Estimation of aircraft aerodynamic derivatives using Extended Kalman Filter

Design of flight control laws, verification of performance predictions, and the implementation of flight simulations are tasks that require a mathematical model of the aircraft dynamics. The dynamical models are characterized by coefficients (aerodynamic derivatives) whose values must be determined from flight tests. This work outlines the use of the Extended Kalman Filter (EKF) in obtaining the aerodynamic derivatives of an aircraft. The EKF shows several advantages over the more traditional least-square method (LS). Among these the most important are: there are no restrictions on linearity or in the form which the parameters appears in the mathematical model describing the system, and it is not required that these parameters be time invariant. The EKF uses the statistical properties of the process and the observation noise, to produce estimates based on the mean square error of the estimates themselves. Differently, the LS minimizes a cost function based on the plant output behavior. Results for the estimation of some longitudinal aerodynamic derivatives from simulated data are presented.

Global instability of currencies: reasons and perspectives according to the state-corporation hegemonic stability theory

This paper analyses reasons of the instability of the world monetary system. The author considers this problem from historical and contemporary perspectives. According to presented point of view banknotes and electronic money which replaced gold and silver coins in popular circulation are the most important reason of the instability. There are also proven positive and negative consequences of money instability. Reforms of the world monetary system need agreement within the global collective hegemony of state-powers and transnational corporations.

SOCIAL BUSINESS DILEMMAS IN BRAZIL: REDE ASTACASE

ABSTRACTSocial businesses seek financial, social and even environmental results. Academic knowledge on how such organizations operate, however, has emerged more recently. This article sought to investigate qualitatively the main tensions and dilemmas occurring throughout the history of Rede Asta, a pioneer social business in direct catalog sales of artisanal products in Brazil. Results indicate the Rede Asta managers have experienced tensions and dilemmas in three of the four categories identified by Smith, Gonin, and Besharov (2013): social and financial performance, organizational aspects and learning. One of the dilemmas involves organizational aspects and learning, since Asta achieves feasibility with two organizations: a nonprofit association and a for-profit corporation. On perceptions of belonging, stakeholders declared they felt they were a part of the organization’s social and environmental goals; some even as activists.