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71.
Nitrogen solubilities in the CaO—CaF2 system were determined under controlled oxygen partial pressures as well as at carbon saturation. Nitrogen contents (as N3?) were shown to strongly depend on oxygen partial pressure from 10?11 to 10?13 atm. At carbon saturation both nitride and cyanide contents are also dependent on oxygen partial pressure, i.e. CO partial pressure. The dependence of nitride and cyanide contents on nitrogen partial pressure was found to be compatible with the theory and is described by the equations proposed in this paper. The results are also discussed in terms of nitride and cyanide capacities for a better understanding of the dissolution of nitrogen in slags of different composition. The temperature dependence of nitride content showed an increase in nitride content with increasing temperature. 相似文献
72.
A preventive maintenance policy for a standby system subject to internal failures and external shocks with loss of units 总被引:1,自引:0,他引:1
Juan Eloy Ruiz-Castro 《International journal of systems science》2013,44(9):1600-1613
In many situations, serious damage and considerable financial losses are caused by non-repairable failures of a system. Redundant systems and maintenance policies are commonly employed to improve reliability. This paper is focused on the modelling of a complex cold standby system by analysing the effectiveness and costs of preventive maintenance, always in an algorithmic form. The online unit of the system is subject to wear failures and external shocks. The online unit can go through an indeterminate number of degradation levels before failure. This one is observed when inspections occur. Inspections are performed at random intervals, and when one takes place, the unit is taken to the preventive maintenance facility if it is necessary. The preventive maintenance time and cost is different depending on the degradation level observed. If only one unit is performing, a minimal maintenance policy is adopted in order to optimise system behaviour. Reliability measures such as the conditional probability of failure are worked out in a well-structured and algebraic form in transient and stationary regimes by using algorithmic methods. The stationary distribution is calculated using matrix analytic methods, and rewards are included in the model. An optimisation example shows the versatility of the model presented. 相似文献
73.
P. Ciambelli D. Sannino V. Palma V. Vaiano P. Eloy F. Dury E.M. Gaigneaux 《Catalysis Today》2007,128(3-4):251-257
The photocatalytic properties of sulphated MoOx/γ-Al2O3 catalysts in cyclohexane oxidative dehydrogenation have been determined in a two-dimensional fluidized bed photoreactor and compared to those of sulphated MoOx/TiO2 catalysts. Photocatalytic tests on MoOx/γ-Al2O3 at 8 wt% MoO3 and various sulphate contents showed the selective (100%) formation of cyclohexene, without production of benzene, as instead found with MoOx/TiO2. These results show that the selectivity of photocatalytic cyclohexane oxydehydrogenation is dramatically influenced by the catalyst support.
Maximum cyclohexane conversion and cyclohexene yield of 11% were obtained for SO4 content of 2.6 wt% at 120 °C. Physico-chemical characterisation of catalysts indicates the presence of both octahedral polymolybdate and sulphate species on alumina surface, as previously found for titania. Increasing sulphate load, thermogravimetry evidenced the presence of up to three sulphate species at different thermal stability. The lower activity observed at high sulphate content is likely due to polymolybdate decoration by sulphates. 相似文献
74.
Magnetic Actuation: Voltage‐Induced Coercivity Reduction in Nanoporous Alloy Films: A Boost toward Energy‐Efficient Magnetic Actuation (Adv. Funct. Mater. 32/2017) 下载免费PDF全文
75.
Zouhair Boukha José María Sánchez-Amaya Leandro González-Rovira Eloy Del Rio Ginesa Blanco Javier Botana 《Metallurgical and Materials Transactions A》2013,44(13):5711-5723
In this study, AA5083 samples were butt welded under a conduction regime with high-power diode laser (HPDL). Various mixtures composed of Ar and CO2 were used as a shielding gas. The influence of the shielding gas composition on the microstructure and on the properties of laser welds was analyzed. The weld beads were deeply characterized by metallographic/microstructural studies, X-ray diffraction (XRD), X-ray energy dispersive spectrometry (X-EDS) chemical analyses, X-ray photoelectron spectra (XPS), microhardness, and tensile strength. The corrosion resistance of laser-remelted surfaces with different CO2/Ar ratios was also estimated by means of electrochemical tests. The addition of CO2 to the shielding gas results in a better weld penetration and oxidizes the weld pool surface. This addition also promotes the migration of Mg toward the surface of weld beads and induces the formation of magnesium aluminates spinel on the welds. The best corrosion resistance result is achieved with 20 pct CO2. The overall results indicate that the addition of small percentage of CO2 to Ar leads to improvements of the mechanical and corrosion properties of the aluminum welds. 相似文献
76.
77.
Babot JD Hidalgo M Argañaraz-Martínez E Apella MC Perez Chaia A 《International journal of food microbiology》2011,145(1):221-228
The classical or dairy propionibacteria have well-documented industrial applications and have been proposed for probiotic applications. Given their industrial importance it is necessary to employ fast and reliable techniques to monitor the growth during products elaboration, industrial fermentations or the intestinal transit. Therefore, the aim of this investigation was to design oligonucleotide probes targeting the 16S rRNA of dairy propionibacteria and optimise the fluorescence in situ hybridization (FISH) protocol to detect these bacteria. Two specific probes were in silico designed to detect Propionibacterium freudenreichii and P. jensenii, named Pfr435 and Pj446 respectively. The FISH protocol was optimised for the hybridisation of propionibacteria cells with the universal probe Eub338 and the designed probes. These probes were assayed in situ for their specificity to hybridise species of propionibacteria by observation using fluorescence microscopy and results were compared with the probe Pap446 previously designed for P. acidipropionici. Probes Pap446, Pfr435 and Pj446 were also evaluated by fluorescence spectrophotometry to assess the influence of cells physiological state during growth in batch culture in the fluorescence intensity. The maximum fluorescence intensity was observed at the onset of the stationary phase of growth and was then reduced. However, changes on the cells permeability did not reduce the efficiency of 16S rRNA hybridisation with the fluorescence-labelled probes. Propionibacteria counts obtained by FISH and plate count methods were compared in a commercial Gruyère cheese. The results showed that this method can be used as a rapid technique for the enumeration of these bacteria in cheese samples. 相似文献
78.
Montserrat Tobajas Eloy García-Calvo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1996,66(2):199-205
A simple theoretical model is used to describe hydrodynamic behaviour in bubble columns. The model is based on an energy balance which takes into account the energy dissipation in the liquid motion and the energy dissipation at the gas–liquid interface. Gas hold-up, liquid velocity at the column axis and radial profile of liquid velocity are predicted in a wide range of operating conditions (JG up to 1·452 m s−1) and column sizes (D = 0·1–1 m and H = 1·22–9·5 m) with good accuracy. Predictions of liquid velocity are also compared with one of the most widely accepted models. 相似文献
79.
María Elena Monroy Vázquez José Rodolfo García Eloy Solano Huitziméngari Campos Eduardo García 《臭氧:科学与工程》2017,39(2):104-114
Protocols for seed germination in the Opuntia genus are different and unsuitable for all their species. Dormancy of Opuntia seeds can be modified by the combination of scarification and an oxidizing agent such as O3, which could induce antioxidant and DNA-repair mechanisms or dormancy-breaking effects in hydrated seeds. The objective of this study was to evaluate the effects that the combination of mechanical and chemical scarification with exposition to sub-lethal O3 doses have on seed germination and seedling growth of O. streptacantha Lem., O. megacantha Salm-Dyck, and O. ficus-indica (L.) Mill. Our hypothesis was that O3 favors germination on scarified seeds and that the magnitude of the effect is species-dependent. Water uptake and germination were quantified in seeds every 48 h, until their roots reached a 5-mm length. The results were analyzed with an analysis of variance and multiple means comparisons with the Tukey test. Accelerated water uptake was observed during the first 48 h; the maximum average was 33.5% in all species. The combination of acid scarification and imbibition in the presence of O3 increased (P ≤ 0. 05) germination (between 17.8 and 44.4%), mainly in O. streptacantha. O3 increased germination, regardless of the species. O3 can be used in sublethal doses to increase seed germination and seedling development in Opuntia genus. 相似文献
80.
Javier Santiago-Morales María José Gómez Sonia Herrera-López Amadeo R. Fernández-Alba Eloy García-Calvo Roberto Rosal 《Water research》2013
This study aims to assess the removal of a set of non-polar pollutants in biologically treated wastewater using ozonation, ultraviolet (UV 254 nm low pressure mercury lamp) and visible light (Xe-arc lamp) irradiation as well as visible light photocatalysis using Ce-doped TiO2. The compounds tracked include UV filters, synthetic musks, herbicides, insecticides, antiseptics and polyaromatic hydrocarbons. Raw wastewater and treated samples were analyzed using stir-bar sorptive extraction coupled with comprehensive two-dimensional gas chromatography (SBSE–CG × GC–TOF–MS). Ozone treatment could remove most pollutants with a global efficiency of over 95% for 209 μM ozone dosage. UV irradiation reduced the total concentration of the sixteen pollutants tested by an average of 63% with high removal of the sunscreen 2-ethylhexyl trans-4-methoxycinnamate (EHMC), the synthetic musk 7-acetyl-1,1,3,4,4,6-hexamethyltetrahydronaphthalene (tonalide, AHTN) and several herbicides. Visible light Ce–TiO2 photocatalysis reached ∼70% overall removal with particularly high efficiency for synthetic musks. In terms of power usage efficiency expressed as nmol kJ−1, the results showed that ozonation was by far the most efficient process, ten-fold over Xe/Ce–TiO2 visible light photocatalysis, the latter being in turn considerably more efficient than UV irradiation. In all cases the efficiency decreased along the treatments due to the lower reaction rate at lower pollutant concentration. The use of photocatalysis greatly improved the efficiency of visible light irradiation. The collector area per order decreased from 9.14 ± 5.11 m2 m−3 order−1 for visible light irradiation to 0.16 ± 0.03 m2 m−3 order−1 for Ce–TiO2 photocatalysis. The toxicity of treated wastewater was assessed using the green alga Pseudokirchneriella subcapitata. Ozonation reduced the toxicity of treated wastewater, while UV irradiation and visible light photocatalysis limited by 20–25% the algal growth due to the accumulation of reaction by-products. Three transformation products were identified and tracked along the treatments. 相似文献