On global properties of passivity-based control of an inverted pendulum,”

SUMMARY The paper adresses the problem of stabilization of a speci"c target position of underactuated Lagrangian or Hamiltonian systems. We propose to solve the problem in two steps: "rst to stabilize a set with the target position being a limit point for all trajectories originating in this set and then to switch to a locally stabilizing controller. We illustrate this approach by the well-known example of inverted pendulum on a cart. Particularly, we design a controller which makes the upright position of the pendulum and zero displacement of the cart a limit point for almost all trajectories. We derive a family of static feedbacks such that any solution of the closed loop system except for those originating on some two-dimensional manifold approaches an arbitrarily small neighbourhood of the target position. The proposed technique is based on the passivity properties of the inverted pendulum. A possible extension to a more general class of underactuated mechanical systems is discussed

Institute of intellectual property in the context of the Russian innovative system development

Objective: to identify the main features of the impact of the intellectual property institute on the Russian innovation system development using the analysis of theoretical studies and narratives on the impact of intellectual property on innovations.Methods: qualitative methods of analysis of institutions (narrative analysis), analysis of statistical data.Results: the difference between the traditional, mixed and heterodox approaches to substantiating or criticizing the intellectual property institute is shown. To illustrate the ideas of each of the selected approaches, relevant examples of narratives are given, which describe the impact of intellectual property on innovative activity. Based on the study of the global experience in overcoming problems related to intellectual property, it is shown that many countries have long been taking measures to limit the validity of foreign patents in order to support the innovative activity of national enterprises. The analysis of narratives also demonstrates the existence of a typical narrative about the rejection of international patents in the field of medicines production and medical technologies, justified by the state’s concern for the health and safety of the population. Scientific novelty: it consists in applying the methodology of narrative economics to the analysis of intellectual property and its role in the Russian innovation system.Practical significance: the main provisions of the article can be used to review the inefficiency of the existing intellectual property institute and to propose promising ways to reform it

Structural Properties of Self-Attracting Walks

Self-attracting walks (SATW) with attractive interaction u > 0 display a swelling-collapse transition at a critical u_{\mathrm{c}} for dimensions d >= 2, analogous to the \Theta transition of polymers. We are interested in the structure of the clusters generated by SATW below u_{\mathrm{c}} (swollen walk), above u_{\mathrm{c}} (collapsed walk), and at u_{\mathrm{c}}, which can be characterized by the fractal dimensions of the clusters d_{\mathrm{f}} and their interface d_{\mathrm{I}}. Using scaling arguments and Monte Carlo simulations, we find that for u<u_{\mathrm{c}}, the structures are in the universality class of clusters generated by simple random walks. For u>u_{\mathrm{c}}, the clusters are compact, i.e. d_{\mathrm{f}}=d and d_{\mathrm{I}}=d-1. At u_{\mathrm{c}}, the SATW is in a new universality class. The clusters are compact in both d=2 and d=3, but their interface is fractal: d_{\mathrm{I}}=1.50\pm0.01 and 2.73\pm0.03 in d=2 and d=3, respectively. In d=1, where the walk is collapsed for all u and no swelling-collapse transition exists, we derive analytical expressions for the average number of visited sites and the mean time to visit S sites.Comment: 15 pages, 8 postscript figures, submitted to Phys. Rev.

Mechanism of Translation Inhibition by Type II GNAT Toxin AtaT2

Type II toxin-antitoxins systems are widespread in prokaryotic genomes. Typically, they comprise two proteins, a toxin, and an antitoxin, encoded by adjacent genes and forming a complex in which the enzymatic activity of the toxin is inhibited. Under stress conditions, the antitoxin is degraded liberating the active toxin. Though thousands of various toxin-antitoxins pairs have been predicted bioinformatically, only a handful has been thoroughly characterized. Here, we describe the AtaT2 toxin from a toxin-antitoxin system from Escherichia coli O157:H7. We show that AtaT2 is the first GNAT (Gcn5-related N-acetyltransferase) toxin that specifically targets charged glycyl tRNA. In vivo, the AtaT2 activity induces ribosome stalling at all four glycyl codons but does not evoke a stringent response. In vitro, AtaT2 acetylates the aminoacyl moiety of isoaccepting glycyl tRNAs, thus precluding their participation in translation. Our study broadens the known target specificity of GNAT toxins beyond the earlier described isoleucine and formyl methionine tRNAs, and suggest that various GNAT toxins may have evolved to specifically target other if not all individual aminoacyl tRNAs

Review and Unification of Methods for Computing Derivatives of Multidisciplinary Systems

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97061/1/AIAA2012-1589.pd

Comparing one-shot and multi-shot methods for solving periodic of Riccati differential equations

Abstract - One-shot methods and recently proposed multi-shot methods for computing stabilizing solutions of continuoustime periodic Riccati differential equations are examined and evaluated on two test problems. The first problem arises from a stabilization problem for an artificially constructed time-varying linear systems for which the exact solution is known. The second problem originates from a nonlinear stabilization problem for numercial comparisons have been performed using both general purpose and symplectic integration methods for solving the associated Hamiltontian differential systems. In the multi-shot method a stable subspace is determined using recently published algorithms for computing a reodered periodic real Schur form. The obtained results show the increased accuracy achievable by combining multi-shot methods with structure preserving (symplectic) integration techniques

ADOL-F Automatic Differentiation of Fortran Codes

The package ADOL--F described here is a Fortran 90 interface to the ADOL--C library and facilitates the evaluation of first and higher derivatives of vector functions that are defined by computer programs written in Fortran 90/77. The numerical values of derivative vectors are obtained free of truncation errors at a small multiple of the run time and randomly accessed memory of the given function evaluation program. Derivative matrices are obtained by columns or rows. For solution curves defined by ordinary differential equations, special routines are provided that evaluate the Taylor coefficient vectors and their Jacobians with respect to the current state vector. The derivative calculations involve a possibly substantial (but always predictable) amount of data that are accessed strictly sequentially and are therefore automatically paged out to external files. 1 Introduction Automatic differentiation [4, 9] is a non-approximative method just like symbolic differentiation and allows f..