Generation of planar tensegrity structures through cellular multiplication

Tensegrity structures are frameworks in a stable self-equilibrated prestress state that have been applied in various fields in science and engineering. Research into tensegrity structures has resulted in reliable techniques for their form finding and analysis. However, most techniques address topology and form separately. This paper presents a bio-inspired approach for the combined topology identification and form finding of planar tensegrity structures. Tensegrity structures are generated using tensegrity cells (elementary stable self-stressed units that have been proven to compose any tensegrity structure) according to two multiplication mechanisms: cellular adhesion and fusion. Changes in the dimension of the self-stress space of the structure are found to depend on the number of adhesion and fusion steps conducted as well as on the interaction among the cells composing the system. A methodology for defining a basis of the self-stress space is also provided. Through the definition of the equilibrium shape, the number of nodes and members as well as the number of self-stress states, the cellular multiplication method can integrate design considerations, providing great flexibility and control over the tensegrity structure designed and opening the door to the development of a whole new realm of planar tensegrity systems with controllable characteristics.Comment: 29 pages, 19 figures, to appear at Applied Mathematical Modelin

Design of tensegrity structures using parametric analysis and stochastic search

Tensegrity structures are lightweight structures composed of cables in tension and struts in compression. Since tensegrity systems exhibit geometrically nonlinear behavior, finding optimal structural designs is difficult. This paper focuses on the use of stochastic search for the design of tensegrity systems. A pedestrian bridge made of square hollow-rope tensegrity ring modules is studied. Two design methods are compared in this paper. Both methods aim to find the minimal cost solution. The first method approximates current practice in design offices. More specifically, parametric analysis that is similar to a gradient-based optimization is used to identify good designs. Parametric studies are executed for each system parameter in order to identify its influence on response. The second method uses a stochastic search strategy called probabilistic global search Lausanne. Both methods provide feasible configurations that meet civil engineering criteria of safety and serviceability. Parametric studies also help in defining search parameters such as appropriate penalty costs to enforce constraints while optimizing using stochastic search. Traditional design methods are useful to gain an understanding of structural behavior. However, due to the many local minima in the solution space, stochastic search strategies find better solutions than parametric studie

Untersuchungen zur LDL-Rezeptoraktivität des Karpfen (Cyprinus carpio L.)

Die vorliegende Arbeit beinhaltet die Charakterisierung des LDL-Rezeptors von Vertretern verschiedener Wirbeltierklassen mit besonderem Schwerpunkt auf Untersuchungen am Karpfen (Cyprinus carpio). Zusätzlich wurden Präparationen von Lipoproteinen geringer Dichte (LDL) von Mensch, Forelle und Karpfen auf ihre Bindungsfähigkeit an Geweben von Mensch, Rind, Forelle und Karpfen überprüft. Entgegen den Angaben von Fainaru et al. (Comp Biochem Physiol [B]. 1988; 91: 331-338) konnte eine spezifische Bindung von Human-LDL weder an Lebermembranen des Karpfen, noch an Lebermembranen der Forelle nachgewiesen werden. Auch für Forellen-LDL konnte eine spezifische Bindung an Human-Lebermembranen nicht gezeigt werden. Dagegen wurden die oben genannten LDL-Präparationen von den untersuchten Membrantypen der verschiedenen Wirbeltierspezies rezeptor-vermittelt gebunden. Prinzipiell binden LDL von Fischen mit niedrigerer Affinität als Säuger-LDL an Säuger-Membranpräparationen und umgekehrt. Die Untersuchungen wurden von einer kritischen Analyse der Methoden der Proteinbestimmung nach Lowry und der Auswertung von Rezeptorbindungsstudien begleitet, zu deren objektiven Durchführung zwei Computerprogramme entwickelt wurden

Cellular morphogenesis of three-dimensional tensegrity structures

The topology and form finding of tensegrity structures have been studied extensively since the introduction of the tensegrity concept. However, most of these studies address topology and form separately, where the former represented a research focus of rigidity theory and graph theory, while the latter attracted the attention of structural engineers. In this paper, a biomimetic approach for the combined topology and form finding of spatial tensegrity systems is introduced. Tensegrity cells, elementary infinitesimally rigid self-stressed structures that have been proven to compose any tensegrity, are used to generate more complex tensegrity structures through the morphogenesis mechanisms of adhesion and fusion. A methodology for constructing a basis to describe the self-stress space is also provided. Through the definition of self-stress, the cellular morphogenesis method can integrate design considerations, such as a desired shape or number of nodes and members, providing great flexibility and control over the tensegrity structure generated.Comment: 31 pages, 17 figure

Design of tensegrity structures using parametric analysis and stochastic search.

The final publication is available at Springer via http://dx.doi.org/10.1007/s00366-009-0154-1Tensegrity structures are lightweight structures composed of cables in tension and struts in compression. Since tensegrity systems exhibit geometrically nonlinear behavior, finding optimal structural designs is difficult. This paper focuses on the use of stochastic search for the design of tensegrity systems. A pedestrian bridge made of square hollow-rope tensegrity ring modules is studied. Two design methods are compared in this paper. Both methods aim to find the minimal cost solution. The first method approximates current practice in design offices. More specifically, parametric analysis that is similar to a gradient-based optimization is used to identify good designs. Parametric studies are executed for each system parameter in order to identify its influence on response. The second method uses a stochastic search strategy called probabilistic global search Lausanne. Both methods provide feasible configurations that meet civil engineering criteria of safety and serviceability. Parametric studies also help in defining search parameters such as appropriate penalty costs to enforce constraints while optimizing using stochastic search. Traditional design methods are useful to gain an understanding of structural behavior. However, due to the many local minima in the solution space, stochastic search strategies find better solutions than parametric studies.Swiss National Science Foundatio

Analysis of self-equilibrated networks through cellular modeling

Network equilibrium models represent a versatile tool for the analysis of interconnected objects and their relationships. They have been widely employed in both science and engineering to study the behavior of complex systems under various conditions, including external perturbations and damage. In this paper, network equilibrium models are revisited through graph-theory laws and attributes with special focus on systems that can sustain equilibrium in the absence of external perturbations (self-equilibrium). A new approach for the analysis of self-equilibrated networks is proposed; they are modeled as a collection of cells, predefined elementary network units that have been mathematically shown to compose any self-equilibrated network. Consequently, the equilibrium state of complex self-equilibrated systems can be obtained through the study of individual cell equilibria and their interactions. A series of examples that highlight the flexibility of network equilibrium models are included in the paper. The examples attest how the proposed approach, which combines topological as well as geometrical considerations, can be used to decipher the state of complex systems.Comment: 38 pages, 23 figure

Resilienz durch soziale Innovation: Erfolgsfaktoren und Barrieren von sozialen Innovationen in der Stadtregion Bern

Soziale Innovationen, definiert als neue Lösungen für soziale Probleme, können zur Resilienz einer Gesellschaft beitragen. Damit deren Potenzial genutzt werden kann, gilt es jedoch, die Erfolgsfaktoren und Barrieren bei der Umsetzung von sozialen Innovationen zu verstehen. Dieser Beitrag untersucht deshalb im Rahmen einer Interviewstudie die Erfolgsfaktoren und Barrieren für soziale Innovationen im Raum Bern und stellt heraus, wie konkret zur Förderung von sozialen Innovationen beigetragen werden kann