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In this work, we discuss the controllability and observability behaviors of a non-homogeneous conformable fractional dynamical system (C-FDS) based on the conformable fractional exponential matrix (C-FEM) and fractional Grammian matrix (FGM). Moreover, the nice relationships between controllability, observability, and stability for non-homogeneous C-FDS are derived. To demonstrate the effectiveness of our obtained results, we present the general solutions (GSs), controllability, observabilities and stabilities to three attractive physical and engineering problems related to compatibility with conformable fractional electrical circuits (C-FECs). Finally, the fractional and classical behaviors of each problem have been covered, respectively, when α = 1 2 and α = 1 .

We consider nonlinear electrical circuits for which we derive a port-Hamiltonian formulation. After recalling a framework for nonlinear port-Hamiltonian systems, we model each circuit component as an individual port-Hamiltonian system. The overall circuit model is then derived by considering a port-Hamiltonian interconnection of the components. We further compare this modeling approach with standard formulations of nonlinear electrical circuits.

This paper is on tilings of polygons by rectangles. A celebrated physical interpretation of such tilings due to R.L. Brooks, C.A.B. Smith, A.H. Stone and W.T. Tutte uses direct-current circuits. The new approach of the paper is an application of alternating-current circuits. The following results are obtained: - a necessary condition for a rectangle to be tilable by rectangles of given shapes; - a criterion for a rectangle to be tilable by rectangles similar to it but not all homothetic to it; - a criterion for a generic polygon to be tilable by squares. These results generalize the ones of C. Freiling, R. Kenyon, M. Laczkovich, D. Rinne and G. Szekeres., Comment: In English and in Russian; 21 pages; 6 figures; minor improvement of exposition, Russian translation added

A simple discrete planar dynamical model for the ideal (logical) R-S flip-flop circuit is developed with an eye toward mimicking the dynamical behavior observed for actual physical realizations of this circuit. It is shown that the model exhibits most of the qualitative features ascribed to the R-S flip-flop circuit, such as an intrinsic instability associated with unit set and reset inputs, manifested in a chaotic sequence of output states that tend to oscillate among all possible output states, and the existence of periodic orbits of arbitrarily high period that depend on the various intrinsic system parameters. The investigation involves a combination of analytical methods from the modern theory of discrete dynamical systems, and numerical simulations that illustrate the dazzling array of dynamics that can be generated by the model. Validation of the discrete model is accomplished by comparison with certain Poincar\'e map like representations of the dynamics corresponding to three-dimensional differential equation models of electrical circuits that produce R-S flip-flop behavior., Comment: Accepted Feb 23, 2009

A polynomial P in n complex variables is said to have the "half-plane property" (or Hurwitz property) if it is nonvanishing whenever all the variables lie in the open right half-plane. Such polynomials arise in combinatorics, reliability theory, electrical circuit theory and statistical mechanics. A particularly important case is when the polynomial is homogeneous and multiaffine: then it is the (weighted) generating polynomial of an r-uniform set system. We prove that the support (set of nonzero coefficients) of a homogeneous multiaffine polynomial with the half-plane property is necessarily the set of bases of a matroid. Conversely, we ask: For which matroids M does the basis generating polynomial P_{B(M)} have the half-plane property? Not all matroids have the half-plane property, but we find large classes that do: all sixth-root-of-unity matroids, and a subclass of transversal (or cotransversal) matroids that we call "nice". Furthermore, the class of matroids with the half-plane property is closed under minors, duality, direct sums, 2-sums, series and parallel connection, full-rank matroid union, and some special cases of principal truncation, principal extension, principal cotruncation and principal coextension. Our positive results depend on two distinct (and apparently unrelated) methods for constructing polynomials with the half-plane property: a determinant construction (exploiting "energy" arguments), and a permanent construction (exploiting the Heilmann-Lieb theorem on matching polynomials). We conclude with a list of open questions., Comment: LaTeX2e, 111 pages. Submission includes Mathematica programs niceprincipal.m and nicetransversal.m Version 2 corrects a small error at the beginning of Appendix B, and makes a few small improvements elsewhere. To appear in Advances in Applied Mathematics

In an alternating-current network, each edge has a complex "conductance" with positive real part. The response map is the linear map from the vector of voltages at a subset of "boundary nodes" to the vector of currents flowing into the network through these nodes. We prove that the known necessary conditions for these response maps are sufficient, and we construct an appropriate alternating-current network for a given response map., Comment: 6 pages, 1 figure