Dry Friction Discontinuous Computational Algorithms

The design of high position accuracy servo mechanisms (such as an aircraft primary command EHA), involves the deep knowledge of their behaviour, markedly affected by the Coulomb friction. The proper evaluation of the friction forces and torques is usually necessary when an accurate simulation of the servomechanisms dynamic behaviour is requested in order to perform a suitable design of the system itself. To the purpose, the authors consider a servomechanism consisting of a hydraulic motor element (translational or rotary) coupled with an electro-hydraulic servovalve as a controller; the dynamic behaviour of these elements may be strongly dependent on the dry friction forces or torques acting on the moving parts, particularly of the motor element

Redundant hydraulic secondary flight control systems behavior in failure conditions

The flight control systems, designed in order to assure the necessary safety level even in failure conditions, are generally characterized by a proper redundant layout. The redundancies must be designed in order to assure an adequate system behavior when some failures are present; in fact an incorrect layout may cause serious shortcomings concerning the response when some component is not operational. Therefore the usual correct design activities request the complete analysis of the system behavior in failure condition. The work analyses the response of a redundant secondary flight control hydraulic servo-mechanism equipped with some proper equalization devices, when some of the most probable and representative failures are present. It must be noted that the redundancy layout, designed in order to assure the necessary safety level even in failure conditions, may behave improperly during normal operations, if the system architecture is unsuitable, when manufacturing defects are present. The improper behavior, generally consisting of force fighting or speed fighting caused by different offsets or asymmetries between the two sections of the system, may be usually overcome by means of a suitable equalization device. Therefore, the system behavior during and following the failure transient greatly depends on both its redundancy architecture and related equalization device. The above mentioned problems have been studied by means of an appropriate physical-mathematical model of a typical electro-hydraulic servo-mechanism prepared to the purpose, performing a certain number of simulations of representative actuations in which different types of failures are accurately modeled. In the opinion of the authors, this paper concerns a topic quite neglected but important in the technical literature. At the best of the authors’ knowledge, no specific scientific work in this field is available, excepting some industrial technical reports

Use of microbial fuel cells for soil remediation. A preliminary study on DDE

DDE (2,2-bis (p-chlorophenyl)-1,1-dichloroetylene) is a very persistent and bioaccumulative pesticide and its residues are continuously found in the environment. Among the green remediation strategies for soil recovery, terrestrial Microbial Fuel Cells (MFC) are arousing great interest in scientific community. MFCs transform energy stored in the chemical bonds of organic compounds into electrical energy thanks to exo-electrogen microorganisms naturally occurring in soil, which catalyse oxidation and reduction reactions in the area between two graphite electrodes. This work reports preliminary data on the use of MFCs for promoting soil decontamination from DDE. Several experimental conditions (e.g. addition of compost and open/closed circuit) were applied for assessing how to improve MFC performance in favouring DDE removal. MFCs promoted a significant DDE removal (39%) after 2 months, while at the same time any pesticide decrease was observed in the batch condition. Compost addition stimulated microbial activity and improved MFC performance for a longer time

Complexity of Generic Limit Sets of Cellular Automata

The generic limit set of a topological dynamical system of the smallest closed subset of the phase space that has a comeager realm of attraction. It intuitively captures the asymptotic dynamics of almost all initial conditions. It was defined by Milnor and studied in the context of cellular automata, whose generic limit sets are subshifts, by Djenaoui and Guillon. In this article we study the structural and computational restrictions that apply to generic limit sets of cellular automata. As our main result, we show that the language of a generic limit set can be at most $\Sigma^0_3$-hard, and lower in various special cases. We also prove a structural restriction on generic limit sets with a global period.Comment: 13 pages, 2 figure

Investigation of α-cluster states in 13C via the (6Li,d) reaction

The 9Be(6Li,d)13C reaction was used to investigate possible α-cluster states in 13C. The reaction was measured at 25.5 MeV incident energy, employing the São Paulo Pelletron-Enge-Spectrograph facility and the nuclear emulsion detection technique. Ten out of sixteen known levels of 13C, up to 11 MeV of excitation, were observed and, due to the much improved energy resolution of 50 keV, at least three doublets could be resolved. This work presents a preliminary analysis of five of the most intensely populated states, also in comparison with the results of former transfer studies

Risk Factors for Fecal and Urinary Incontinence After Childbirth: The Childbirth and Pelvic Symptoms Study

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73402/1/j.1572-0241.2007.01364.x.pd

Changes in Physical Activity after Sacrocolpopexy for Advanced Pelvic Organ Prolapse

To describe changes in physical activity one year after sacrocolpopexy for pelvic organ prolapse