Robustness analysis of discrete predictor-based controllers for input-delay systems

In this article, robustness to model uncertainties are analysed in the context of discrete predictor-based state-feedback controllers for discrete-time input-delay systems with time-varying delay, in an LMI framework. The goal is comparing robustness of predictor-based strategies with respect to other (sub)optimal state feedback ones. A numerical example illustrates that improvements in tolerance to modelling errors can be achieved by using the predictor framework.     

Groebner Bases and Distance of Cyclic Codes

 Recently some methods have been proposed to find the distance of cyclic codes using Gr?bner bases. We present a similar method, whose computational cost is significantly lower. Received: April 24, 2001; revised version: February 14, 2002     

Polymeric fluorine-free electrolyte for application in DMFC

We present latest results on the development of a new solid electrolyte for DMFC application. Films are obtained through fluorine-free chemistry consisting of grafting reaction between polyethylene film, preliminary irradiated, and styrene monomers. This reaction proceeds through the formation of hydroperoxide groups activated by ferrous catalyst that initiates the polymerization reaction with styrene. Sulfonic groups are then introduced on the aromatic rings by sulfonation with chlorosulfonic acid. Functional properties of membranes are then characterized out of cell through ion conductivity and methanol permeability measurements. Obtained results are very promising for application in DMFC.     

Development of “kink” in the output I–V characteristics of pseudomorphic hemt's after hot-electron accelerated testing

Large decreases in the drain current in the linear and low V_ds region followed by a “kink” in the output I_d-V_ds characteristics have been found after hot electron stress test in AlGaAs/InGaAs/GaAs power pseudomorphic HEMT's. Decrease in the transconductance measured in linear region, increase in the drain parasitic resistance and trasconductance frequency dispersion have also been observed and attributed to the generation of electron traps in the gate-to-drain access region.     

Spectral study and classification of worldwide locations considering several multijunction solar cell technologies

Multi‐junction solar cells are widely used in high‐concentration photovoltaic systems (HCPV) attaining the highest efficiencies in photovoltaic energy generation. This technology is more dependent on the spectral variations of the impinging Direct Normal Irradiance (DNI) than conventional photovoltaics based on silicon solar cells and consequently demands a deeper knowledge of the solar resource characteristics. This article explores the capabilities of spectral indexes, namely, spectral matching ratios (SMR), to spectrally characterize the annual irradiation reaching a particular location on the Earth and to provide the necessary information for the spectral optimization of a MJ solar cell in that location as a starting point for CPV module spectral tuning. Additionally, the relationship between such indexes and the atmosphere parameters, such as the aerosol optical depth (AOD), precipitable water (PW), and air mass (AM), is discussed using radiative transfer models such as SMARTS to generate the spectrally resolved DNI. The network of ground‐based sun and sky‐scanning radiometers AErosol RObotic NETwork (AERONET) is exploited to obtain the atmosphere parameters for a selected bunch of 34 sites worldwide. Finally, the SMR indexes are obtained for every location, and a comparative analysis is carried out for four architectures of triple junction solar cells, covering both lattice match and metamorphic technologies. The differences found among cell technologies are much less significant than among locations. Copyright © 2016 John Wiley & Sons, Ltd.     

Dynamic estimations of metabolic fluxes with constraint-based models and possibility theory

Living cells can be modelled by successively imposing known constraints that limit their behaviour, such as mass balances, thermodynamic laws or enzyme capacities. The resulting constraint-based models enclose all the functional states that the modelled cells may exhibit. Then, predictions can be obtained from the models in two main ways: adding experimental data to determine the state of cells at given conditions (MFA) or invoking an assumption of evolved optimal behaviour (FBA). Both MFA and FBA predictions are typically performed at steady state. However, it is easy to take extracellular dynamics into account. This work explores the benefits of using possibility theory to get these dynamic predictions. It will be shown that the possibilistic methods (a) provide rich estimates for time-varying fluxes and metabolite concentrations, (b) account for uncertainty and data scarcity, and (c) give predictions relaxing the optimality assumption of FBA. On the other hand, these methods could serve as basis for monitoring and fault detection systems in industrial bioprocesses.     

Composite chiral structures for morphing airfoils: Numerical analyses and development of a manufacturing process

This paper investigates complex composite cellular structures featuring a chiral topology with the ability to undergo large overall displacements with limited straining of its components. Numerical analyses are performed to exploit such properties in the design of a morphing airfoil. The advantages associated with the use of composites are investigated by comparing the numerical results with those obtained with a metallic structure. A manufacturing process is then developed to assemble the considered structural configurations using composite materials. The novel process developed is described as applied to the manufacturing of macro chiral components that are tested to evaluate their ability to undergo large deformations. Finally, detailed numerical models of the manufactured structures are presented as a possible approach to evaluate the strength of the proposed configuration.     

Swallowing changes in cerebrovascular accidents: incidence, natural history, and repercussions on the nutritional status, morbidity, and mortality

OBJECTIVE: To determine the frequency of dysphagia in CVA, its natural history and value as a risk factor of respiratory infection, malnutrition and death. PATIENTS AND METHODS: A prospective study was made of 187 consecutive patients with cerebrovascular accidents (CVA). A standardized test for dysphagia was done during the first two days of the illness and repeated three days a week. The levels of urea, total proteins and albumin were determined on admission and on discharge. The patients were questioned by phone after 6 months. RESULTS: There was dysphagia of liquids in 36.4% of the patients. The incidence of dysphagia for semisolids was of the same frequency but more severe. Coma was the cause of inability to swallow in 25.7% of the patients. During their stay in hospital one third of the patients with dysphagia died, one third became normal and one third still had dysphagia when they were discharged. After one week, one, three and six months respectively, the cure rate for dysphagia was 29.4%, 4.1%, 55.9% and 55.9%, and survival 83.8%, 67.6%, 61.8% and 60.3%. Thus after 6 months only 3 patients (4.4%) were alive and dysphagic. Half of the 'cures' occurred in the first week, and none occurred after more than 77 days. As compared to the non-dysphagic patients, the dysphagic patients had 10 times more risk of respiratory infection, 18 times higher risk of death, greater loss of albumin and less loss of urea. CONCLUSIONS: There is a high prevalence of dysphagia in CVA and although functional prognosis is not unfavorable, respiratory infections, malnutrition and death are frequent.