Mass transfer from and through packaging materials

The use of polymer films for food packaging requires a knowledge of their transport properties under varying conditions. The permeability to gases and water vapour of the packaging films at the specific conditions of use, i.e. temperature, relative humidity and pressure gradient, are needed for selecting the optimum packaging system to ensure the required shelf-life of the packed product. Migration from, and absorption by, plastic films also play an important role in their selection. The 0₂ and CO₂ permeabilities of three plastic films at four different temperatures were evaluated and shown to follow the Arrhenius relationship in the range tested. The effects of four thicknesses of one film on its permeability are also reported. Three methods to evaluate migration from polymeric films were compared using different weight/volume ratios. The extraction method recommended by the FDA, using n-hexane in a stirred flask, was found to be best. The shelf-life of Matzoth (Jewish Passover bread) packed in polyethylene (stored at 25°C) was found to be longer than the shelf-life of those packed in the higher barrier PVDC/PE. This was apparently due to the absorption of undesirable oxidation compounds, given off from the Matzoth by the PE, which were not absorbed at detectable levels by the PVDC/PE.     

Interferometric polarization mode dispersion measurements withfemtosecond sensitivity

The standard interferometric measurement technique for polarization mode dispersion (PMD) measures the cross correlation of the electromagnetic field at the output of the fiber or optical device under test when a broadband light source is used. The sensitivity (smallest measurable PMD delay) of this technique is limited by the coherence time of the light source. In this contribution, we critically analyze extensions of the interferometric technique to lower values and present a new extension which provides a sensitivity of a few femtoseconds     

Optical fiber characterization by simultaneous measurement of thetransmitted and refracted near field

An experimental setup is presented which permits, in a routine way for R&D purposes, simultaneous measurement of the transmitted near field at 1300 nm and 1550 nm, and the refracted near field at 820 nm. A new method for the calibration of the refractive index is proposed. The obtained accuracy for the refractive index is dn±0.0002. The reproducibility of measurements of geometrical parameters like the mode field diameter, the core and cladding diameters, and concentricity error, is ±0.1 μm. Measurements of the mode field as a function of polarization state for four different hi-bi fiber are presented     

Mass action and polynomial optimization

An analogy between the law of mass action and generalized polynomial optimization is proven, interpreted, and illustrated numerically. The example, which involves finding optimal temperatures in three chemical reactors in series, has been solved previously by other optimization methods. In this case the theory leads to insight into the structure of the optimum rather than to improved computational procedures.     

Experiments with solid fuel for a pulsed co2 gas dynamic laser

Experiments with solid fuel for a pulsed CO₂ gas dynamic laser are reported. The oxidation of solid cyanurictriazide, C₃N₁₂, was carried out by solid hexanitroethane under vacuum or in nitrogen atmosphere, and by the gaseous oxidants N₂O diluted in N₂ or in air. The best results are achieved by combustion of cyanurictriazide in air. The laser output energy from this solid fuel is equivalent to that achieved by gaseous fuel, at the same experimental lasing conditions.     

Coherent reflectometry of optical fiber amplifiers

The reflectivity of commercially available erbium-doped fiber amplifiers (EDFAs) was measured with coherent optical frequency domain reflectometry (C-OFDR). Reflections at the output isolator as well as the distributed gain along the erbium-doped fiber could be observed thanks to the high amplified spontaneous emission (ASE) rejection due to the coherent detection. Gain figures obtained with the OFDR technique are in good agreement with single-pass direct gain measurements.     

Mid-range coherent optical frequency domain reflectometry with aDFB laser diode coupled to an external cavity

The optical frequency of an external double cavity coupled laser diode was controlled via the phase of the feedback light. Strong linewidth and mode hopping reductions were obtained, extending coherent reflectometry with semiconductor sources to the range of hundreds of meters