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排序方式: 共有391条查询结果,搜索用时 15 毫秒
81.
María Teresa Orta Ledesma de Velásquez Ignacio Monje-Ramírez Sharon Velasquez-Orta Verónica Rodriguez-Muñiz Isaura Yáñez-Noguez 《臭氧:科学与工程》2017,39(4):264-272
The use of ozone has been investigated as a harvesting technique (ozone-flotation) for microalgae recovery from wastewater. This document summarizes the most outstanding results achieved to date by our working group, including the ozone effect on the lipid and fatty acid methyl ester (FAME) content. Additionally, the effect of the initial concentration of microalgal biomass on ozone-flotation was investigated using microalgae Scenedesmus sp. cultured in wastewater. Ozone-flotation required specific conditions to separate biomass from wastewater, depending on the type of microalgae strain, culture (single or mixed) and concentration. The effect of ozone-treatment improved lipid extractability and increased degree of FAME saturation. 相似文献
82.
Fluid bed drying and near infrared (NIR) spectroscopy are technologies widely used to dry and measure moisture content and other pharmaceutical granular materials’ attributes, respectively. This work focused on controlling a bench top fluid bed dryer using an industrial control system, the model predictive control (MPC) strategy, and NIR measurements of the moisture content of pharmaceutical powders. The MPC was implemented to reach the desired drying end-point while simultaneously manipulating two variables: airflow and inlet air temperature. These two manipulated variables were constrained based on the physical and chemical behavior of the process. The results showed that the use of the MPC with the inline NIR produced an adequate control performance and resulted at the same time in a reduction in energy consumption of as much as 60% in one case when compared with the current industrial practices. 相似文献
83.
The effect of buffer conditions -- varying in salt type, pH, and concentration -- on the separation of 8-aminonaphthalene-1,3,6-trisulfonic acid (ANTS)-labeled monosaccharides and complex-type carbohydrates was investigated. Different buffer systems for high and low electroosmotic flow conditions were chosen: a phosphate and a citrate background electrolyte, each at pH 2.5, a phosphate buffer, pH 9.0, and a borate buffer at pH 9.5. All buffer systems displayed differences in resolution and selectivity. Phosphate and borate buffer demonstrated the greatest selectivity changes for ANTS-labeled carbohydrates. While separation in the phosphate system relies mainly on differences in the charge-to-mass-ratio, additional selectivity can be achieved with borate complexation of glycoconjugates. The use of borate buffers improved monosaccharide separations whereas complex carbohydrates showed a loss in resolution. The citrate background electrolyte at low pH caused no significant changes in the separation performance. The pH 9.0 phosphate buffer showed a reversed migration order of the ANTS conjugates with a decreased resolution, compared to the pH 2.5 phosphate buffer, due to the strong electroosmotic flow generated under high pH conditions. An ovalbumin-derived oligosaccharide library demonstrates the significance of buffer selectivity for complex carbohydrate separations. The separation in the acidic phosphate and the alkaline borate buffer generates a different pattern and only the combination of both buffer systems allows an appropriate assessment of sample complexity. 相似文献
84.
Eduardo Díaz-Cedré Amado Cruz-Crespo Félix Ramos Morales Mauricio Tello Rico Joel Chaparro Gonzáles Manuel Rodríguez Pérez 《Welding International》2013,27(7):499-508
Welding with fusible electrode and shielding gas (GMAW) using a shielding mixture based on CO2 + O2 is a procedure with high potential for joining low-carbon and low-alloy steels compared with traditional mixtures based on argon. One of the reasons for this is related to the possibility of achieving a high penetration level without the need to increase the heat supply of the electric arc, by employing the shielding mixture of CO2 + O2, and the consequent decrease in the consumption of energy carriers. For that reason, the present paper presents a study on the influence of the shielding atmosphere characteristics (O2/CO2 ratio) and the welding current in the geometry of square groove weld joints on plates. For this purpose, a factorial experimental design was applied to obtaining regression equations, which would map such a behaviour. The equations were obtained using the O2/CO2 ratio and the welding current as independent variables. Nomograms were also plotted in order to make it easier to apply the results of this paper. 相似文献
85.
Abstract The major components of industrial thin (SSL) and thick (THSL) liquors from acidic magnesium–based sulphite pulping of Eucalyptus globulus wood have been characterized. The analysis of sugars in SSL revealed the predominance of xylose, which was present in the form of sugar monomer (ca. 70%) and as xylo-oligosaccharides (ca. 30%). Lignosulphonates (LS) were the most abundant organic fraction of spent liquor (ca. 50% of liquor dry matter) consisting of sulphonated oligomers (SO3H ≈ 20% w/w) of low molecular weight (Mw ≈ 1000–1300 Da) and constituted mainly by syringyl units (syringyl:guaiacyl ratio = 81:19). The major phenolic extractives of THSL were pyrogallol (93 g/ton) and gallic acid (1020 g/ton), and the most abundant fatty acid and sterol were tetracosanoic acid (6 g/ton) and β -sitosterol (45 g/ton), respectively. The structural changes of macromolecular components during the liquor evaporation were discussed. 相似文献
86.
87.
Bibiana García‐Soto Minia Sanjuás Jorge Barros‐Velázquez José R. Fuertes‐Gamundi Santiago P. Aubourg 《European Journal of Lipid Science and Technology》2011,113(4):487-496
This study provides a first approach concerning a novel chilling strategy, which employs a mixture of different preservative organic acids (ascorbic, citric and lactic) in the icing medium. Thus, ice prepared from water including two different concentrations of a commercial acid mixture‐formula (800 and 400 ppm; C‐800 and C‐400 conditions, respectively) were applied as icing system to three important commercial fish lean species (hake, Merluccius merluccius; megrim, Lepidorhombus whiffiagonis; angler, Lophius piscatorius). Lipid oxidation (peroxide value; thiobarbituric acid index; fluorescent compound formation) and hydrolysis (free fatty acid formation) were evaluated throughout the chilling time (up to 12–15 days) and compared to results obtained in fish kept under traditional ice prepared only from water (C‐0 condition); a complementary sensory evaluation was carried out. As a result of employing the C‐800 icing condition, a partial inhibition of lipid oxidation and hydrolysis development was obtained that was accompanied by a shelf life enhancement in all cases. Further research taking into account the complementary action of the present organic acids is envisaged. According to the lipid damage analysis, lipid hydrolysis was a more relevant event than lipid oxidation in all fish species tested. 相似文献
88.
We present results for the deposition of coatings of zirconium stabilized with Yttria (YSZ) and doped with aluminum and silver. The coatings were grown from an YSZ ceramic target symmetrically covered with metallic (Al, Ag) pieces on AISI 316L steel substrates, via the RF sputtering technique. The microstructure of the coatings was characterized by means of X-ray diffraction (XRD), the chemical composition was determined through X-ray dispersive energy (EDX) analysis, and the electrochemical response was evaluated via impedance (EIS) and Tafel corrosion techniques. The XRD analysis showed that the coatings exhibited peaks belonging to the target material, dopant elements, and oxides such as Al2O3. Electrochemical analysis indicated an increase in the corrosion resistance of the coatings grown on aluminum oxide. 相似文献
89.
Guillermo Osorio‐Revilla Tzayhri Gallardo‐Velázquez Arturo Ramírez‐Torres Yadira Rivera‐Espinoza 《加拿大化工杂志》2012,90(1):153-162
Residence time distributions (RTD) for aqueous maltodextrin solutions were determined in two kinds of spouted bed dryers: (1) conventional spouted bed (CSB) 0.305 m diameter with a bed of polypropylene beads and (2) spout‐fluid bed 0.143 m diameter with draft tube submerged in a bed of FEP® pellets (S‐FBDT). RTD, mean residence time tm, and spread of the distribution σ2, were determined at different drying temperatures, spouting velocities, bed depths, spraying pressures, and feed concentrations. Average values of tm and σ2 were 6.5 min and 26.6 min2 for the CSB and 6.9 min and 36 min2 for the S‐FBDT, respectively, for all operating conditions except spraying pressure. RTD curves were well represented by the response of an ideal stirred tank with a superimposed bypass of 15% on average for the CSB and 7% on average for the S‐FBDT dryer for all operating conditions. Increase in spraying pressure produced a reduction of tm and an increase in the bypass fraction of the product in both dryers. © 2011 Canadian Society for Chemical Engineering 相似文献
90.
Sulfuric acid treatment of ground tire rubber and its effect on the mechanical and thermal properties of polypropylene composites 下载免费PDF全文
Ernesto Hernández Hernández José Francisco Hernández Gámez Lorena Farías Cepeda Esthela Judith Chávez Muñoz Florentino Soriano Corral Silvia Guadalupe Solís Rosales Guadalupe Neira Velázquez Pablo González Morones Deidré I. Sánchez Martínez 《应用聚合物科学杂志》2017,134(21)
Ground tire rubber (GTR) was modified by sulfuric acid in order to improve its compatibility with and reinforcement of a polypropylene (PP) matrix. Polymer composites PP/GTR were prepared by melt mixing at different concentrations, with a maximum of 50 wt % of GTR. Studies by Fourier transform infrared spectroscopy (FTIR), surface specific area by BET (Brunauer, Emmett, and Teller), and scanning electron microscopy were used to characterize the untreated GTR and treated GTR, while the mechanical and thermal properties of the PP/GTR composites were assessed to understand how the surface treatment of GTR affected the mechanical and thermal properties of the composite PP/GTR. FTIR revealed the presence of sulfonic groups on the surface of sulfuric acid–treated GTR, and BET analyses showed an increase of about 625% in the specific surface area as a result of the high porosity produced by the treatment. In all composites containing treated GTR, a higher Young's modulus was obtained than for composites containing untreated GTR. Particularly, an increase of about 275% in the Young's modulus was obtained in composites with treated GTR (40 wt %) against that containing untreated GTR. However, a more significant reduction of the elongation at break was observed in composites containing treated GTR than in those containing untreated GTR. Also, an increase of the crystallization temperature of PP as a function of GTR was observed by differential scanning calorimetry, but the crystallinity of the composites was reduced by the addition of both untreated and treated GTR. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44858. 相似文献