On the determination of constitutive parametersin a hyperelastic model for a soft tissue

The aim of this paper is to study a model of hyperelastic materials and itsapplications into soft tissue mechanics. In particular, we first determine an unbounded domain of the constitutive parameters of the model making our smoothstrain energy function to be polyconvex and hence satisfying the Legendre–Hadamard condition. Thus, physically reasonable material behaviour are described by our model with these parameters and a plently of tissues can betreated. Furthermore, we localize bounded subsets of constitutive parameters in fixed physical and very general bounds and then introduce a family of descrete stress–strain curves. Whence, various classes of tissues are characterized. Ourgeneral approach is based on a detailed analytical study of the first Piola–Kirchhoff stress tensor through its dependence on the invariants and on the constitutive parameters. The uniqueness of parameters for one tissue is discussed by introducing the notion of manifold of constitutive parameters, whichis locally represented by possibly different physical quantities. The advantage of our study is that we show a possible way to improve of the usual approachesshown in the literature which are mainly based on the minimization of a costfunction as the difference between experimental and model results

Experimental Validation of Optical Simulation for Complex Building Integrated Photovoltaic System.

Simulation of BIPV system performance is usually based on a Plane-Of-Array method, adopted from classical PV plant systems, to estimate power generation. This methods is very limited for simulating facades in complex urban environments, such as dense urban areas, as it uses simplified near-field shading to estimate system losses. Furthermore, this approach accounts only for PV electricity yield generation, while neglecting other architectural criteria like daylighting, especially important in case of semi transparent PV facade. For the purposes of complex BIPV facades, other methods, such as ray tracing, are more preferable. Therefore, this research aims to estimate capabilities and accuracy of RADIANCE ray tracing engine to calculate daylighting and irradiance on PV surface. Validation procedure has been carried out for complex BIPV façade module, composed of complex profiled glass tile and semi-transparent Dye-Sensitized Solar Cells. Results showed reasonably good agreement between simulation and experimental measurements, which proves that method is capable for being used for the general purposes of complex BIPV systems

Asynchronous Computation of Tube-based Model Predictive Control

Tube-based model predictive control (MPC) methods bound deviations from a nominal trajectory due to uncertainties in order to ensure constraint satisfaction. While techniques that compute the tubes online reduce conservativeness and increase performance, they suffer from high and potentially prohibitive computational complexity. This paper presents an asynchronous computation mechanism for system level tube-MPC (SLTMPC), a recently proposed tube-based MPC method which optimizes over both the nominal trajectory and the tubes. Computations are split into a primary and a secondary process, computing the nominal trajectory and the tubes, respectively. This enables running the primary process at a high frequency and moving the computationally complex tube computations to the secondary process. We show that the secondary process can continuously update the tubes, while retaining recursive feasibility and robust stability of the primary process.Comment: Submitted to IFAC WC 202

Zero-Order Optimization for Gaussian Process-based Model Predictive Control

By enabling constraint-aware online model adaptation, model predictive control using Gaussian process (GP) regression has exhibited impressive performance in real-world applications and received considerable attention in the learning-based control community. Yet, solving the resulting optimal control problem in real-time generally remains a major challenge, due to i) the increased number of augmented states in the optimization problem, as well as ii) computationally expensive evaluations of the posterior mean and covariance and their respective derivatives. To tackle these challenges, we employ i) a tailored Jacobian approximation in a sequential quadratic programming (SQP) approach, and combine it with ii) a parallelizable GP inference and automatic differentiation framework. Reducing the numerical complexity with respect to the state dimension $n_x$ for each SQP iteration from $\mathcal{O}(n_x^6)$ to $\mathcal{O}(n_x^3)$, and accelerating GP evaluations on a graphical processing unit, the proposed algorithm computes suboptimal, yet feasible solutions at drastically reduced computation times and exhibits favorable local convergence properties. Numerical experiments verify the scaling properties and investigate the runtime distribution across different parts of the algorithm.Comment: accepted for European Journal of Control (EJC), ECC 2023 Special Issu

Innovative Cable Net Curved-Glass Photovoltaic Façade

Building Integrated PhotoVoltaic (BIPV) facades have been present for decades in various forms and building application types. However, they have not yet reached their potential due to the strict technical PhotoVoltaic (PV) requirements, the design and simulation complexity, as well as their limited aesthetics, demonstrated by a lack of visual innovation and customization in comparison with other building elements. The main objective of this paper is to improve both overall visual effect and building performance through an integrated solar design approach. In order to address these requirements, this paper presents an innovative performance-based design methodology for a BIPV façade. The approach uses parametric design framework to define a typological set of BIPV modules, each with its particular performances, allowing module and performance variation across a façade surface. Therefore, each module can take a specific position in respect to the urban settings and indoor requirements, in order to optimize and improve the overall performance. Moreover, design criteria are not compromised, as this innovative methodology takes into account variable requirements with unique design system that lead to the consistent appearance, and embrace a paneling customization with just a small set of BIPV modules. This design concept has been demonstrated on a curved-glass BIPV façade that is mounted on a cable-net structure. The result is a high-performance optically dynamic façade, with a smooth and curvy appearance

Conformal couplings of a scalar field to higher curvature terms

We present a simple way of constructing conformal couplings of a scalar field to higher order Euler densities. This is done by constructing a four-rank tensor involving the curvature and derivatives of the field, which transforms covariantly under local Weyl rescalings. The equation of motion for the field, as well as its energy momentum tensor are shown to be of second order. The field equations for the spherically symmetric ansatz are integrated, and for generic non-homogeneous couplings, the solution is given in terms of a polynomial equation, in close analogy with Lovelock theories.Comment: 9 pages, no figures. Based on a talk given by one of the authors at Centro de Estudios Cientificos, Valdivia, Chile, on June 22, 2011. V2: 11 pages, no figures. Typos fixed, appendices and references added. v3: to appear in CQ

Water activated ionic conduction in cross-linked polyelectrolytes

The electrical properties of polyelectrolytes depend on the water concentration of the environment. The behaviour of both conductance and capacitance caused by variations in relative humidity and temperature was investigated by impedance spectroscopy for humidity sensors based on an interpenetrated network of a polymer and a polyelectrolyte. The results were interpreted on the base of the Langmuir and Kelvin equations and two different sensing mechanisms were highlighted for low and high water content

de Sitter black hole with a conformally coupled scalar field in four dimensions

A four-dimensional black hole solution of the Einstein equations with a positive cosmological constant, coupled to a conformal scalar field, is given. There is a curvature singularity at the origin, and scalar field diverges inside the event horizon. The electrically charged solution, which has a fixed charge-to-mass ratio is also found. The quartic self-interacting coupling becomes bounded in terms of Newton's and the cosmological constants.Comment: 5 pages, no figures, CECS style, energy conditions are discussed and some references were added. To appear in Phys. Rev.

Topological Invariants, Instantons and Chiral Anomaly on Spaces with Torsion

In a spacetime with nonvanishing torsion there can occur topologically stable configurations associated with the frame bundle which are independent of the curvature. The relevant topological invariants are integrals of local scalar densities first discussed by Nieh and Yan (N-Y). In four dimensions, the N-Y form $N= (T^a \wedge T_a - R_{ab} \wedge e^a \wedge e^b)$ is the only closed 4-form invariant under local Lorentz rotations associated with the torsion of the manifold. The integral of $N$ over a compact D-dimensional (Euclidean) manifold is shown to be a topological invariant related to the Pontryagin classes of SO(D+1) and SO(D). An explicit example of a topologically nontrivial configuration carrying nonvanishing instanton number proportional to $\int N$ is costructed. The chiral anomaly in a four-dimensional spacetime with torsion is also shown to contain a contribution proportional to $N$, besides the usual Pontryagin density related to the spacetime curvature. The violation of chiral symmetry can thus depend on the instanton number of the tangent frame bundle of the manifold. Similar invariants can be constructed in D>4 dimensions and the existence of the corresponding nontrivial excitations is also discussed.Comment: 6 pages, RevTeX, no figures, two column

Management Control, International Observatory 2012

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