Recursive Thick Modeling and the Choice of Monetary Policy in Mexico.

The choice of monetary policy is the most important concern of central banks. However, this choice is always confronted, inter alia, with two relevant aspects of economic policy: parameter instability and model uncertainty. This paper deals with both types of uncertainty using a very specific class of models in an optimal control framework. For optimal policy rates series featuring the first two moments similar to those of the actual nominal interest rates in Mexico, we show that recursive thick modeling gives a better approximation than recursive thin modeling. We complement previous work by evaluating the usefulness of both recursive thick modeling and recursive thin modeling in terms of direction-of-change forecastability.Macroeconomic policy, Model uncertainty, Optimal control, Monetary policy, Inflation targeting

Frequency support characteristics of grid-interactive power converters based on the synchronous power controller

Grid-interactive converters with primary frequency control and inertia emulation have emerged and are promising for future renewable generation plants because of the contribution in power system stabilization. This paper gives a synchronous active power control solution for gridinteractive converters , as a way to emulate synchronous generators for inerita characteristics and load sharing. As design considerations, the virtual angle stability and transient response are both analyzed, and the detailed implementation structure is also given without entailing any difficulty in practice. The analytical and experimental validation of frequency support characteristics differentiates the work from other publications on generator emulation control. The 10 kW simulation and experimental frequency sweep tests on a regenerative source test bed present good performance of the proposed control in showing inertia and droop characteristics, as well as the controllable transient response.Peer ReviewedPostprint (author's final draft

Analysis of the Performance of Mexican Pension Funds: Evidence from a Stationary Bootstrap Application

This paper assesses the performance of Mexican pension funds (AFORES) by using an asset pricing model that includes macroeconomic factors and benchmark portfolios to explain returns. We apply a bootstrap statistical technique to obtain the cross-sectional distribution of performance measures (alphas) across all pension funds. This is done to determine whether a pension fund manager adds value to the portfolio before commissions charges, or if the performance observed, after controlling for the relevant factors, is simply explained by luck. Moreover, by comparing pension fund alphas to the distributions of alphas corresponding to lower rankings, we can find out if a particular fund statistically distinguishes itself from others. Our results provide evidence that pension funds managers do not add value to the portfolio and that funds are not distinguishable from each other.Pension funds, Performance evaluation, Stationary bootstrap

Meanings of fractions as demonstrated by future primary teachers in the initial phase of teacher education

Fractions are a fundamental content of primary-level education and must therefore be included in the training courses for primary school teachers. Experts argue that deep understanding is required to improve primary school teachers’ knowledge of this mathematical concept (Ball, 1990; Cramer, Post & del Mas, 2002; Newton, 2008). Our study focuses on the part-whole relationship as a crucial foundation in working with fractions. This paper characterizes some of the meanings of this relationship for a group of future primary school teachers

Meaning of the part-whole relation and the concept of fraction for primary teachers

The part-whole relation is complex and raises questions that affect different disciplines. Researchers have proposed different interpretations of the notions of fraction and rational number (e.g., Behr, Lesh, Post & Silver, 1983; Kieren, 1976). We highlight three kinds of relations in the study of rational numbers—the part whole-relation, the part-part relation, and the functional relation—through which we organize the different subconstructs of rational number. We claim that the meaning of fractions should be understood through three components: their mathematical structure, their representations and their senses

Start-up of virtual synchronous machine: methods and experimental comparison

A modern grid is smarter mainly in the advance in information and communication technologies, while the power processing mechanism does not make a big difference. To make a modern grid smarter, the grid control should be improved to process the power in a smarter way. Therefore, it is easily foreseen that virtual synchronous machines, which emulates the synchronous machines based on power converters, may have big potentials in a future energy internet. This paper uses the Synchronous Power Controller with emulated and improved synchronous machine characteristics for renewable generation systems and proposes two start-up strategies. The proposed strategies are explained in detail, verified and compared by experimental results.Peer ReviewedPostprint (published version

Dynamics estimation and generalized tuning of stationary frame current controller for grid-tied power converters

The integration of AC-DC power converters to manage the connection of generation to the grid has increased exponentially over the last years. PV or wind generation plants are one of the main applications showing this trend. High power converters are increasingly installed for integrating the renewables in a larger scale. The control design for these converters becomes more challenging due to the reduced control bandwidth and increased complexity in the grid connection filter. A generalized and optimized control tuning approach for converters becomes more favored. This paper proposes an algorithm for estimating the dynamic performance of the stationary frame current controllers, and based on it a generalized and optimized tuning approach is developed. The experience-based specifications of the tuning inputs are not necessary through the tuning approach. Simulation and experimental results in different scenarios are shown to evaluate the proposal.Peer ReviewedPostprint (published version

Examining the structure of ideas of reference in clinical and community samples

Aims: This study addresses the psychometric properties of a Spanish validation of the REF scale of ideas of reference (IRs) in detecting and following at-risk mental states and psychosis. Methods: A total of 9447 participants were distributed in three groups: 676 patients with various diagnoses-154 with psychotic disorders, 6291 youths aged 11 to 20, and 2480 adult participants aged 21 to 84. Results: Youths had higher scores than adults on IRs, observing a progressive decrease and stabilization in the twenties. Exploratory factor analysis provided a structure for the overall IRs score, with five first-order dimensions and one second-order dimension. Confirmatory factor analysis supported the structure with excellent fit. The REF scale was invariant across sex and samples. The internal consistency of the complete scale was excellent and acceptable across the five first-order factors. Strong relationships were found with the positive dimension of the community assessment of psychic experience-42, as well as with aberrant salience. Low and moderate relationships were found with public self-consciousness, anxiety, and depression. Youths and patients diagnosed with schizophrenia and other psychotic disorders had a high mean IRs frequency. Male sex, greater age (among the adults), and the "causal explanations", "Songs, newspapers, books" and laughing and commenting" REF subscales showed predictive power in the diagnostic categories of schizophrenia and other psychotic disorders

One-way radiative transfer

We introduce the one-way radiative transfer equation (RTE) for modeling the transmission of a light beam incident normally on a slab composed of a uniform forward-peaked scattering medium. Unlike the RTE, which is formulated as a boundary value problem, the one-way RTE is formulated as an initial value problem. Consequently, the one-way RTE is much easier to solve. We discuss the relation of the one-way RTE to the Fokker–Planck, small-angle, and Fermi pencil beam approximations. Then, we validate the one-way RTE through systematic comparisons with RTE simulations for both the Henyey–Greenstein and screened Rutherford scattering phase functions over a broad range of albedo, anisotropy factor, optical thickness, and refractive index values. We find that the one-way RTE gives very good approximations for a broad range of optical property values for thin to moderately thick media that have moderately to sharply forward-peaked scattering. Specifically, we show that the error made by the one-way RTE decreases monotonically as the anisotropic factor increases and as the albedo increases. On the other hand, the error increases monotonically as the optical thickness increases and the refractive index mismatch at the boundary increases.Publicad