An Inverse Dynamics Approach to Control Lyapunov Functions

With the goal of moving towards implementation of increasingly dynamic behaviors on underactuated systems, this paper presents an optimization-based approach for solving full-body dynamics based controllers on underactuated bipedal robots. The primary focus of this paper is on the development of an alternative approach to the implementation of controllers utilizing control Lyapunov function based quadratic programs. This approach utilizes many of the desirable aspects from successful inverse dynamics based controllers in the literature, while also incorporating a variant of control Lyapunov functions that renders better convergence in the context of tracking outputs. The principal benefits of this formulation include a greater ability to add costs which regulate the resulting behavior of the robot. In addition, the model error-prone inertia matrix is used only once, in a non-inverted form. The result is a successful demonstration of the controller for walking in simulation, and applied on hardware in real-time for dynamic crouching

The Main Determinants of Insurance Purchase: An Empirical Study on Crop Insurance Policies in France

Using data for 2002-2005 on a representative survey of French farms (FADN-RICA), we investigate the different factors that lead farmers to insure against crop risk. Our analysis takes into account a mix of both standard individual, financial and agricultural criteria. Cross-sectional and longitudinal analyses as well as logistic regressions underline the main differences between insured and non-insured farms. Compared to non-insured farms, we find that insured farms present greater financial and agricultural sizes, a more diversified production and have been motivated by the occurrence of recent catastrophic climatic events. Although essential in the cross-sectional analysis, the influence of financial parameters in the decision to insure is mitigated. On the other hand, the agricultural characteristics of the farms confirm their leading influence for the subscription of crop insurance policies.Insurance, Demand, Crop insurance, Catastrophe risk, Risk and Uncertainty,

The main determinants of insurance purchase. An empirical study on crop insurance policies in France

Using data for 2002-2005 on a representative survey of French farms (FADN-RICA), we investigate the different factors that lead farmers to insure against crop risk. Our analysis takes into account a mix of both standard individual, financial and agricultural criteria. Cross-sectional and longitudinal analyses as well as logistic regressions underline the main differences between insured and non-insured farms. Compared to non-insured farms, we find that insured farms present greater financial and agricultural sizes, a more diversified production and have been motivated by the occurrence of recent catastrophic climatic events. Although essential in the cross-sectional analysis, the influence of financial parameters in the decision to insure is mitigated. On the other hand, the agricultural characteristics of the farms confirm their leading influence for the subscription of crop insurance policies.

Simulation of Laser Propagation in a Plasma with a Frequency Wave Equation

The aim of this work is to perform numerical simulations of the propagation of a laser in a plasma. At each time step, one has to solve a Helmholtz equation in a domain which consists in some hundreds of millions of cells. To solve this huge linear system, one uses a iterative Krylov method with a preconditioning by a separable matrix. The corresponding linear system is solved with a block cyclic reduction method. Some enlightments on the parallel implementation are also given. Lastly, numerical results are presented including some features concerning the scalability of the numerical method on a parallel architecture

Sous-investissement et suppression d’effectifs : vers une réduction des coûts d’agence

Cet article montre que la possibilité pour une firme endettée de réduire ses effectifs permet de supprimer les situations de sous-investissement et les coûts d’agence qui leurs sont liés. L’influence de la possibilité de réduire les effectifs sur la richesse des parties prenantes de l’entreprise est étudiée. Seuls les créanciers et les travailleurs profitent de la politique de réduction d’effectifs. La valeur des actions demeure inchangée. Enfin, dans le modèle, une structure du capital optimale existe et la valeur de l’entreprise endettée apparaît supérieure à celle de l’entreprise sans dette.This paper argues that the agency costs of under-investment could be eliminated when the levered firm takes the possibility to reduce its employees. We focus on the effect of employees reductions on wealth of stakeholders in the unlevered and levered firms. Bondholders and employees only benefit from these operations. It is shown that an optimal capital structure exists and that the levered firm value is more than the unlevered firm value