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131.
Nizar Bel Hadj Ali Mohamed Sellami Anne-Françoise Cutting-Decelle Jean-Claude Mangin 《Engineering Structures》2009,31(11):2766-2778
The response of a steel structure is closely related to the behavior of its joints. This means that it is necessary to take explicit account of joint properties in order to ensure a consistent approach to design optimization of steel frames. Semi-rigid design has been introduced into steel construction standards such as Eurocode 3 and AISC. However, in the absence of appropriate guidelines, engineers encounter difficulties when bringing in semi-rigid design to everyday engineering practice. Moreover, connection design significantly affects the production cost of steel frame structures. Thus, a realistic optimization of frame design should take into account the effective costs of different stages of production including manufacturing and erection activities. This paper presents a Genetic Algorithm based method for multi-stage cost optimization of steel structures. In the objective function, the total cost of different production stages is minimized. A new cost model is presented that itemizes costs of all stages of production (material supply, manufacturing, erection and foundation). Design examples are used to validate the proposed methodology. Numerical validation shows that the multi-stage design optimization results in substantial cost benefits between 10% and 25% compared to traditional design of steel frames. Furthermore, the developed methodology is shown to be capable of measuring the possible impact of design choices in the early design stage thus assisting designers to make better design decisions. 相似文献
132.
The diversity and dynamics of the dominant microbial communities arising during the manufacture and ripening of four batches of naturally fermented Cabrales cheese were investigated by the PCR-DGGE culture-independent technique. Total microbial DNA was extracted from cheese milk, curd and cheese samples and used as template material in PCR experiments to amplify the V3 region of the bacterial 16S rRNA gene, plus the D1 region of the eukaryotic 26S rRNA gene. These regions were then analysed using DGGE. Eukaryotic and bacterial bands were identified by isolation, reamplification and sequencing. The results were compared to those obtained in a previous microbial characterization of the same four batches using classical culturing methods. Great variability was recorded between batches by the PCR-DGGE technique. This was also shown by culturing, and underlines the uniqueness of artisanal products. Lactocococcus lactis subsp. lactis was dominant from the cheese milk stage until the end of ripening, whereas populations of certain Lactobacillus species appeared during ripening. Populations of species never isolated by culturing were found to be numerous by the PCR-DGGE method, in particular Lactococcus garvieae and Lactococcus raffinolactis. Other, completely unknown lactococci were also detected. The dominant eukaryotic populations from day 15 onwards were those of Penicillium roqueforti and Geotrichum candidum. 相似文献
133.
Ana Ortega-Regules José María Ros-García Ana Belén Bautista-Ortín José María López-Roca Encarna Gómez-Plaza 《European Food Research and Technology》2008,227(1):223-231
The morphology and composition of skin and pulp cell walls of four premium red wine grape (Vitis vinifera L.) varieties were studied to determine whether the technological differences observed in previous studies between the four
different varieties during the winemaking process (especially, the anthocyanin extractability) could be partly explained by
their respective cell wall compositions. Monastrell grapes showed the highest amount of cell wall material in their skins
(55–57 mg cell wall/g skin), while Syrah showed the largest amount of cell wall material in the pulp (5.1 mg cell wall/g pulp).
The highest percentage of galactose and cellulosic glucose in skin and pulp cell walls was also found in Monastrell grapes.
The cell wall composition of Monastrell grapes, together with their morphology, suggests that the firmer pulp and skin are
responsible for the difficulties this variety shows for anthocyanin extraction (extractability index varying from 37 to 60).
As cell wall composition may be modulated by the action of enzymes, the activity of pectinmethylesterase, polygalacturonase,
cellulase and α- and β-galactosidase was studied. No polygalacturonase and cellulase activity was found. The two galactosidases
showed higher activity than pectinmethylesterase (25–290 units/g tissue versus 0.3–0.4 units/g tissue), especially in Cabernet
Sauvignon grapes, although in Monastrell grapes α- and β-galactosidase activity was low, which may explain the large amount
of galactose in Monastrell grapes cell wall. 相似文献
134.
Ana Belščak Draženka Komes Dunja Horžić Karin Kovačević Ganić Damir Karlović 《Food research international (Ottawa, Ont.)》2009,42(5-6):707-716
Recent trends in food marketing suggest that cocoa products, besides being favourite sweets among consumers, also present multiple-benefit foodstuffs, which are becoming objects of increased scientific research, mainly because of their interesting phytochemical composition. UV/VIS spectrophotometric and high-performance liquid chromatography (HPLC-PDA) methods were applied in order to compare the composition of polyphenols and methylxanthines in commercial cocoa products affected by different extraction solvents. Antioxidant capacity of water and methanol extracts was evaluated using DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) and FRAP (ferric reducing/antioxidant power) assays. The obtained results confirmed that the content of polyphenols and methylxanthines, as well as the antioxidant capacity of cocoa products depend on the content of their cocoa solids. Among the tested cocoa products, the highest content of bioactive compounds (polyphenols and methylxanthines) was determined in extracts of cocoa products with the highest content of cocoa solids (cocoa liquor, cocoa powder and dark chocolate with 88% cocoa solids), while the lowest content was determined in milk chocolate and cocoa bar extracts. The most abundant phenolic compound in cocoa extracts was (?)-epicatechin, while the most abundant methylxanthine was theobromine. In comparison with water, 70% methanol demonstrated higher efficiency for the extraction of the studied bioactive compounds from cocoa products. 相似文献
135.
136.
Silver halide sensitized gelatin (SHSG) is one of the most interesting techniques for the production of holographic optical elements, achieving relatively high sensitivity of photographic material with a low scattering of dichromated gelatin. Here we present experimental results for SHSG derived from the novel BB-640, a red-sensitive ultra-fine-grain emulsion from Holographic Recording Technologies (Steinau, Germany). The material is characterized before recording and after processing, and information about the thickness, absorption, and refractive-index modulation of the final holograms is obtained. The influence of the developer is analyzed, and diffraction efficiencies as great as 96.2% (after allowing for reflections) with a transmission of 1% and absorption and scatter losses of 2.8% are obtained with AAC developer. Our investigations reveal that high-quality SHSG transmission holograms may be obtained with the new BB-640 plates. 相似文献
137.
Politova E. D. Kaleva G. M. Bel’kova D. A. Mosunov A. V. Sadovskaya N. V. Kiselev D. A. Il’ina T. S. Shvartsman V. V. 《Inorganic Materials》2021,57(9):942-949
Inorganic Materials - We have studied the crystal structure and dielectric and local piezoelectric properties of (Na0.5Bi0.5)(Ti1–xMnx)O3 (x = 0–0.1) modified sodium bismuth... 相似文献
138.
Theoretical and experimental study of the bleaching of a dye in a film-polymerization process 总被引:2,自引:0,他引:2
The quantum efficiency and the molar-absorption coefficients of different phenothiazine dyes are obtained by means of fitting the experimental data of transmittance as a function of time. An analytical expression for the intensity transmitted in a photopolymerizable holographic material is obtained, and good agreement between theory and experience is also achieved. The analysis of these parameters is of fundamental quantities in the photochemical characterization of holographic recording materials. 相似文献
139.
140.
A method for recording of holograms on spherical substrates is presented. As recording material we used a photopolymer placed between two spherical glass plates that are concentric. 相似文献