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In this paper, we analyze a mass-spring-friction oscillator with the friction modeled by a regularized stiction model. We do so in the limit where the ratio of the natural spring frequency and the forcing frequency is on the same order of magnitude as the scale associated with the regularized stiction model. The motivation for studying this special parameter regime (which can be interpreted as a rigid body limit) comes from [E. Bossolini, M. Br{\e}ns, and K. U. Kristiansen, SIAM J. Appl. Dyn. Syst., 16, (2017), pp. 2233-2258] which demonstrated new friction phenomena in this regime. The results of this paper led to some open problems; see also [E. Bossolini, M. Br{\e}ns, and K. U. Kristiansen, SIAM Rev., 62 (2020), pp. 869-897], that we resolve in this paper. In particular, using GSPT and blowup [C. K. R. T. Jones, in Dynamical Systems, Lecture Notes in Math. 1609, Springer, Berlin, 1995, pp. 44-118; M. Krupa and P. Szmolyan, SIAM J. Math. Anal., 33, (2001), pp. 286-314], we provide a simple geometric description of the bifurcation of stick-slip limit cycles through a combination of a canard and a global return mechanism. We also show that this combination leads to a canard-based horseshoe and are therefore able to prove existence of chaos in this fundamental oscillator system. [ABSTRACT FROM AUTHOR]

For a positive integer k, a radio k-coloring of a simple connected graph G = (V(G), E(G)) is a mapping f : V (G) → { 0 , 1 , 2 , ... } such that | f (u) - f (v) | ≥ k + 1 - d (u , v) for each pair of distinct vertices u and v of G, where d(u, v) is the distance between u and v in G. The span of a radio k-coloring f, rck(f), is the maximum integer assigned by it to some vertex of G. The radio k-chromatic number, rck(G) of G is min{rck(f)}, where the minimum is taken over all radio k-colorings f of G. If k is the diameter of G, then rck(G) is known as the radio number of G. In this paper, we propose an improved upper bound of radio k-chromatic number for a given graph against the other which is due to Saha and Panigrahi (in: Arumugan, Smyth (eds) Combinatorial algorithms (IWOCA 2012). Lecure notes in computer science, vol 7643, Springer, Berlin, 2012). The computational study shows that the proposed algorithm overcomes the previous algorithm. We introduce a polynomial algorithm [differs from the other that is due to Liu and Zhu (SIAM J Discrete Math 19(3):610–621, 2005)] which determines the radio number of the path graph Pn. Finally, we propose a new integer linear programming model for the radio k-coloring problem. The computational study between the proposed algorithm and LINGO solver shows that the proposed algorithm overcomes LINGO solver. [ABSTRACT FROM AUTHOR]