Scaling properties of wood fractured surfaces are obtained from samples of three different sizes. Two different woods are studied: Norway spruce and Maritime pine. Fracture surfaces are shown to display an anomalous dynamic scaling of the crack roughness. This anomalous scaling behavior involves the existence of two different and independent roughness exponents. We determine the local roughness exponents ${\zeta}_{loc}$ to be 0.87 for spruce and 0.88 for pine. These results are consistent with the conjecture of a universal local roughness exponent. The global roughness exponent is different for both woods, $\zeta$ = 1.60 for spruce and $\zeta$ = 1.35 for pine. We argue that the global roughness exponent $\zeta$ is a good index for material characterization.Comment: 7 two columns pages plus 8 ps figures, uses psfig. To appear in Physical Review

The production of iron metal with low greenhouse gas emissions can be performed by electrolysis. However, the electrolytic reduction of iron ore is not a technique that has reached a high degree of knowledge and development. With the aim of getting insight into the electrochemical reaction mechanism, this work shows that the reduction of iron ore to metal at low temperature in alkaline electrolyte is possible and occurs in a solid-state macroscopic mode. Electrochemical reactions take place in the volume of the solid, progressing from its outer surface toward the core, leading to full conversion to metal. A magnetite intermediate phase has been identified and high current efficiency is measured. Such a reaction occurs at high reaction rates, which further stimulates the interest of producing iron metal by the sole use of electricity.

The electrodeposition of metal iron from iron dissolved species in alkaline media has been investigated. Dissolved ferric species in equilibrium with hematite (α-Fe2normalO3) have been electrochemically identified and their reduction to iron was demonstrated. The reduction efficiency was poor, however, because of the low concentration of dissolved matter (2.6×10−3M) . In order to determine more precisely the electrochemical features of the deposition reaction from iron ions, more concentrated solutions at 1.9×10−2M have been obtained using an iron anode as the ion source. Voltammetric and chronoamperometric investigations using a rotating disk electrode revealed that such concentrated solutions contain ferric and ferrous species, with higher concentration of the trivalent form. Metal can be deposited with higher current efficiency in these concentrated solutions with less than 30% of the current spent in hydrogen evolution.

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From load-unloading cycles applied on wood notched specimens subjected to three-point bending, we show that the concept of 'equivalent LEFM', usually used for the quasibrittle materials, can be successfully applied to the fracture behavior of wood in mode I. Within this equivalent linear elastic framework, the quasibrittle fracture behavior of wood leads to an R-curve which is evaluated and discussed. On the other hand, the estimate of the peak load (or maximum load) of a structure as a function of the corresponding R-curve is an important problem for a building material such as wood. After a review of some general results about the connection between the R-curve and the shape of the load-deflection curve, we propose a single equation, i.e., valid for a fracture test under load-control or displacement-control, allowing to estimate the crack length corresponding to every extremum of a load-deflection curve.