Energy Shaping Control of an Inverted Flexible Pendulum Fixed to a Cart

Control of compliant mechanical systems is increasingly being researched for several applications including flexible link robots and ultra-precision positioning systems. The control problem in these systems is challenging, especially with gravity coupling and large deformations, because of inherent underactuation and the combination of lumped and distributed parameters of a nonlinear system. In this paper we consider an ultra-flexible inverted pendulum on a cart and propose a new nonlinear energy shaping controller to keep the pendulum at the upward position with the cart stopped at a desired location. The design is based on a model, obtained via the constrained Lagrange formulation, which previously has been validated experimentally. The controller design consists of a partial feedback linearization step followed by a standard PID controller acting on two passive outputs. Boundedness of all signals and (local) asymptotic stability of the desired equilibrium is theoretically established. Simulations and experimental evidence assess the performance of the proposed controller.Comment: 11 pages, 7 figures, extended version of the NOLCOS 2016 pape

Extracting past-future vacuum correlations using circuit QED

We propose a realistic circuit QED experiment to test the extraction of past-future vacuum entanglement to a pair of superconducting qubits. The qubit P interacts with the quantum field along an open transmission line for an interval T_on and then, after a time-lapse T_off, the qubit F starts interacting for a time T_on in a symmetric fashion. After that, past-future quantum correlations will have transferred to the qubits, even if the qubits do not coexist at the same time. We show that this experiment can be realized with current technology and discuss its utility as a possible implementation of a quantum memory.Comment: 5 pages, 2 figures. v2: version accepted to Physical Review Letters. Title changed by editor

The secondary structure of apolipoprotein A-I on 9.6-nm reconstituted high-density lipoprotein determined by EPR spectroscopy.

Apolipoprotein A-I (ApoA-I) is the major protein component of high-density lipoprotein (HDL), and is critical for maintenance of cholesterol homeostasis. During reverse cholesterol transport, HDL transitions between an array of subclasses, differing in size and composition. This process requires ApoA-I to adapt to changes in the shape of the HDL particle, transiting from an apolipoprotein to a myriad of HDL subclass-specific conformations. Changes in ApoA-I structure cause alterations in HDL-specific enzyme and receptor-binding properties, and thereby direct the HDL particle through the reverse cholesterol transport pathway. In this study, we used site-directed spin label spectroscopy to examine the conformational details of the ApoA-I central domain on HDL. The motional dynamics and accessibility to hydrophobic/hydrophilic relaxation agents of ApoA-I residues 99-163 on 9.6-nm reconstituted HDL was analyzed by EPR. In previous analyses, we examined residues 6-98 and 164-238 (of ApoA-I's 243 residues), and combining these findings with the current results, we have generated a full-length map of the backbone structure of reconstituted HDL-associated ApoA-I. Remarkably, given that the majority of ApoA-I's length is composed of amphipathic helices, we have identified nonhelical residues, specifically the presence of a β-strand (residues 149-157). The significance of these nonhelical residues is discussed, along with the other features, in the context of ApoA-I function in contrast to recent models derived by other methods

Monetary policy implications of state-dependent prices and wages

En este trabajo estudiamos los efectos de las perturbaciones monetarias en un modelo donde las probabilidades de ajustar precios y salarios varían con el estado agregado e idiosincrásico debido a los «costes de control». Tanto las empresas al por menor como los trabajadores son competidores monopolísticos sujetos a perturbaciones idiosincrásicas en su productividad y a rigideces nominales. Las rigideces surgen porque tomar decisiones requiere tiempo, y más cuanto mayor sea su precisión. Esto impide que las empresas y los trabajadores ajusten precios y salarios sin error y en el momento justo. Simulamos el modelo seleccionando los parámetros de forma que reproduzca el tamaño y la frecuencia de los cambios en los precios y en los salarios observados en los datos. Los efectos reales de las perturbaciones monetarias son menos persistentes en nuestro marco «dependiente del estado» de lo que serían en un marco «dependiente del tiempo»no obstante, son de una magnitud similar a la observada en los datos macroeconómicos. La «no neutralidad» del dinero en nuestro modelo se debe, principalmente, a la rigidez de los salarios, más que a la de los precios. Cuando el nivel de rigidez nominal depende del estado de la economía, como en nuestro trabajo, la pendiente de la curva de Phillips disminuye cuanto menor es la inflación de largo plazo, ya que los ajustes nominales se hacen menos frecuentes y, por tanto, la inflación de corto plazo reacciona menos a las perturbaciones monetariasWe study the effects of monetary shocks in a model of state-dependent price and wage adjustment based on “control costs”. Suppliers of retail goods and of labor are both monopolistic competitors that face idiosyncratic productivity shocks and nominal rigidities. Stickiness arises because precise decisions are costly, so agents choose to tolerate small errors in the timing of adjustments. Our simulations are calibrated to microdata on the size and frequency of price and wage changes. Money shocks have less persistent real effects in our state-dependent model than they would a time-dependent framework, but nonetheless we obtain sufficient monetary nonneutrality for consistency with macroeconomic evidence. Nonneutrality is primarily driven by wage rigidity, rather than price rigidity. State-dependent nominal rigidity implies a flatter Phillips curve as trend inflation declines, because nominal adjustments become less frequent, making short-run inflation less reactive to shock

Creative clusters in Europe: a microdata approach

Creative industries are highly concentrated forming clusters. One of the main problems for the identification of clusters of creative industries in Europe is the lack of data, constrained in practice to regions (NUTS 2) and influenced by the heterogeneity in the definition of NUTS across countries. This research uses firm-level data geo-referenced at address level and geostatistical modeling to identify clusters of creative industries in fifteen European countries. The procedure is independent of administrative divisions and national boundaries and allows to produce a precise geography of the clusters of creative industries in Europe.

Light-matter decoupling and A2 term detection in superconducting circuits

APS March Meeting 2015, San Antonio, Texas, March 2–6, 2015We study the spontaneous emission of a qubit interacting with a one-dimensional waveguide through a realistic minimal-coupling interaction. We show that the diamagnetic term A2 leads to an effective decoupling of a single qubit from the electromagnetic field. This effect is observable at any range of qubit-photon couplings. For this we study a setup consisting of a transmon that is suspended over a transmission line. Assuming a standard model of qubit-line interaction, we prove that the relative strength of the A2 term is controlled with the qubit-line separation and show that, as a consequence, the spontaneous emission rate of the suspended transmon onto the line can increase with such separation, instead of decreasing.Peer Reviewe

Capacity Leasing in Cloud Systems using the OpenNebula Engine

Depto. de Arquitectura de Computadores y AutomáticaFac. de InformáticaTRUEUnión Europea. FP7Ministerio de Educación y Ciencia (MEC)Comunidad de Madridsubmitte

Dynamics for a 2-vertex Quantum Gravity Model

We use the recently introduced U(N) framework for loop quantum gravity to study the dynamics of spin network states on the simplest class of graphs: two vertices linked with an arbitrary number N of edges. Such graphs represent two regions, in and out, separated by a boundary surface. We study the algebraic structure of the Hilbert space of spin networks from the U(N) perspective. In particular, we describe the algebra of operators acting on that space and discuss their relation to the standard holonomy operator of loop quantum gravity. Furthermore, we show that it is possible to make the restriction to the isotropic/homogeneous sector of the model by imposing the invariance under a global U(N) symmetry. We then propose a U(N) invariant Hamiltonian operator and study the induced dynamics. Finally, we explore the analogies between this model and loop quantum cosmology and sketch some possible generalizations of it.Comment: 28 pages, v2: typos correcte

Do adolescents with impaired vision have different intentions and ambitions for their education, career and social outcomes compared to their peers? Findings from the Millennium Cohort Study

BACKGROUND/AIMS: To investigate if impaired vision adversely impacts the intentions/ambitions of adolescents concerning their future education, careers and social outcomes. METHODS: Population-based birth cohort study in the UK comprising 9273 participants from the Millennium Cohort Study who were followed up to age 17 years. Children were classified as having normal vision or unilateral or bilateral impaired vision caused by significant eye conditions based on detailed parental-structured questionnaire data on sight problems and treatment coded by clinicians. Ten domains covering education, career and social outcomes by age 30 were investigated. RESULTS: Adjusted regression models showed few differences by vision status. Bilateral impaired vision was associated with increased odds of intending to remain in full-time education after statutory school age (adjusted OR (aOR) 2.00, 95% CI 1.08 to 3.68) and of home ownership at age 30 (aOR 1.83, 95% CI 1.01 to 3.32). Impaired vision was not associated with intending to attend university. A significantly higher proportion of parents of children with bilateral or unilateral impaired vision thought that their child would not get the exam grades required to go to university than parents of those with normal vision (29% or 26% vs 16%, p=0.026). CONCLUSION: Adolescents with impaired vision have broadly the same intentions/ambitions regarding future education, careers and social outcomes as their peers with normal vision. The known significant gaps in attainment in these domains among young adults with vision impairment are therefore likely to be due to barriers that they face in achieving their ambitions. Improved implementation of existing interventions is necessary to ensure equality of opportunities