The view from the top

The challenge of integrating large amounts of renewable energy resources into the electric sector requires updated transmission analysis techniques. Economic planning, primarily in the form of value-based planning over interconnectionwide areas, is needed before performing the traditional single-hour, capacity-based reliability analyses.     

Arrayed silicon avalanche cathodes

Silicon avalanche cathodes (SACs) consisting of a heavily doped shallow (less than 300 A) p-n junctions were fabricated, characterized, and used as electron sources in Si-based microvacuum diodes. The emission current was investigated as a function of diode reverse-biased voltage and external field. The field was provided by an anode placed approximately 1 mm above the cathode to simulate the field which would be obtained with a built-on-chip anode. Eighteen different shapes and sizes of SACs were tested. An emission current of 0.24 μA and an emission efficiency (emission current/total diode current) of 2.1×10^-5 were observed from the single bare Si p-n junction cold cathode     

Use of the polar method to predict the hygroscopic transient stresses for balanced [θ/−θ] nS laminates under asymmetrical environmental loadings

This paper presents an analytical method to assess the transient hygroscopic stresses in laminated composite plates due to asymmetrical constant environmental conditions. The developed method permits us to determine directly the values of such stresses without the calculation of the moisture concentration through laminated plates. The present method is the extension of the method developed by Tounsi and Adda-Bedia [Tounsi, A., Adda-Bedia, E.A.: Appl Compos Mater 10, 1–18 (2003)] which is limited only to the problems with symmetrical environmental conditions. Thus by the present method, we can study the effect of symmetrical and asymmetrical environmental conditions. A validation was made with the results of the same authors [Tounsi, A., Adda-Bedia, E.A.: Appl Compos Mater 10, 1–18 (2003); Sereir, Z., et al.: J. Thermal Stres. 28(9), 889–910 (2005)] for symmetrical environmental conditions and the results of benkeddad [Benkeddad, A., et al.: Compos. Struct. 30(2), 201–215 (1995)] for asymmetrical environmental conditions. In order to evaluate the performances of each balanced [θ/?θ] _S laminate proposed for this applications, we use the polar method introduced by Verchery [Vannucci, P., Verchery, G.: Int. J. Solids Struct. 38, 9281–9294 (2001), Vincenti, A., et al.: Composites: Part A, 1525–1532 (2001), Valot, E., et al.: Compos. Struct. 60, 413–429 (2003), Vannucci, P., Verchery, G.: Compos. Sci. Technol. 61, 1465–1473 (2001)]. This method enables us to locate the favourite directions of the mechanical characteristics and to estimate the degree of anisotropy of all stacking sequences. Therefore, we can reduce the transient hygroscopic stresses, particularly at the edges of laminated plates. Through this theoretical study presented here, we hope to contribute to the understanding of hygrothermal behaviour of composite laminated plates.     

Proprietes electriques et magnetiques des ferrites oxydes La1−xSrxFeO3−y

The study of electrical and magnetic properties of oxidized ferrites La_1?xSr_xFeO_3?y (0 ? x ?1) has shown that iron is likely in a low spin state. Moreover, it appears from the Seebeck coefficient vs composition measurements that the conduction occurs essentially over the octahedral sites, but that the oxygen vacancies trap partially electrons around iron (+III) in tetrahedral sites. A conduction model is proposed.     

A frequentist approach to estimating the force of infection for a respiratory disease using repeated measurement data from a birth cohort

This article aims to develop a probability-based model involving the use of direct likelihood formulation and generalised linear modelling (GLM) approaches useful in estimating important disease parameters from longitudinal or repeated measurement data. The current application is based on infection with respiratory syncytial virus. The force of infection and the recovery rate or per capita loss of infection are the parameters of interest. However, because of the limitation arising from the study design and subsequently, the data generated only the force of infection is estimable. The problem of dealing with time-varying disease parameters is also addressed in the article by fitting piecewise constant parameters over time via the GLM approach. The current model formulation is based on that published in White LJ, Buttery J, Cooper B, Nokes DJ and Medley GF. Rotavirus within day care centres in Oxfordshire, UK: characterization of partial immunity. Journal of Royal Society Interface 2008; 5: 1481-1490 with an application to rotavirus transmission and immunity.