Superparamagnetic relaxation evidences large surface contribution for the magnetic anisotropy of MnFe<Subscript>2</Subscript>0<Subscript>4</Subscript> nanoparticles of ferrofluids

Manganese ferrite nanoparticles, in the size range 3.3–9.0 nm, are prepared by a hydrothermal coprecipitation process and peptized in aqueous solution. The magnetization curves recorded at room temperature on diluted colloidal sols allow characterizing the distribution of magnetic moment by using a simple Langevin formalism. Mössbauer spectroscopy measurements performed on powder samples at 77 K exhibit a quadrupolar doublet which intensity grows at the expense of the hyperfine sextet pattern as the nanoparticles mean size decreases. The magnetic dynamics behavior is then investigated by measurements of magnetic hysteretic properties at 5 K and temperature dependence of the zero field cooling (ZFC) susceptibility. The values found for the effective anisotropy constant and the dependence of the irreversibility field, inversely proportional to the reference size, clearly indicate that the magnetic anisotropy of our nanoparticles finds its origin on the disordered surface layer.     

Radar image texture as a function of forest stand age

Data on forest variables are required for environmental and forest management applications. Numerous authors have shown significant correlations between mean radar response intensity and forest variables (age, height or biomass) but few studies have explored the spatial characteristics of the radar response for varying forest states. In this Letter, variation in the most commonly used texture features is shown as a function of an indicator of forest growth (age) for a controlled homogeneous test site (monospecific, even‐aged forest, with identical sylvicultural practices and a sampling that covers all forest stages from sowing to harvest). Significant linear relationships between some texture features and stand age are observed. Moreover, the quality of some fits indicates that texture could be used instead of the usual intensity–age relationships that saturate for mature stands.     

Pulsed Eddy Current Technology: Characterizing Material Loss with Gap and Lift-off Variations

Abstract

Ownership costs of operational aircraft have increased steadily over the years. One of the major cost drivers is structural deterioration due to corrosion. Beyond the economics, finding and characterizing corrosion is essential for the continued airworthiness of aircraft fleets. To this end, the pulsed eddy current technique holds the potential of becoming the primary means of detecting corrosion in multilayered structures. Its wide-band frequency spectrum allows the determination of a large number of parameters, such as defect size and location. Pulsed eddy current is still considered an experimental nondestructive technique because of realistic inspection problems (e.g., probe tilting, protrusion of rivets, and thickness variations in adhesive and paint) have not been addressed in the past. Recent advances change this situation and allow pulsed eddy current to be a credible field technique.     

Scattering from several test-objects computed by 3-D hybrid IE/PDEmethods

The electromagnetic scattering from composite anisotropic dielectric and conducting structures is modeled by hybrid partial differential equation-integral equation formulations. We emphasize the role of edge elements for both the partial differential equation and the integral equation discretization and for the coupling of the two. Numerical results from the various formulations are presented and measurements are compared in order to obtain test cases for the development and validation of numerical methods     

Fictive temperature measurement of single-mode optical-fiber coreand cladding

The fictive temperatures of single-mode optical-fiber core, along with its inner and outer cladding, were measured using an infrared (IR) reflection method on the fiber cross-sectional surface. To allow for usage of a larger IR beam size than the diameter of the fiber core, the cross-sectional area of the fiber was increased by slicing the fiber at an oblique angle, along approximately 3° off the fiber axis direction. The magnitude of the fictive temperature was estimated from the IR peak wavenumber-fictive temperature relation obtained for bulk glasses with the same compositions. The observed fictive temperature was in the range of 1150~1300°C for the core, 1450~1550°C for the inner cladding, and 1620~1660°C for the outer cladding and exhibited good correlation with the fiber cooling rate     

Phase Diagram, Short-Range Structure, and Amorphous Phases in the ZrO2-GeO2(-H2O) System

Gels of the ZrO₂-GeO₂(-H₂O) system have been prepared via the hydrolysis-polycondensation of zirconium and germanium isopropoxides. Phase relationships have been deduced from differential thermal analysis, thermogravimetric analysis, and shrinkage analysis and are discussed on the basis of X-ray diffractometry and Raman scattering studies. Emphasis has been given to understanding the short-range structure. A small glass-forming domain is observed in the temperature range of 600°−700°C for compositions of 30–40 mol% GeO₂.     

Polylactide (PLA)—a new way of production

Poly(lactide) (PLA), a biodegradable aliphatic polyester with excellent properties for different polymer applications, has been used mostly in the biomedical field, mainly because of its high price, resulting from expensive polymerization and purification techniques. Although this polymer can play a major role in future markets for biodegradable polymers, the current high price has to be reduced significantly to at least $4 US/kg. Therefore, this paper aims to partially review the polymerization techniques traditionally used in PLA synthesis and to propose new developments that enable us to produce these polymers by an innovative process for just a portion of the costs traditionally charged, using reactive extrusion techniques in a closely intermeshing co-rotating twin screw extruder. This paper gives an overview of attainable mechanical properties and future markets.