We study the existence of renormalized solutions for a class of nonlinear degenerated parabolic problem. The Carathéodory function satisfying the coercivity condition, the growth condition and only the large monotonicity. The data belongs to L^1(Ω). 相似文献
Air monitoring networks are necessary to assess air quality in order to reduce pollution to levels which minimise harmful effects on human health and the environment. This paper describes a method to design air quality monitoring networks for nitrogen dioxide and ozone and its application in Cordova, Andalusia, southern Spain. The city has a population of 325,453 inhabitants and traffic is its main source of air pollution. The first step of this method made it possible to determine from historical data that two control stations for NO2 and one control stations for O3 are necessary according to the legislation. Sampling campaigns with passive diffusion samplers at 81 sites were then carried out to obtain information on the pollution distribution in Cordova. The sampling campaigns in 2001–2002 revealed an average concentration of 19.5 μg/m3 for NO2 with maximum values up to 28.6 μg/m3 in Cordova city centre. The average ozone concentrations were recorded downwind from the emission source, reaching 91.8 μg/m3; the average ozone value in Cordova was 65.3 μg/m3. After spatial interpolation of the obtained values with Geographical Information Systems, a selection of the best locations for the monitoring stations was made, in line with the macro- and microscale siting requirements of the European Directive 2008/50/EC on ambient air quality and cleaner air for Europe. A second sampling campaign with diffusive samplers was carried out in 2007 to control if the locations of the air quality assessment stations were still representative for their zone. 相似文献
A general synthetic route to 1-alkyl and 1,3-dialkyl-2-benzimidazolones from 1-alkenyl-2-benzimidazolones using phase-transfer catalysis conditions is described. 相似文献
Initially developed as an elastomer with an excellent record of barrier and chemical resistance properties, poly(disulfide) has experienced a revival linked to the dynamic nature of the S–S covalent bond. A novel photobase‐catalyzed oxidative polymerization of multifunctional thiols to poly(disulfide) network is reported. Based solely on air oxidation, the single‐step process is triggered by the photodecarboxylation of a xanthone acetic acid liberating a strong bicyclic guanidine base. Starting with a 1 μm thick film based on trithiol poly(ethylene oxide) oligomer, the UV‐mediated oxidation of thiols to disulfides occurs in a matter of minutes both selectively, i.e., without overoxidation, and quantitatively as assessed by a range of spectroscopic techniques. Thiolate formation and film thickness determine the reaction rates and yield. Spatial control of the photopolymerization serves to generate robust micropatterns, while the reductive cleavage of S–S bridges allows the recycling of 40% of the initial thiol groups.
Flash vacuum pyrolysis (FVP) of 1,7‐bis‐(3‐aroylideneamino)‐4,6,10,12‐tetramethyl‐2,8‐dioxo‐1,7‐diazacyclododeca‐3,5,9,11‐tetraene‐3,9‐dicarbonitriles 11a‐c at 650°C and 0.02 Torr yielded 5,7‐dimethyl‐3‐(4‐methylbenzoyl)‐pyrazolo[1,5‐a]pyridine‐4‐carbonitrile 14 , 4,6‐dimethyl‐2‐oxo‐1,2‐dihydropyridine‐3‐carbonitrile 16 and 3‐aryl‐3‐oxo‐propionitriles 17a,b . A plausible mechanism is suggested to account for the formation of the products. 相似文献
The hydrolysis of distannylated compounds in which the tin atoms are linked by an organic spacer has been studied under microemulsion conditions using dynamic light scattering and infrared spectroscopy. The experiments provided evidence that the growth of hybrid material particles occurs in the aqueous phase, outside the organic phase of the microemulsion. The growth rates of the particles were found to be strongly dependent on the nature of the spacers, a polymethylene chain inducing the fastest process. This different behavior was explained by a slower condensation process rather than a slower hydrolysis. The high surface areas measured for the hybrid materials could be explained by a possible coating of the hybrid particles by surfactant molecules, thus preventing either their growth or their aggregation. 相似文献
The main objective of this work was to contribute to the reduction in the contamination of phenolic compounds contained in margin by an adsorption process on two types of raw bentonite. The margin used in the studies was collected from a semi-modern oil mill located in the Nador–Morocco region. The results of the physico-chemical analyses showed that the effluents of the oil mills showed that they are highly polluted, particularly in terms of the total suspended solids (TSS), chemical oxygen demand (COD), and iron content of around 154.82 (mg/L), and copper content of 31.72 (mg/L). The mineralogy of bentonites studied by X-ray diffraction (XRD) reveals the existence of two types of montmorillonite; theoretically, the diffraction peak (001) of the montmorillonite appears at 15 Å, with a basal spacing that corresponds to a calcium pole, and the diffraction peak (001) appears at 12Å, with a basal spacing that corresponds to a sodium pole. The specific surface area of the bentonite used is characterized by a large specific surface area, varying between 127.62 m2·g−1 and 693.04 m2·g−1, which is due to the presence of hydrated interleaved cations. This surface is likely to increase in aqueous solution depending on the solid/liquid ratio that modulates the degree of hydration. With a high cation exchange capacity (CEC) (146.54 meq/100 g), samples of margin mixed with raw bentonites at different percentages vary between 5% and 100%. The potential of Moroccan bentonite for the phenol adsorption of 9.17 (g/L) from aqueous solutions was investigated. Adsorption tests have confirmed the effectiveness of these natural minerals in reducing phenolic compounds ranging from 8.72% to 76.23% contained in the margin and the efficiency of heavy metal retention through microelements on raw bentonites. The very encouraging results obtained in this work could aid in the application of adsorption for the treatment of margin. 相似文献