-5638, Vol. 97, p. 96-106Article in journal (Refereed)
    Abstract [en]

    A fluid-filled truncated spherical membrane fixed along its truncated edge to a horizontal, rigid and frictionless plane and spinning around a center axis was investigated. A two-parameter Mooney-Rivlin model was used to describe the material of the membrane. The truncated sphere was modeled in 3D using finite element meshes with different symmetry properties. A quadratic function was used for interpolating hydro-static pressure, giving a symmetric tangent stiffness matrix, thereby reproducing the conservative problem. Various problem settings were considered, related to the spinning, and different instability behaviors were observed. Multi-parametric problems were defined, generalized paths including primary and secondary paths were followed. Stability of the multi parametric problem was evaluated using generalized eigenvalue analysis based on the total differential matrix for the constrained problem. Numerical results showed that mesh symmetry affected the simulated stability behavior. Fold line evaluations showed the parametric effects on critical solutions.

  • 181.
    Zhou, Yang
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Nordmark, Arne
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Instability investigation for rotating thin spherical membranesManuscript (preprint) (Other academic)
  • 182.
    Zhou, Yang
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Nordmark, Arne
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Instability of thin circular membranes subjected to hydro-static loads2015In: International Journal of Non-Linear Mechanics, ISSN 0020-7462, E-ISSN 1878-5638, Vol. 76, p. 144-153Article in journal (Refereed)
    Abstract [en]

    Membrane structures subjected to hydrostatic load are prone to undergo large deformations and lose stability. This paper investigates different instability phenomena for a thin, circular and initially flat and horizontal membrane. The Mooney-Rivlin hyper-elastic model is used to provide the material description. An axisymmetric and a 3D model have been set up to show the large deformations and instability behavior with different parameter settings. Numerical examples show that the methods developed are capable to describe the deformation dependent loading conditions and the instability phenomena. The numerical simulations show fundamental differences in the response and instability behavior when the horizontal membrane is loaded from above or below. The parameters of fluids and membranes and the means for introducing the pressure are of essence for interpreting the instability behavior.

  • 183.
    Zhou, Yang
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Nordmark, Arne
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Multi-parametric stability investigation for gas and uid pressurized thin membranesManuscript (preprint) (Other academic)
  • 184.
    Zhou, Yang
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Nordmark, Arne
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Multi-parametric stability investigation for thin membranes with contactsManuscript (preprint) (Other academic)
  • 185.
    Zhou, Yang
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Nordmark, Arne
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Multi-parametric stability investigation for thin spherical membranes filled with gas and fluid2016In: International Journal of Non-Linear Mechanics, ISSN 0020-7462, E-ISSN 1878-5638, Vol. 82, p. 37-48Article in journal (Refereed)
    Abstract [en]

    The instability behavior of spherical membranes completely or partially filled with fluid, also with internal gas over-pressure, placed on a friction-less rigid plane was investigated. The two-parameter Mooney-Rivlin model was used for material description. A third order penalty function was used to describe the rigid support. Different problem settings were considered, and different instability responses were observed. For the partially fluid-filled membrane, a multi-parametric problem was defined and analyzed. Augmenting equations were introduced to impose control constraints on variables chosen. These equations also affect the instability analysis. A generalized eigenvalue analysis was used for the stability conclusions. Numerical simulations showed that appropriate control constraints are of essence to interpret the instability conclusions. Fold line evaluations were performed to analyze the dependence of the instability behavior on the parameters. A solution surface algorithm was utilized to analyze and visualize the mechanical responses to multi-variable loading.

  • 186.
    Zhou, Yang
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Nordmark, Arne
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Multi-parametric stability investigation for thin spherical membranes with contacts2017In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 131-132, p. 334-344Article in journal (Refereed)
    Abstract [en]

    The instability behavior for a thin truncated spherical membrane completely filled with fluid or containing both gas and fluid, fixed on a circular platform and in contact with two vertical planes was investigated. Different penalty functions for contacts, and symmetry aspects of the discretized model were studied, and gave effects on instability behavior. Stability conclusions for the multi-parametric problems were made using generalized eigenvalue analyses, showing limit points, bifurcation points and turning point. Contact conditions were shown to introduce bifurcations and secondary paths, dependent on the contact implementations and discretizations. Their effects on stability behaviors in connection with various controlling equations are discussed.

  • 187. Zolesi, V. S.
    et al.
    Ganga, P. L.
    Scolamiero, L.
    Micheletti, A.
    Podio-Guidugli, P.
    Tibert, Gunnar
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Donati, A.
    Ghiozzi, M.
    On an innovative deployment concept for large space structures2012In: 42nd International Conference on Environmental Systems 2012, ICES 2012, American Institute of Aeronautics and Astronautics, 2012Conference paper (Refereed)
    Abstract [en]

    Large deployable space structures are mission-critical technologies for which deployment failure cannot be an option. The difficulty to fully reproduce and test on ground the deployment of large systems dictates the need for extremely reliable architectural concepts. In 2010, ESA promoted a study focused at the pre-development of breakthrough architectural concepts offering superior reliability. The study, which was performed as an initiative of ESA Small Medium Enterprises Office (http://www.esa.int/SME/), by Kayser Italia at its premises in Livorno (Italy), with Universita' di Roma TorVergata (Rome, Italy) as sub-contractor and consultancy from KTH (Stockholm, Sweden), led to the identification of an innovative large deployable structure of "tensegrity" type, which achieves the required reliability because it permits a drastic reduction in the number of articulated joints in comparison with non-tensegrity architectures. The identified target application was in the field of large antenna reflectors. The project focused on the overall architecture of a deployable system and the related design implications. With a view toward verifying experimentally the performance of the deployable structure, a reduced-scale breadboard model was designed and manufactured. A gravity off-loading system was designed and implemented, so as to check deployment functionality in a 1-g environment. Finally, a test campaign was conducted, to validate the main design assumptions as well as to ensure the concept's suitability for the selected target application. The test activities demonstrated satisfactory stiffness, deployment repeatability, and geometric precision in the fully deployed configuration. The test data were also used to validate a finite element model, which predicts a good static and dynamic behavior of the full-scale deployable structure.

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