Mirror formation control in the vicinity of an asteroid

Two strategies are presented for the positioning and control of a spacecraft formation designed to focus sunlight onto a point on the surface of asteroid, thereby sublimating the material and ejecting debris creating thrust. In the first approach, the formation is located at artficial equilibrium points around the asteroid and controlled using the force from the solar radiation pressure. The second approach determines the optimal periodic formation orbits, subject to the gravitational perturbations from the asteroid, the solar radiation pressure and the control acceleration derived from a control law

Attitude and Phase Synchronization of Formation Flying Spacecraft: Lagrangian Approach

This article presents a unified synchronization framework with application to precision formation flying spacecraft. Central to the proposed innovation, in applying synchroniza- tion to both translational and rotational dynamics in the Lagrangian form, is the use of the distributed stability and performance analysis tool, called contraction analysis that yields exact nonlinear stability proofs. The proposed decentralized tracking control law synchronizes the attitude of an arbitrary number of spacecraft into a common time-varying trajectory with global exponential convergence. Moreover, a decentralized translational tracking control law based on phase synchronization is presented, thus enabling coupled translational and rotational maneuvers. While the translational dynamics can be adequately controlled by linear control laws, the proposed method permits highly nonlinear systems with nonlinearly coupled inertia matrices such as the attitude dynamics of space-craft whose large and rapid slew maneuvers justify the nonlinear control approach. The proposed method integrates both the trajectory tracking and synchronization problems in a single control framework

Tiling of the five-fold surface of Al(70)Pd(21)Mn(9)

The nature of the five-fold surface of Al(70)Pd(21)Mn(9) has been investigated using scanning tunneling microscopy. From high resolution images of the terraces, a tiling of the surface has been constructed using pentagonal prototiles. This tiling matches the bulk model of Boudard et. al. (J. Phys.: Cond. Matter 4, 10149, (1992)), which allows us to elucidate the atomic nature of the surface. Furthermore, it is consistent with a Penrose tiling T^*((P1)r) obtained from the geometric model based on the three-dimensional tiling T^*(2F). The results provide direct confirmation that the five-fold surface of i-Al-Pd-Mn is a termination of the bulk structure.Comment: 4 pages, 4 figure

A Default Logic Patch for Default Logic

International audienceThis paper is about the fusion of multiple information sources represented using default logic. More precisely, the focus is on solving the problem that occurs when the standard-logic knowledge parts of the sources are contradictory, as default theories trivialize in this case. To overcome this problem, it is shown that replacing each formula belonging to Minimally Unsatisfiable Subformulas by a corresponding supernormal default allows appealing features. Moreover, it is investigated how these additional defaults interact with the initial defaults of the theory. Interestingly, this approach allows us to handle the problem of default theories containing inconsistent standard-logic knowledge, using the default logic framework itself

Strategic responses to global challenges: The case of European banking, 1973–2000

In applying a strategy, structure, ownership and performance (SSOP) framework to three major clearing banks (ABN AMRO, UBS, Barclays), this article debates whether the conclusions generated by Whittington and Mayer about European manufacturing industry can be applied to the financial services sector. While European integration plays a key role in determining strategy, it is clear that global factors were far more important in determining management actions, leading to significant differences in structural adaptation. The article also debates whether this has led to improved performance, given the problems experienced with both geographical dispersion and diversification, bringing into question the quality of decision-making over the long term

Misdevelopments, Pathologies, and Normative Revolutions: Normative Reconstruction as Method of Critical Theory

In this article I argue that the method of normative reconstruction underlying Freedom's Right undermines Critical Theory's aspiration to be a force that is unreservedly critical and progressive. I start out by giving a brief account of the four premises of the method of normative reconstruction and unpack their implications for how Honneth conceptualizes social pathologies and misdevelopments, specifically that these notions are no longer linked to radical critique and normative revolution. In the second part, I demonstrate that abandoning forms of radical critique and normative revolution is internally linked to adopting this method, before arguing that Freedom's Right contains no resources to account for why abandoning them does not amount to a deficiency. In the final part, I point out two problematic implications of turning away from radical critique and normative revolution for the very project Honneth pursues in Freedom's Right. I show that Honneth's own view about the limited scope of application of the method of normative reconstruction and his account of the dangers associated with social misdevelopments give us (additional) reasons to consider this method to be incomplete. Finally, I contend that the explanatory power of Freedom's Right is dubious because methodological premises that form part of normative reconstruction lead Honneth to ignore relevant alternative explanations of processes of deviation and disassociation from norms of social freedom, which he characterizes as social misdevelopments

Kognitiv-psychoedukative Gruppenintervention bei stationären Patienten mit depressiven Erkrankungen – Ergebnisse einer prospektiven Pilotstudie

Background: Psychoeducational interventions that provide disorder-related information in a goal-oriented and structured manner have been integrated in psychiatric and psychotherapeutic approaches. The present cognitive psychoeducational group programme for inpatients with affective disorders is based on a multidimensional functional illness concept which covers aspects of vulnerability, stressors and coping strategies. It covers information about the disorder and its treatment options, building up rewarding activities, cognitive restructuring and relapse prevention. Materials und Methods: This programme was developed and modified at the University of Munich, Department of Psychiatry (LMU). A feasibility study was set up in a follow-up single group design and analyses of variance (ANOVAs) were performed. A total of 231 patients participated in 46 groups. Results: 125 patients evaluated the effectiveness of the programme and its treatment strategies. The group programme was widely accepted among patients that were pharmacologically and psychotherapeutically treated: more than three quarters of the patients rated its contents to be informative, helpful and applicable to everyday living. Conclusions: Inpatients with affective disorders may already benefit from a structured group programme if it takes into account their cognitive and motivational deficits. The group leaders' didactic and psychotherapeutic strategies as well as the patients' exchanging ideas with each other play a central role. In the course of further investigations the programme was differentiated for patients with major depression or bipolar disorders

Dynamics of heteropolymers in dilute solution: effective equation of motion and relaxation spectrum

The dynamics of a heteropolymer chain in solution is studied in the limit of long chain length. Using functional integral representation we derive an effective equation of motion, in which the heterogeneity of the chain manifests itself as a time-dependent excluded volume effect. At the mean field level, the heteropolymer chain is therefore dynamically equivalent to a homopolymer chain with both time-independent and time-dependent excluded volume effects. The perturbed relaxation spectrum is also calculated. We find that heterogeneity also renormalizes the relaxation spectrum. However, we find, to the lowest order in heterogeneity, that the relaxation spectrum does not exhibit any dynamic freezing, at the point when static (equilibrium) ``freezing'' transition occurs in heteropolymer. Namely, the breaking of fluctuation-dissipation theorem (FDT) proposed for spin glass dynamics does not have dynamic effect in heteropolymer, as far as relaxation spectrum is concerned. The implication of this result is discussed