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排序方式: 共有1747条查询结果,搜索用时 14 毫秒
191.
LAURA A. IBÁÑEZ-CASTILLO JESÚS CHÁVEZ-MORALES MIGUEL A. MARIÑO 《Water Resources Management》1997,11(3):165-184
A methodology is presented for planning the operation of the Fuerte-Carrizo irrigation system in northwest Mexico. The system has two storage dams, two irrigation districts, and water transfer capabilities between both dams. The methodology uses a combination of linear programming (LP) and simulation. The LP model maximizes the net return of the farmers, subject to restrictions of the system, availability of water and land, and water transfer relationships. The simulation model is programmed as a microcomputer interactive package simulating the performance of the system. The methodology has proven to be a useful tool to assist those responsible for the operation of the irrigation system. 相似文献
192.
J. Álvarez-Rodríguez A. Guerrero-Ruiz A. Arcoya I. Rodríguez-Ramos 《Catalysis Letters》2009,129(3-4):376-382
The effect of thiophene (Th) addition, in the concentration range 0–6 ppm, on the performance of Ru/KL catalysts is analyzed for the liquid phase hydrogenation of citral at 323 K and 4 MPa. The results show a promoter effect of thiophene on the overall hydrogenation activity of the catalysts, with a maximum at 3 ppm concentration of Th. Particularly, it is evidenced an increase in the selectivity towards the hydrogenation of the carbonyl group of citral. 相似文献
193.
Miguel Ángel Rincón‐Cervera María Dolores Suárez‐Medina José Luis Guil‐Guerrero 《European Journal of Lipid Science and Technology》2009,111(9):920-925
Fifteen roes from different marine fish species available in Spain were analyzed in order to determine their fatty acid (FA) composition, especially the eicosapentaenoic acid (20:5n‐3, EPA) and docosahexaenoic acid (22:6n‐3, DHA) contents. Roes from Atlantic bonito (Sarda sarda), European squid (Loligo vulgaris), cuttlefish (Sepia spp.), lumpfish (Cyclopterus lumpus), European hake (Merluccius merluccius), Atlantic salmon (Salmo salar) and gonads of male Atlantic mackerel (Scomber scombrus) reached EPA + DHA amounts higher than 30% of the total FA, and among them, roes from lumpfish, European hake and salmon provide different FA type ratios that could make them adequate as dietary sources of EPA and DHA. 相似文献
194.
J. L. Ortega-Vinuesa M. J. Gálvez-Ruiz R. Hidalgo-Álvarez 《Journal of materials science. Materials in medicine》1995,6(12):754-761
The study of the behaviour of biointerfaces is of great interest because it enables us to gain a much better understanding of the interactions between different biological compounds. Superficial processes are strongly dependent on such interactions. In the present work, we have focused our attention on the adsorption of a cationic lipid onto different colloidal polymer systems. Subsequently, the coadsorption of this lipid and an immunoprotein (F(ab')
2) was performed trying to achieve stable latex particles. The aim was to obtain a structured interface similar to that of a simple biological membrane. Mainly, we have placed emphasis on the study of interaction forces that govern lipid adsorption when we change the dielectric constant in the medium. In order to obtain homogeneous aqueous lipid solutions some ethanol was added to samples. The adsorption isotherms were carried out at different experimental conditions, changing the ethanol contents and the pH of the environment. Moreover, the electrokinetic behaviour and the colloidal stability of these biocomplexes were studied, and both yielded highly compatible results. The adsorption of lipid onto polymeric sorbents is an irreversible process that takes place rapidly. The preferential interaction between the lipid and polymeric surfaces is electrostatic. Only in those samples with low alcohol concentration, hydrophobic forces take place weakly. Lipid-surface interactions are influenced by the nature of buffer ions. The colloidal stability of the systems decreases as the amount of the adsorbed lipid is higher. Sequential coadsorption experiments showed that the lipid molecules adhere both to the polymer surface and to the previously adsorbed immunoprotein. 相似文献
195.
Alicia López María Ángeles Losada Ignacio Garcés Ignacio de Miguel 《Photonic Network Communications》2006,11(1):111-121
We present a novel CWDM metropolitan multiple-access ring network based on optical switching of packets according to their
wavelength. Each node within the MAN is identified by a combination of wavelength and numerical address. Hence, nodes are
able to drop packets presenting a particular wavelength and numerical address, but can insert packets in any wavelength into
the ring. This configuration allows wavelength sharing, as several nodes are identified by the same wavelength (but different
numerical addresses), and simplifies switching requirements since the set of numerical addresses is reduced. We analyze the
viability and scalability of such a network, determining the number of nodes supported by the network under different traffic
scenarios and wavelength resources. The impact of switching time on network performance is also analyzed in order to determine
which switching technology should be employed when implementing the network.
An erratum to this article is available at . 相似文献
196.
lvaro Beltrn Eleuterio lvarez M. Mar Díaz‐Requejo Pedro J. Prez 《Advanced Synthesis \u0026amp; Catalysis》2015,357(13):2821-2826
The reaction of aldehydes, amines and alcohols usually leads to a series of equilibria from which isolation of one product is difficult to achieve. We have found that this three‐component reaction can be controlled and directed in an exclusive manner toward the formation of the hemiaminal ether. A series of 33 hemiaminal ethers has been obtained in high yields, from different aldehydes, amines and alcohols, under very mild conditions just with molecular sieves as promoter.
197.
198.
IPTV broadcast channels and video content distribution are increasingly saturating network paths. New solutions based on inter‐domain multicast protocols could contribute to the enhancement of multimedia content distribution over the Internet. The aim of this paper is to propose new capabilities for an existing inter‐domain multicast protocol, the Protocol Independent Multicast‐Sparse Mode. We describe the modified protocol and analyze its behavior using newly developed tools based on an open‐source software simulator. The resulting protocol does not require topology information, which is advantageous for easier deployment. In addition, the adopted solution avoids inherent problems with inter‐domain multicast routing, such as multiple paths and path asymmetries. 相似文献
199.
Clara Guglieri Eva Céspedes Ana Espinosa María Ángeles Laguna‐Marco Noemi Carmona Yukiharu Takeda Tetsuo Okane Tetsuya Nakamura Mar García‐Hernández Miguel Ángel García Jesús Chaboy 《Advanced functional materials》2014,24(14):2094-2100
Discoveries of room‐temperature ferromagnetism (RTFM) in semiconductors hold great promise in future spintronics technologies. Unfortunately, this ferromagnetism remains poorly understood and the debate concerning the nature, carrier‐mediated versus defect‐mediated, of this ferromagnetism in semiconducting oxides is still open. Here, by using X‐ray absorption (XAS) and X‐ray magnetic circular dichroism (XMCD), it is demonstrated that the oxygen ions have a ferromagnetic response in different ZnO‐based compounds showing RTFM behavior: ZnO nanoparticles capped with organic molecules and ZnO/ZnS heterostructures. These results demonstrate the intrinsic occurrence of RTFM in these systems, and point out that it is not related to the metallic cation but it relays on the conduction band of the semiconductor. 相似文献
200.
Gudjónsdóttir M Jónsson Á Bergsson AB Arason S Rustad T 《Journal of food science》2011,76(4):E357-E367
The effect of using polyphosphates during prebrining and the effect of prebrining time of cold water shrimp (Pandalus borealis) was studied with low field nuclear magnetic resonance (LF-NMR) transverse relaxation time measurements (benchtop and unilateral) and near infrared (NIR) spectroscopy with the aim of improving shrimp processing. Strong calibrations were obtained for moisture content and water-holding capacity (WHC) using the NIR technique. Multivariate analysis indicated significant correlations between benchtop NMR parameters and moisture content and WHC, as measured with physicochemical methods and NIR spectroscopy. Significant correlations were also observed between NMR parameters and muscle pH, protein content, and phosphate content. The study showed that LF-NMR contribute to improved understanding of the shrimp brining process and to improved process control on-line or at-line, especially in combination with NIR measurements. However, optimization of the unilateral device is necessary. 相似文献