多视极化SAR图象相干斑抑制的研究

本文研究多视极化合成孔径雷达(SAR)图象的相干斑抑制,提出多视极化白化滤波(MPWF)法,并进一步将它发展成具有多通道输出的全极化滤波器。本文还定量地分析了MPWF方法抑制相干斑的能力,并在理论上同全功率法、加权法和功率均衡法进行了比较。应用NASA/JPL机载L波段四视全极化SAR数据的试验结果验证了所提方法的有效性和优越性,也说明了MPWF处理能显著地提高SAR图象的分类精度。     

Microbiological and physicochemical characteristics of Cameros cheese

Eighteen samples of Cameros cheese, a fresh Spanish goat's cheese, were collected from the four different producers of this regional kind of cheese. Physicochemical and microbiological analyses were carried out to evaluate the sanitary quality and the physicochemical characteristics of the product. The influence of the season of the year and the elaboration conditions were also studied. Cameros cheese is a fat cheese (54·2±6·5% of total solids; TS), with a high pH close to the neutrality (6·35±0·14), high moisture (TS value of 42·5±4·7%) and low salt content (0·78±0·30% of TS). Listeria monocytogenes was found in 5·6% of samples. Staphylococcus aureus counts above 2 log cfu g⁻¹were found in 55% of the cheeses studied. Thirty-three percent of the April samples and 67% of the July samples reached microbiological levels above the legally established standards. None of the samples yieldedSalmonella spp. The dairy had a significant effect on salt content (P<0·001) because different salt application methods were applied. Also significant differences (P<0·01) of S. aureus counts were detected among the different dairies. Significant seasonal differences of non-protein nitrogen (P<0·01) were detected. The season significantly affected the counts of Enterobacteriaceae (P<0·01), mesophilic micro-organisms and psycrotrophs (P<0·05) and yeast and mould counts (P<0·05).     

Thermal stability of P(HB‐co‐HV) and its blends with polyalcohols

The thermal stability of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [P(HB‐co‐HV)] and its blends with poly(propylene glycol)s (PPGs) and castor oil (CO) is reported. The study includes the determination of the degradation kinetics of these materials and the analysis of the effects of the degradation on the mechanical properties and crystallization behavior. Spectroscopy (¹H‐NMR, FTIR), differential scanning calorimetry (DSC), thermogravimetry, and tensile testing techniques are used for the experimental analysis. A chain‐scission degradation mechanism is confirmed by the formation of vinyl groups. Two temperature ranges are investigated. In the range closest to the melting point, 100–200°C, where the blend does not exhibit weight reduction, a fast and sensible loss of molecular weight and tensile strength was detected. The second temperature range, 200–400°C, is characterized by mass loss by pyrolysis. In this range, different kinetic models of the degradation process are proposed. Polyalcohol addition produces opposite effects, while the addition of PPG enhances the degradation of P(HB‐co‐HV). When CO is added, the thermal stability of the blend increases. Mechanical properties of the blends before and after degradation were determined. The tensile modulus increases at the first step of degradation and decreases with the degradation time. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2889–2900, 2000     

Kinetic analysis of the thermal degradation of PVC plastisols

The thermal degradation of plasticized polyvinyl chloride (plastisol) is reported here. Plastisols used in the present work were prepared with the plasticizer diethylhexyl phthalate in different proportions. Thermogravimetric analysis has been applied to study the behavior of plastisols at high temperatures and to evaluate their degradation kinetics. Several tests were carried out at different heating rates and the variation of the degree of reaction with time and temperature was calculated. The influence of the heating rate in dynamic measurements (5–40°C/min) on kinetic parameters, such as activation energies and reaction orders, has also been studied. These parameters were calculated from dynamic thermogravimetric analysis tests using Friedman analysis and a kinetic model for the degradation of poly(vinyl chloride) and plastisols has been then developed. The obtained model was able to simulate the thermal degradation process of plastisols in dynamic conditions and was used to evaluate the effects of additives in the degradation. The results of this study can be used to optimize the concentration of plasticizers and stabilizers in poly(vinyl chloride) formulations. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1069–1079, 1999     

Monitoring network for online diagnosis of power generators

A monitoring network developed to diagnose early faults in power generators is described. Nowadays, the appropriate operation of generators resides in the information provided by the online monitoring system, which is used to implement predictive maintenance for these machines and to provide early warning of potential failures.In this paper, the configuration of the monitoring system and a detailed study of the measured variables related to their physical behaviour within the generators’ operation are presented. The sensors used and the waveform analysis procedures are explained. Additionally, the architecture that constitutes the application programs and their characteristics as a data network is also described. Finally, some results recorded by the system are shown and discussed.     

Effect of lactobacillus adjunct cultures on the microbiological and physicochemical characteristics of Roncal-type ewes'-milk cheese

The effect of two different experimental adjunct cultures composed of native facultatively heterofermentative lactobacilli (FHL) on the development of various groups of micro-organisms in Roncal-type ewes' milk cheese was studied. Four cheese batches were manufactured from raw milk (C), pasteurized milk (P), pasteurized milk and an adjunct culture of Lactobacillus paracasei (PP); and pasteurized milk and adjunct culture of Lactobacillus paracasei plus Lactobacillus plantarum (PPP). Retention of the two adjunct cultures in the cheeses was good, and population levels remained constant at around 10(7) cfu g(-1) of cheese throughout ripening. Levels of Enterobacteriaceae and enterococci fell off more abruptly in the batches made with the Lactobacillus adjunct cultures, suggesting competition between the added lactobacilli and those groups of micro-organisms. The inhibitory effect was greater for the adjunct culture composed of L. paracasei plus L. plantarum. Lactococcal levels were higher in the batches made with added FHL, which may be indicative of a synergistic effect between these two groups.     

Factors influencing proportion and composition of CLA in beef

Bovine meat is criticised for the bad nutritional image of its lipids and fatty acids. However, with dairy products, beef is the major source of conjugated linoleic acid (CLA) which could have several human health benefits. The present study compared, from data of five nutritional experiments on bovine animals performed by the laboratory, the impact of factors linked to the animals (breed, age, sex, type of muscle) and to feeding conditions (basal diet, lipid supplements) on the CLA proportion and composition in muscles. Among these factors, linseed supplementation was an efficient way to increase CLA proportion in beef (+22% to +36%) but was highly modulated by the nature of the basal diet, and by intrinsic factors (breed, age/sex, type of muscle) since these ones could modulate CLA proportion in beef from 24% to 47%. Moreover, these factors modified also the proportion of cis,trans-CLA, related to cis,cis- and trans,trans-isomers. Specific biological properties of these latter isomers should be determine to understand the consequences of intramuscular CLA isomer variations for the health of consumers.