In-plane thermoelectric power of untwinned YBa sub 2 Cu sub 3 O sub 7 minus. delta

We present the first measurements of the temperature and oxygen-doping dependences of thermoelectric power in the {ital ab} plane of untwinned YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} ({delta}{approx}0.10) for {ital T}{le}330 K. Employing a two-band model and measured electrical resistivities, we derive the chain and plane components of the thermopower, {ital S}{sub ch} and {ital S}{sub pl}. The behavior of {ital S}{sub ch} indicates that some of the chain conduction occurs via carriers in a narrow band. {ital S}{sub pl}({ital T}) is similar to the in-plane thermopower of the other cuprates, suggesting a universal'' behavior for the CuO{sub 2} planes. The results are discussed with reference to the known Fermi surface

Optimal topology and geometry for controllable tensegrity systems

This paper demonstrates a procedure to design an optimal mass to stiffness ratio tensegrity structure. Starting from an initial layout of the structure that defines an allowed set of element connections, the procedure defines positions of the nodal points of the structure, volumes of the elements and their rest lengths yielding a tensegrity structure having smaller compliance for a given load applied then an initial design. To satisfy design requirements strength constraint for all the elements of the structure, buckling constraint for bar elements as well as constraint on geometry of the structure are imposed yielding a nonconvex nonlinear constrained optimization problem. Structural static response is computed using complete nonlinear large displacement model. Examples showing optimal layout of a 2D and 3D structure are shown