The polycyclic aromatic hydrocarbons (PAH) in Egyptian condensates are analyzed for the first. A solid phase extraction (SPE) followed by gas chromatography-mass selective detection was used for their analysis. The method was calibrated for optimal extraction conditions. Excellent recoveries were found (78–114%) for the PAHs that were identified using a variety of standards and GC-MS spectra. The solid-phase extracted PAH fraction was further separated by HPLC on a Ag(I) mercaptopropanosilica gel to reduce the complexity of the sample by separating the PAHs based on the number of aromatic rings. The analytes were quantified using GC with a flame ionization detector. For this kind of sample SPE is a more convenient separation technique than an open column. PAHs containing two to four rings in the concentration range 0.6–11 μg/L were measured. Some preliminary geochemical hypotheses based on the analyzed PAHs and the previously analyzed S-containing aromatic compounds were formed as to the depositional environment and source rock type. 相似文献
Combustion of CO, ethyl acetate and ethanol was studied over CuOx/Al2O3, CuOx–CeO2/Al2O3, CuMn2O4/Al2O3 and Mn2O3/Al2O3 catalysts. It was found that modification of the alumina with ceria before subsequent copper oxide deposition increases the activity for combustion of CO substantially, but the effect of ceria was small on the combustion of ethyl acetate and ethanol. The activity increases with the CuOx loading until crystalline CuO particles are formed, which contribute little to the total active surface. The CuOx–CeO2/Al2O3 catalyst is more active than the CuMn2O4/Al2O3 catalyst for the oxidation of CO but the CuMn2O4/Al2O3 catalyst is more active for the combustion of ethyl acetate and ethanol.
Thermal ageing and water vapour in the feed caused a modest decrease in activity and did not affect the CuOx–CeO2/Al2O3 and CuMn2O4/Al2O3 catalysts differently. In addition, no difference in intermediates formed over the two catalysts was observed.
Characterisation with XRD, FT-Raman and TPR indicates that the copper oxide is present as a copper aluminate surface phase on alumina at low loading. At high loading, bulk CuO crystallites are present as well. Modification of the alumina with ceria before the copper oxide deposition gives well dispersed copper oxide species and bulk CuO crystallites associated to the ceria, in addition to the two copper oxide species on the bare alumina. The distribution of copper species depends on the ceria and copper oxide loading. The alumina supported copper manganese oxide and manganese oxide catalysts consist mainly of crystalline CuMn2O4 and Mn2O3, respectively, on Al2O3. 相似文献
Thermal spray processes are widely used to protect materials and components against wear, corrosion and oxidation. Despite
the use of the latest developments of thermal spraying, such as high-velocity oxy-fuel (HVOF) and plasma spraying, these coatings
may in certain service conditions show inadequate performance,e.g., due to insufficient bond strength and/or mechanical properties and corrosion resistance inferior to those of corresponding
bulk materials. The main cause for a low bond strength in thermalsprayed coatings is the low process temperature, which results
only in mechanical bonding. Mechanical and corrosion properties typically inferior to wrought materials are caused by the
chemical and structural inhomogeneity of the thermal-sprayed coating material. To overcome the drawbacks of sprayed structures
and to markedly improve the coating properties, laser remelting of sprayed coatings was studied in the present work. The coating
material was nickel-based superalloy Inconel 625, which contains chromium and molybdenum as the main alloying agents. The
coating was prepared by HVOF spraying onto mild steel substrates. High-power continuous wave Nd:YAG laser equipped with large
beam optics was used to remelt the HVOF sprayed coating using different levels of power and scanning speed. The coatings as-sprayed
and after laser remelting were characterized by optical microscopy and scanning electron microscopy (SEM). Laser remelting
resulted in homogenization of the sprayed structure. This strongly improved the performance of the laser-remelted coatings
in adhesion, wet corrosion, and high-temperature oxidation testing. The properties of the laser-remelted coatings were compared
directly with the properties of as-sprayed HVOF coatings and with plasma-transferred arc (PTA) overlay coatings and wrought
Inconel 625 alloy. 相似文献
This paper solves the fair and optimal house allocation problem (Sun and Yang, Econ Lett 81:73–79, 2003) when the agents preferences
are represented by nonlinear utility functions using techniques for global mixed integer nonlinear optimization. A small simulation
study indicates that if quasi-linear specifications are adopted as approximations to nonlinear utility functions and if the
fair and optimal allocation is identified based on this approximation, then the prices are typically higher on average and
the resulting allocation is typically non-fair. 相似文献
This paper describes industrial aspects of combined inventory management and routing in maritime and road-based transportation, and gives a classification and comprehensive literature review of the current state of the research.The literature is contrasted with aspects of industrial applications from a constructive, but critical, viewpoint. Based on the status and trends within the field, future research is suggested with regard to both further development of the research area and industrial needs. By highlighting the industrial aspects, practitioners will hopefully see the benefit of using advanced decision support systems in complex situations related to combined inventory management and routing in their business. In addition, a classification and presentation of the research should help and motivate researchers to further focus on inventory management and routing challenges. 相似文献
Do agglomerations stimulate productivity? An extensive literature on agglomeration economies, or urban increasing returns, has analyzed this question with aggregated spatial data. This paper estimates the relationship between agglomeration and productivity at the firm level using static and dynamic models. It makes use of a rich dataset comprising register information on all manufacturing firms in Sweden with 10 or more employees over the period 1997–2004. Three things emerge. First, firms located in larger regions are more productive when controlling for size, human capital, physical capital, ownership structure, import and export, industry classification, and time trend. Second, results from dynamic panel estimations suggests a learning effect in that agglomeration enhances firms’ productivity. Third, the role of agglomeration phenomena does not seem to have a clear coupling to firm size. 相似文献