SiC-Al2O3 ceramic foams with 30 to 75 pores per linear inch (ppi) were used to access the application of pore size obtained by image analysis to estimate the cellular materials permeability through Ergun's equation. Samples were sliced and the pore size distribution, cross-sectional porosity and pore density were evaluated as a function of the slice thickness based on optical and X-ray computerized tomography acquired images. The average pore sizes were used to calculate permeability constants (k1 and k2) of Ergun's equation, which were compared to those experimentally obtained under water flow. Results indicated that the optical diameter distribution was very sensitive to the number of pore layers. Deviation between experimental and calculated values depended on the slice thickness. Nevertheless, the introduction of pore size obtained by image analysis into Ergun's equations seems to give fair results to assess the permeability of ceramic foams

The Arya and Paris (AP) model predicts soil water retention curves from soil particle‐size distribution (PSD) data based on the similarity between these two functions. The AP model estimates pore radius (ri) from the radius (Ri) of spherical particles by scaling pore length with a parameter α. This paper evaluates the performance of the AP model with representative Brazilian soil types using three constant α values: α = 1.38, 0.938 (literature values), and 0.977, (obtained in the present work); and a α‐variable approach, where α is determined as a function of soil water content (θ). The study was performed with 104 soil samples collected in three sites. The soil PSD curves were obtained with an automatic soil particle analyzer based on the attenuation of γ‐ray by dispersed soil particles falling in a liquid medium and the soil water retention were measured with tension table and Richard chamber methods. The best mathematical representation of the α = f(θ) relationship was obtained with a first‐order exponential decay equation [α = 0.947 + 0.427exp(−θ/0.129)] that provided values of α in the range from 1.37 (θ = 0 m3 m−3) to 0.96 (θ = 0.6 m3 m−3). The root mean square deviation values of estimated and measured θ were 0.062 m3 m−3 for α = f(θ), 0.073 m3 m−3 for α = 0.977, 0.080 m3 m−3 for α = 0.938, and 0.136 m3 m−3 for α = 1.38. Therefore, for these set of soils the α‐variable approach and the constant ones using 0.977 and 0.938 presented the best estimation for the soil water retention relationships.

Summary Wood density measurement is related to several factors that influence wood quality. In this paper, a CT image calibration procedure which allows image quantification in terms of dry bulk density is presented for three different X- and gamma-ray energies (28.3, and 59.5, and 662.0 keV). The mass attenuation coefficients measured for a set of eight wood species did not vary significantly, allowing a single calibration for determination of bulk density of air-dried wood samples at each energy. The equation for bulk density calibration obtained was validated using a second set of twelve wood species. Comparison of bulk density determined by CT images, using the calibration procedure proposed, with values obtained by gravimetric methods, presented a very good linear correlation coefficient (R2=0.94). The main advantage of CT imaging over conventional techniques for wood bulk density determination is that it allows detection and quantification of heterogeneities and internal defects. At the sub-millimetric spatial resolution level, it is possible to identify morphological and structural aspects of wood samples.

The objective of the presented study was to develop a single probe Watson et al., 1975; Cheng et al., 1975; Arya et al., that can be used to determine soil water retention curves in both 1975; Royer and Vachaud, 1975; Simmons et al., 1979; laboratory and field conditions, by including a coiled time domain Gardner et al., 2001). Disadvantages of field estimation reflectometry (TDR) probe around the porous cup of a standard tensiometer. The combined tensiometer-coiled TDR probe was con-of soil water retention curves are related to the considerstructed by wrapping two copper wires (0.8 mm diam. and 35.5 cm able time effort involved and instrumentation required, long) along a 5-cm long porous cup of a standard tensiometer. The and the relatively small range of soil water matric potendielectric constant of five different soils (Oso Flaco [coarse-loamy, tials that can be measured with a tensiometer (Bruce and mixed Typic Cryorthod-fine-loamy, mixed, mesic Ustollic Haplargid], Luxmoore, 1986). In addition, h and measurements Ottawa sand [F-50-silica sand], Columbia [Coarse-loamy, mixed, sugenerally pertain to different soil volumes, making their peractive, nonacid, thermic Oxyaquic Xerofluvents], Lincoln sandy interpretation difficult and uncertain. loam (sandy, mixed, thermic Typic Ustifluvents), and a washed sand-More recently, TDR has been used in combination SRI30) was measured with the combined tensiometer-coiled TDR with tensiometer and electrical resistance techniques to probe (coil) as a function of the soil water content () and soil water determine in situ soil water retention curves. Baumgartmatric potential (h). The measured dielectric constant (ε coil) as a function of water content was empirically fitted with a third-order poly-ner et al. (1994) and Whalley et al. (1994) combined shalnomial equation, allowing estimation of (h)-curves from the combined low stainless steel electrodes with a porous stainless steel tensiometer-coiled TDR probe measurements, with R 2 values larger material in a standard two parallel probe configuration than 0.98. In addition, the mixing model approach, adapted for the tenfor simultaneous in situ measurement of and h. Prelimsiometer-coiled TDR probe, was successful in explaining the funcinary results showed its functionality and effectiveness, tional form of the coiled TDR data with about 30% of the coiled-TDR but limitations were related to the difference in meaprobe measurement explained by the bulk soil dielectric constant. This sured soil volume between and h measurements of this new TDR development provides in situ soil water retention data from probe. Simultaneous measurement of and h was also simultaneous soil water matric potential and water content measuresuggested by Noborio et al. (1999) using a TDR probe ments within approximately the same small soil volume around the partially embedded in a porous gypsum block. Assumcombined probe, but requires soil specific calibration because of slight desaturation of the porous cup of the tensiometer.

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