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21.
Bill Vassiliadis Antonia Stefani John Tsaknakis Athanassios Tsakalidis 《Telematics and Informatics》2006,23(4):271-293
IT outsourcing is not a new concept. Originating from the early 60’s in the form of time sharing, IT outsourcing has evolved to the application service provision (ASP) model, in the late 90’s to pure services in the beginning of the century. Services, and their major representative web services, are actually the next phase of the movement toward Internet-based componentized software, known in the not so distant past as ASP. As the continuous expansion of the Internet and its relating technologies creates new marketing opportunities, traditional monolithic architectures are giving way to service-oriented computing (SOC), the architecture that enables service provision. SOC permits the utilization of large systems which are comprised of self-containing building blocks: services. Services may be made public, searched, reused and combined to form complex business processes while in the same time retaining a significant level of flexibility. Services and SOC have emerged as a response to a fundamental shift in enterprise business culture that started at the late 90’s. Although they are promising as an IT outsourcing enabler, many issues need to be dealt with before they can be considered suitable for wide adoption. These issues are of technological, business, economic and cultural nature and they were also faced by ASPs in the past. It is worth revisiting the successes and failures of the ASP model in order to get a better understanding of the evolving IT outsourcing industry. In this work, we describe the evolution of service provision from its initial form as software application, through the application service provision era and towards the new trend of web services. 相似文献
22.
Balbino García-Criado Antonia García-Ciudad M Esther Prez-Corona 《Journal of the science of food and agriculture》1991,57(4):507-515
Near infrared reflectance spectroscopy (NIRS) was evaluated as a method to predict the botanical composition of seminatural grassland in ‘dehesa’ systems. Samples of herbaceous biomass were harvested over four consecutive years, determining in each—by manual separation—the proportion by weight of the following taxonomic groups: grasses, legumes and the rest of the families in a single block (‘others’). After reconstructing the natural samples they were analysed by NIRS. One set of samples (calibration set) was selected for the development of the equations, assaying different mathematical treatments (log l/R, first derivative and second derivative). The ranges of coefficients of multiple determination and standard errors of calibration, respectively, for the various components were: grasses, 0.86 to 0.92 and 6.66 to 9.14; legumes, 0.77 to 0.81 and 6.82 to 7.43; and ‘others’, 0.85 to 0.88 and 8.17 to 9.54. The remaining samples not included in the development of the NIRS equations (prediction set) were used for the purposes of validating the best equations. Standard errors of performance were: grasses, 6.12; legumes, 7.56 and ‘others’, 7.70. 相似文献
23.
We propose to study the scattering properties of dense distributions of spherical scatterers by resorting to an iterative solution of the Foldy-Twersky equation for the propagation of the coherent field. As a result of the first step of the iterative procedure, the host medium is substituted by an effective medium of complex refractive index to account for the multiple-scattering processes that occur among the particles. Although we truncate the above-mentioned iterative procedure to the second step, the results of our calculations are in excellent agreement with previous experimental results of Zaccanti et al. ("Measurement of optical properties of high-density media," to be published in Applied Optics) for the scattering coefficient of Intralipid solutions up to a volume density of 15% and show a limited disagreement at a volume density of 22%. 相似文献
24.
José M. Contreras Antonia Jiménez-Morales José M. Torralba 《Journal of Materials Processing Technology》2009,209(15-16):5618-5625
The aim of this work is to fabricate bronze components by metal injection moulding (MIM) studying the possibility of changing partially or totally the gas atomised powder by water atomised ones that are cheaper than the former. In order to carry out this study, a bronze 90/10 gas atomised spherical powder (usual MIM powder <22 μm) and two water atomised irregular powders (particle size <35 μm and <140 μm) were mixed in different proportions. As received powders and their mixtures were used to fabricate feedstocks and processed by MIM to evaluate the influence of powder particle size and morphology on debinding and sintering stages. Finally, both mechanical properties hardness and maximum flexural stress were determined to characterize the sintered materials. The addition of irregular fine and coarse powders was found to affect the moulding process, although densities and mechanical properties close to values of gas atomised one were obtained after sintering. Therefore, the use of water atomised bronze powders could be a promising way to diminish production costs in this technology. 相似文献
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26.
Francisco J Hernández‐Fernández Antonia P de los Ríos Manuel Rubio Demetrio Gómez Gloria Víllora 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2007,82(10):882-887
BACKGROUND: Seven ionic liquids (ILs) based on 1-alkyl-3-methylimidazolium cation in combination with hexafluorophosphate and bis{(trifluoromethyl)sulfonyl}imide anions were tested as reaction media for lipase-catalyzed transesterification in low water conditions. With the aim of improving the activity and/or selectivity of the lipase, various treatments were applied to ionic liquid media such as equilibration with aqueous solutions of salts, NaHCO3 or Na2CO3, or the addition of a catalytic amount of a non-reactive organic base to the reaction mixture, triethylamine. RESULTS: The treated ionic liquids were shown to be excellent media for lipase-catalyzed ester synthesis by transesterification compared with conventional organic solvents, such as n-hexane. All treatments were found to enhance the synthetic activity of the enzyme, the best results being achieved with the addition of triethylamine. The addition of a catalytic amount of this base to the ILs resulted in a significant increase in both the synthetic activity and selectivity values. For instance, the synthetic activity in [emim+][TfN2−] was enhanced more than 12 times and the selectivity increased from 86% to 95% when triethylamine was used. CONCLUSION: These treatments could be easy-to-use approaches to improve the efficiency of enzymatic reactions in ionic liquids when the reaction does not proceed smoothly. Copyright © 2007 Society of Chemical Industry 相似文献
27.
Antonia P. de los Ríos Francisco J. Hernández-Fernández Demetrio Gómez 《Desalination》2010,250(1):101-14
We previously reported the selective simultaneous separation of the substrates and products of a transesterification reaction (vinyl butyrate, 1-butanol, butyl butyrate and butyric acid) through supported liquid membranes (SLMs) based on 1-n-alkyl-3-methylimidazolium cations combined with tetrafluoroborate, hexafluorophosphate and bis{(trifluoromethyl)sulfonyl}imide anions. The best results were obtained by the use of tetrafluoroborate based ionic liquids, which led us to further investigate the use of these new supported liquid membranes for the selective separation of different substrates and products of transesterification reactions. With this aim, the permeability of sixteen different organic compounds (vinyl esters, aliphatic esters, alcohols and carboxylic acids) through SLMs containing tetrafluoroborate based ionic liquids ([bmim+][BF4−] and [omim+][BF4−]) were evaluated. It was found that permeability increased as the alkyl chain length decreased for the same organic functional group. In addition, significant permeability differences were found between the different organic functional groups.As regards the operational stability of these SLMs, they were seen to be very stable when tested over eight continuous cycles of 48 h each. 相似文献
28.
Composition of plant cell walls 总被引:1,自引:0,他引:1
29.
30.
Ferrante MC Cirillo T Naso B Clausi MT Lucisano A Cocchieri RA 《Journal of food protection》2007,70(3):706-715
Seven target polychlorinated biphenyls (PCBs; IUPAC nos. 28, 52, 101, 118, 138, 153, and 180) and the organochlorine pesticides (OCPs) hexachlorobenzene (HCB) and dichlorodiphenyltrichloroethane (DDT) and its related metabolites (p,p'-DDT, p,p'-DDE, and p,p'-DDD) were quantified in edible tissues from seven marine species (European hake, red mullet, blue whiting, Atlantic mackerel, blue and red shrimp, European flying squid, and Mediterranean mussel) from the Gulf of Naples in the southern Tyrrhenian Sea (Italy). PCBs 118, 138, and 153 were the dominant congeners in all the species examined. The concentrations of all PCBs (from not detectable to 15,427 ng g(-1) fat weight) exceeded those of all the DDTs (from not detectable to 1,769 ng g(-1) fat weight) and HCB (not detectable to 150.60 ng g(-1) fat weight) in the samples analyzed. The OCP concentrations were below the maximum residue limits established for fish and aquatic products by the Decreto Ministerale 13 May 2005 in all the samples analyzed; therefore the OCPs in the southern Tyrrhenian Sea species are unlikely to be a significant health hazard. Conversely, the mean concentrations of PCBs exceeded (greatly in some cases) the current limits (200 ng(-1) fat weight) set by the European Union for terrestrial foods. Although the manufacture and use of PCBs are banned or highly restricted, these compounds still are important persistent chemical contaminants in the Gulf of Naples. 相似文献