Radiative heat transfer in porous media with spatially-dependent heat generation

We report an investigation of radiative heat transfer in porous radiant burners. The combustion was modeled as a spatially-dependent heat generation. Using the spherical harmonics to solve the equation of transfer, we have obtained the P-11 solution for the net radiative heat flux. Results presented illustrate the radiant output as a function of the position of the combustion zone, the optical thickness and the type of scattering of the porous layer, and the amount of reflection from the distribution chamber.     

Effect of organic poultry purchase frequency on consumer attitudes toward organic poultry meat

Because of the growing consumers' interest in organic meat, consumers' (N = 976) attitude toward organic meat was evaluated. Most respondents (59%) occasionally purchased organic chicken. To determine the organic chicken consumer profile, the organic chicken consumption frequencies of different demographic groups were compared. The results show dependence on age (P= 0.039) and ethnicity (P = 0.015). Older respondents as well as respondents who identified themselves as Caucasians tended to buy organic chicken more frequently. However, many other socio-demographic factors were not correlated with organic chicken consumption: gender (P = 0.185), education (P = 0.235), household income (0.867), living with partner or not (P = 0.235), and number of children (P = 0.883). Taste was identified as the most important meat quality attribute (perceived as [very] important by 94% of the respondents). Other important meat quality criteria were: general appearance, overall health, price, nutritional value, and containing no medical residues. "Organically produced" appeared to not be that important compared with other criteria. When respondents bought organic chicken more often, the importance of most of the meat quality attributes shifted to higher levels of importance, except for the price where an adverse effect was shown. The main motivation factors to buy organic chicken were the perception that organic chicken has fewer residues (pesticides, hormones, antibiotics), is safer, and healthier. The high price for organic meats was the strongest limiting factor for organic meat purchases followed by poor availability. Approximately 41% of the non-buyers and 30% of the occasional buyers perceived organic meat as not or hardly likely to be available in their supermarket. PRACTICAL APPLICATION: This study obtained a better knowledge of consumers' attitudes and perception of organic chicken as well as the effect of various demographics on the likelihood of buying organic chicken. For marketing purposes of organic meats, it helps to know which attributes consumers perceive as important, where the consumer purchases organic chicken, and what the perceived availability of organic chicken is. Additionally, the motivation and deterrent factors are described indicating why the consumer does or does not purchase organic chicken. This information can be valuable to help promoting organic meats to the consumers.     

Relationship between Phenolic Acids Formed During Rumen Degradation of Maize Samples andin vitroDigestibility

The organic matter (OMD) and cell wall (CWD) digestibility of stalks of 25 different maize samples were determined in an in vitro assay using rumen fluid. The stalk OMD and CWD varied between 62–80% and 44–62%, respectively. The free phenolic acids formed in the liquid phase during fermentation in in vitro incubations were assessed by HPLC and ¹H NMR. The following nine phenolic acids could be demonstrated to be present: p -hydroxybenzoic (HBA), p -hydroxyphenylacetic (HPAA), vanillic (VA), syringic (SYRA), 3-(4-hydroxyphenyl)propionic (HPPA), p -coumaric (PCA), ferulic (FA), phenylacetic (PAA) and 3-phenylpropionic (PPA) acids. Large variation was observed among the maize samples for all phenolic acids identified. The most abundant phenolic acids, PPA, PAA and HPAA were present in concentrations ranging from 0·57 to 1·41 mM, 0·32 to 0·46 mM, and 71 to 105 μM, respectively, and were present as free monomeric molecules. HBA concentrations ranged from 6·9 to 21·1 μM and this acid was also present as free molecules. The other phenolic acids could only be observed after NaOH treatment of the liquid phase and were detected in minor amounts (0 to 12 μM). Correlation studies revealed a negative relation between digestibility and NaOH labile esters in the medium (ie PCA, FA, VA and SYRA esters) and a positive relationship between digestibility and PPA and PAA. When path analysis was applied, an inverse effect of PCA esters in the medium on both OMD and CWD ( r =-0·71 and −0·56, respectively) was observed and a high positive effect of PPA acid on CWD ( r =+0·67). Principal component analysis revealed close associations between released phenolic acid esters, neutral detergent fibre, and cell wall esters of PCA and FA.     

Joining composite pipes using hybrid prepreg welding and adhesive bonding

A critical technology for composite piping systems in offshore platforms is the joining technique. This paper discusses the development of a hybrid joining approach by using heat‐activated prepreg welding and adhesive bonding. The joining procedure was demonstrated via specimens' fabrication. Four adhesives, with varying mechanical properties, were used to seal the gap between the two pipes. A glass fiber reinforced prepreg was used to wrap the pipes. A total of forty‐five specimens were prepared and evaluated using standardized internal pressure tests. A finite element analysis was conducted to aid in the understanding of the mechanisms of the hybrid joining method. Recommendations for further studies were made based on the test and finite element analysis results.     

Test‐data generation using genetic algorithms

This paper presents a technique that uses a genetic algorithm for automatic test‐data generation. A genetic algorithm is a heuristic that mimics the evolution of natural species in searching for the optimal solution to a problem. In the test‐data generation application, the solution sought by the genetic algorithm is test data that causes execution of a given statement, branch, path, or definition–use pair in the program under test. The test‐data‐generation technique was implemented in a tool called TGen, in which parallel processing was used to improve the performance of the search. To experiment with TGen, a random test‐data generator called Random was also implemented. Both Tgen and Random were used to experiment with the generation of test‐data for statement and branch coverage of six programs. Copyright © 1999 John Wiley & Sons, Ltd.