A process to recover carbon fibers from polymer-matrix composites in end-of-life vehicles

Because of their high strength-to-weight ratios, carbon-fiber-reinforced polymer-matrix composite (PMC) materials are being evaluated for use in the automotive industry. The major barriers to their widespread use are their relatively high cost and the uncertainty about whether they can be recycled. A process to recover carbon fibers from obsolete PMC materials has been developed at Argonne National Laboratory. The process was tested using PMC samples made with different thermoset or thermoplastic substrates. For most mixtures of PMCs, the process can be energy self-sufficient using the polymer substrate as an energy source. An evaluation of the recovered samples found that the fibers appear to have retained good properties and characteristics and are suitable for short fiber applications. This paper describes the process and the characteristics and properties of the recovered fibers. For more information, contact Bassam J. Jody, Argonne National Laboratory, 9700 S. Cass Ave, Building 362, Argonne, IL 60439; (630) 252-4206; fax (630) 252-1342; e-mail bjody@anl.gov.     

Effects of Pseudomonas chlororaphis and gaseous chlorine dioxide on the survival of Salmonella enterica on tomatoes

Control of Salmonella enterica on tomatoes is important for food safety. The aim of this research was to evaluate the survival of Salmonella enterica serovars Montevideo (SM) and Typhimurium (ST) on tomatoes exposed to gaseous chlorine dioxide and Pseudomonas chlororaphis (Pc). Pc was applied to stem scars of tomatoes prior to inoculations with SM and ST. Tomatoes were treated with gaseous ClO₂ at 0.4 mg L^?1 for 2 and 4 h (90% R.H. 13 °C), respectively. At 4 h of ClO₂ treatment, SM and ST populations were reduced to 0.82 and <0.30 log CFU g^?1, respectively. Tomatoes treated with SM and ST had 5.42 and 5.37 log CFU g^?1 of Salmonella. Tomatoes treated with Pc + Salmonella count was 2.59 (treated) and 5.83 log CFU g^?1 (control). Salmonella survival was similar at 2 and 4 h of ClO₂ treatment. Application of ClO₂ and Pc may reduce contamination of tomatoes by Salmonella serovars.     

Fat oxidation in freeze-dried grouper during storage at different temperatures and moisture contents

The effects of moisture content levels and storage temperature on the lipid oxidation in freeze-dried grouper were studied. Three trends were observed in the changes of PV (peroxide value) depending on the moisture content and storage temperature. An exponential rise of PV was observed (p < 0.05) at lower temperatures (−20 °C and 5 °C for samples at moisture 5 g/100 g; and −20 °C for samples at moisture 20 g/100 g). At temperatures 25 °C for samples at moisture 5 g /100 g, and 5 and 25 °C for samples at 20 g moisture/100 g peaks of PV were observed (p < 0.05). At higher temperatures (40 °C for both moisture content levels) an exponential decay instead of increase were observed (p < 0.05). Moisture content levels had no significant effect (p > 0.05) on PV stored at temperature of −40 °C. The monolayer moisture for freeze-dried grouper was estimated as 6.2 g/100 g dry solids using BET-isotherm. Differential scanning calorimetry (DSC and modulated DSC) thermogram line showed two shifts (i.e. glass transition) and two endothermic peaks, one for melting of oil and another for decomposition. The validity of the water activity and glass transition concepts were evaluated. It is concluded that glass transition concept may be used to explain the process more adequately.     

On robust performance in

In this paper we consider the robust performance problem in with scalar perturbations. We illustrate how the worst case performance can be regarded as an norm of a function of several complex variables. Based on this characterization we show how the worst case performance can be obtained from the norm of a single system. This system is constructed from the original nominal system with the perturbations replaced by certain all-pass functions. We show that as the order of the all-pass functions goes to infinity, this norm converges to the worst case performance. The implications of this characterization for computing the complex structured singular value and robust synthesis are discussed, though at present, this method does not seem to provide an efficient algorithm for this computation.     

On robust stability with structured time-invariant perturbations

We consider the problem of robust stability for uncertain systems described in terms of multiple scalar structured time-invariant perturbations, which are norm-bounded. The issue we address is the role that the type of perturbation norm plays in the robust stability conditions. To this end, the L^p-induced norm (for 1 ≤ p ≤ ∞) on the perturbations is considered, and it is shown that the structured singular value is the necessary and sufficient condition for robust stability for all these norms. We conclude that for time-invariant perturbations, in contrast to the time-varying case, robust stability conditions are independent of the type of perturbation norms.