Transition temperature dependence in perovskite ceramics as a function of grain size

Simple effective field arguments assuming an non isotropic layer of thickness L, covering the ferroelectric bulk grain of perovskite ceramics are used to determine an expression for the transition temperature TJL) as a function of grain linear size L. The surface to volume ratio increases as L decreases reducing the value of TJL). Experimental data for BaTiO₃ ceramics as a function of grain size are described reasonably well by the expression of T_c(L) obtained this way.     

Oscillation Test Strategy: A Case Study

In this paper is proposed as a case study the test of a folded cascode operational amplifier using the Oscillation Test Strategy (OTS). This Operational Amplifier (OPA) is chosen in order to evaluate the ability of OTS to test a more complex amplifier than those previously reported. To obtain comparative results, three different types of single-OPA oscillators are employed.A catastrophic-fault injection procedure is carried out using SPICE. In all oscillators, simulation results show that the fault coverage obtained is lower than those previously obtained by many researchers for simpler amplifiers. This fact suggests that OTS might be inconvenient for applications using the OPA targeted in this work and requiring high fault coverage.     

MITOM: a new unfolding code based on a spectra model method applied to neutron spectrometry

The MITOM code was developed at UAB (Universitat Autònoma de Barcelona) for unfolding neutron spectrometric measurements with a Bonner spheres system (BSS). One of the main characteristics of this code is that an initial parameterisation of the neutron energy components (thermal, intermediate and fast) is needed. This code uses the Monte Carlo method and the Bayesian theorem to obtain a set of solutions achieving different criteria and conditions between calculated and measured count rates. The final solution is an average of the acceptable solutions. The MITOM code was tested for ISO sources and a good agreement was observed between the reference values and the unfolded ones for global magnitudes. The code was applied recently to characterise both thermal SIGMA and CANEL/T400 sources of the IRSN facilities. The results of these applications were very satisfactory as well.     

A priori vs. a posteriori normalisation of citation indicators. The case of journal ranking

Two paradigmatic approaches to the normalisation of citation-impact measures are discussed. The results of the mathematical manipulation of standard indicators such as citation means, notably journal Impact Factors, (called a posteriori normalisation) are compared with citation measures obtained from fractional citation counting (called a priori normalisation). The distributions of two subfields of the life sciences and mathematics are chosen for the analysis. It is shown that both methods provide indicators that are useful tools for the comparative assessment of journal citation impact.     

On the applicability of Washburn law: study of mercury and water flow properties in cement-based materials

Materials and Structures - This paper deals with flow properties of mercury (Mercury Intrusion Porosimetry, MIP) and water (permeability measurements and capillarity) in building materials. The aim...     

Identification of the spinel (Cr,Al)3S4 in the internal sulfidation zone of Al-diffusion coatings

The thiospinel (Cr, Al)₃S₄ has been identified in the internal sulfidation zone of Al-diffusion coatings by electron diffraction in a transmission electron microscope. The Al/Cr ratio of this phase can vary over a rather broad range, obviously dependent on the Al/Cr ratio in the surrounding metallic matrix. The spinel can dissolve significant amounts of Ni and Mo, some Co but only traces of Ti. Increasing Al-content extents its stability to higher temperatures.     

City logistics in Spain: Why it might never work

Urban freight deliveries depend strongly on local regulations and policies to guarantee a tidy and efficient flow of goods towards commercial premises. However, the urban freight delivery system in Spain, which is even more complicated due to the urban morphology and driving behavior, also suffers from a combination of negative factors, including uneven regulations, lack of enforcement and obsolete policies. We present the picture of the current scenario and the typical regulation schemes, analyzing the reasons for failure of the system and the possible efforts, relatively cheap and easy to implement, that could be undertaken towards improvement.     

Spatiotemporal methods for analysis of urban system dynamics: an application to Chile

This paper presents a methodological procedure to evaluate the influence of spatial proximity on evolution of cities to detect regional differences in their spatiotemporal dynamics. The six-step method based on a set of statistical methods can be computed with a new R package: estdaR. The first step consists of the usual characterization of the cross-sectional distribution of the urban areas by means of nonparametric estimations of density functions for a set of significant years. In the second and third steps, the growth process is modeled as a first-order stationary Markov chain to evaluate the effect of global and local spatial autocorrelation on the transition probabilities with a set of indices based on the spatial version of the standard Markov chain. The fourth, fifth, and sixth steps perform in-depth analysis to detect the existence and interaction of spatial regimes in the movement direction and ranking mobility of urban distribution. We apply this novel strategy for the period 1930–2002 to analyze the entire Chilean urban system—not only the Central Zone, in which most of the population and economic activities are concentrated, but also other urban zones in the country.     

Biodegradation of oxadiazon by a soil isolated Pseudomonas fluorescens strain CG5: Implementation in an herbicide removal reactor and modelling

An oxadiazon-degrading bacterial, Pseudomonas strain CG5, was isolated from an agricultural contaminated soil. This strain CG5 was able to grow on 10mg of oxadiazon per l, yielding 5.18+/-0.2 mg of protein biomass mol(-1). GC-MS analyses of the metabolites from oxadiazon catabolism revealed its dehalogenation and degradation to form non-toxic end-products, cells were then immobilized by adsorption on a ceramic support to be used as biocatalysts in herbicide removal biofilm-reactor processes. Seventy-two per cent of the oxadiazon was removed, and the maximum specific substrate uptake rate was 10.63+/-0.5 microg h(-1) mg(-1) prot. A new mathematical model was developed to interpret and predict the behaviour of the bacteria and pollutants in a biofilm-reactor system, to consider biofilm structural and morphological properties.     

Influence of ozone-limonene reactions on perceived air quality

This study conducted short-term assessments of perceived air quality (PAQ) for six different realistic concentrations of ozone and limonene, separately or together, in room air. The impact of filtration and the influence of the ozone generation method were also examined. The evaluations were made in four identical 40 m3 low-polluting test offices ventilated at 1.4 h(-1) or in two identical 30 m3 stainless-steel chambers ventilated at 1.9 h(-1). Concentrations of ozone, total volatile organic compounds and size-fractionated particles were continuously monitored in each experiment. The results indicate that, for each of the six conditions, the PAQ was poorer when ozone and limonene were present together compared with when only ozone or only limonene was present. In the test offices a correlation was observed between the number of secondary organic aerosols produced by a given ozone/limonene condition and the sensory pollution load for that condition. The particles themselves do not appear to be the primary causative agents, but instead are co-varying surrogates for sensory offending gas-phase species. PRACTICAL IMPLICATIONS: Although the health consequences of long-term exposures to the products of ozone-initiated indoor chemistry remain to be determined, we judge that the sensory offending nature of selected products provides an additional reason to limit indoor ozone levels. Devices that emit ozone at significant rates should not be used indoors. Ozone-filtration of make-up air should also be beneficial in mechanically ventilated buildings located in regions that repeatedly violate outdoor ozone standards. Additionally, the use of limonene containing products should be curtailed during periods when indoor ozone levels are elevated.