Robust scheduled control of longitudinal flight with handling quality satisfaction

Classic flight control systems are still widely used in the industry because of acquired experience and good understanding of their structure. Nevertheless, with more stringent constraints, it becomes difficult to easily fulfil all the criteria with these classic control laws. On the other hand, modern methods can handle many constraints but fail to produce low order controllers. The following methodology proposed in this paper addresses both classic and modern flight control issues, to offer a solution that leverages the strengths of both approaches. First, an H∞ synthesis is performed in order to get controllers which satisfy handling qualities and are robust withrespect to mass and centre of gravity variations. These controllers are then reduced and structured by using robust modal control techniques. In conclusion, a self-scheduling technique is described that will schedule these controllers over the entire flight envelope

Many parameter Hoelder perturbation of unbounded operators

If $u\mapsto A(u)$ is a $C^{0,\alpha}$-mapping, for $0< \alpha \le 1$, having as values unbounded self-adjoint operators with compact resolvents and common domain of definition, parametrized by $u$ in an (even infinite dimensional) space, then any continuous (in $u$) arrangement of the eigenvalues of $A(u)$ is indeed $C^{0,\alpha}$ in $u$.Comment: LaTeX, 4 pages; The result is generalized from Lipschitz to Hoelder. Title change

First-principles study of the ferroelectric Aurivillius phase Bi2WO6

In order to better understand the reconstructive ferroelectric-paraelectric transition of Bi2WO6, which is unusual within the Aurivillius family of compounds, we performed first principles calculations of the dielectric and dynamical properties on two possible high-temperature paraelectic structures: the monoclinic phase of A2/m symmetry observed experimentally and the tetragonal phase of I4/mmm symmetry, common to most Aurivillius phase components. Both paraelectric structures exhibits various unstable modes, which after their condensation bring the system toward more stable structures of lower symmetry. The calculations confirms that, starting from the paraelectric A2/m phase at high temperature, the system must undergo a reconstructive transition to reach the P2_1ab ferroelectric ground state.Comment: added Appendix and two table

Some shocking aspects of EMU enlargement

This paper uses a structural vector autoregression to examine differences in demand and supply shocks and the response to these shocks between EMU member countries and three other groups of countries. The first group includes non-EMU EU countries, the second group EFTA countries and the third group central and eastern European countries which seek EU membership over the next years. Our results suggest that, so far, EMU enlargement towards central and eastern European countries would involve significantly higher costs than EMU enlargement towards countries of the other two groups. --European Monetary Integration,International Monetary Arrangements and Institutions

Unemployment and employment dynamics in the Mexican segmented labour market

This paper analyses unemployment and employment dynamics in the urban Mexican labour market. We use amethod to distinguish between the effects of duration dependence and unobserved heterogeneity. Cohort effects are added and identified within the dependent concurrent risks model. We consider the exit from unemployment to the formal and informal sector; the transitions between sectors; and the transitions from the two types of employment to unemployment. The model is estimated on quarterly urban Mexican aggregated data over the period 1987-2001 stratified by sex, age, and education level. It turns out that for all groups of unemployed there is nonmonotonous duration dependence. Unobserved heterogeneity is not found in all groups of unemployed individuals. The first results, obtained from the analysis of the unemployment dynamics do not enable us to conclude that both formal and informal sectors play a specific role, but neither do they show a dynamic or specific behaviour; with similar cohort effects and different duration dependences, the sectors appear symmetrical. The transitions between sectors show shapes of dependence, where we find a primacy of the formal sector over the informal one for some categories of workers, especially males and the more educated. An asymmetrical mechanism within the formal sector thus seems to take place with the employment length in this sector, keeping those workers within the same type of employment. Between the two following quarters, the probabilities of returning to unemployment differ greatly according to the categories of workers and the origin sectors. It is difficult to draw conclusions from those mechanisms of nonmonotonous dependence in the analysis of transitions from employment to unemployment. The transition risks from formal employment, that is to saymobility between sectors or a return to unemployment are overall homogeneous within the different categories of workers. The exit rates from informal employment are very different. Regarding the mobility between sectors from informal to formal, the presence of heterogeneity is systematically significant (except for the less educated workers). Rather than pure cyclical effects, it seems nevertheless that cohort effects make account of the labour market mutations and of the transformations and particularly of the role of employment sectors

Bounding the homological finiteness length

We give a criterion for bounding the homological finiteness length of certain HF-groups. This is used in two distinct contexts. Firstly, the homological finiteness length of a non-uniform lattice on a locally finite n-dimensional contractible CW-complex is less than n. In dimension two it solves a conjecture of Farb, Hruska and Thomas. As another corollary, we obtain an upper bound for the homological finiteness length of arithmetic groups over function fields. This gives an easier proof of a result of Bux and Wortman that solved a long-standing conjecture. Secondly, the criterion is applied to integer polynomial points of simple groups over number fields, obtaining bounds established in earlier works of Bux, Mohammadi and Wortman, as well as new bounds. Moreover, this verifes a conjecture of Mohammadi and Wortman.Comment: Revised versio