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111.
Galo R. Urrea‐García Sergio Reséndiz‐Camacho José Álvarez‐Ramírez Guadalupe Luna‐Solano 《化学工程与技术》2015,38(3):521-529
The application of a variable control structure for tubular reactors, based on multiple temperature measurements, is explored. The proposed structure allows the controller to adapt to temperature error variations along the tubular reactor. Controllers can be designed from simple input‐output first‐order dynamical models obtained from step responses and are coupled with a dynamic law for assigning a variable weight to conventional feedback cascade control loops. The simulation results show that the variable structure based on linear proportional‐integral controllers enhances the performance and robustness properties of conventional cascade schemes for controlling the outlet reactor concentration. Major advantages are shown in the face of a variety of concentration and temperature feed disturbances. 相似文献
112.
The impact of linamarin and lotaustralin content in the leaves of lima beans, Phaseolus lunatus L., on the second and third trophic levels was studied in the two-spotted spider mite, Tetranychus urticae (Koch), and its predator Phytoseiulus persimilis Athias-Henriot. The content of linamarin was higher in terminal trifoliate leaves (435.5 ppm) than in primary leaves (142.1 ppm)
of Henderson bush lima beans. However, linamarin concentrations were reversed at the second trophic level showing higher concentrations
in spider mites feeding on primary leaves (429.8 ppm) than those feeding on terminal trifoliate leaves (298.2 ppm). Concentrations
of linamarin in the predatory mites were 18.4 and 71.9 ppm when feeding on spider mites grown on primary and terminal leaves,
respectively. The concentration of lotaustralin in primary lima bean leaves was 103.12 ppm, and in spider mites feeding on
these leaves was 175.0 ppm. Lotaustralin was absent in lima bean terminal trifoliate leaves and in mites feeding on these
leaves. Fecundity of spider mites feeding on lima bean leaves (primary or trifoliate) was not significantly different from
mites feeding on red bean, Phaseolus vulgaris L., primary leaves. However, the progeny sex ratio (in females per male) of spider mites feeding on lima bean leaves was
significantly lower than progeny of spider mites feeding on red bean leaves (control). Fecundity and progeny sex ratio of
P. persimilis were both significantly affected by the concentration of linamarin present in the prey. Changes in concentration of linamarin
in living tissue across the three trophic levels are discussed. 相似文献
113.
S.?Amalia?PooleyEmail author Bernabé?L.?Rivas Amitza?L.?Cárcamo Guadalupe?del?C. Pizarro 《Polymer Bulletin》2009,62(4):469-485
A novel series of copolymer hydrogels of 2-(dimethylamino)ethylacrylate (DMAEA)/2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) were prepared by solution free radical polymerization at different feed monomer mol ratios. The monomer reactivity ratios were determined by Kelen–Tüdös method. According to that, the monomer reactivity ratios for poly(DMAEA-co-AMPS) were r1 = 0.125 and r2 = 2.85, (r1 × r2 = 0.356). The effect of reaction parameters, including the concentration of cross-linking reagent N,N′-methylene-bis-acrylamide (MBA) and initiator ammonium persulfate (APS), the monomer concentration, pH, temperature, salt solutions, and solvent polarity on the water absorption have been also studied. The hydrogels achieved water-absorption values of 430 g of water/g of xerogel for the copolymer 1:2 richest in AMPS moiety. This copolymer is also very stable to the temperature effect. The optimum pH for the copolymers is 7. Aqueous solutions of the copolymers showed lower critical solution temperature behaviour (LCST). The phase transition temperatures of aqueous solutions of these copolymer increased with increasing of hydrophilic AMPS unit content in the copolymers. The glass transition temperature (Tg) of hydrogels showed a decrease by increasing of comonomer DMAEA content. 相似文献
114.
Marciano-Melchor M Navarro-Morales E Román-Hernández E Santiago-Santiago JG Silva-Ortigoza G Silva-Ortigoza R Suárez-Xique R 《Journal of the Optical Society of America. A, Optics, image science, and vision》2012,29(6):1035-1046
The aim of this paper is to obtain expressions for the k-function, the wavefront train, and the caustic associated with the light rays refracted by an arbitrary smooth surface after being emitted by a point light source located at an arbitrary position in a three-dimensional homogeneous optical medium. The general results are applied to a parabolic refracting surface. For this case, we find that when the point light source is off the optical axis, the caustic locally has singularities of the hyperbolic umbilic type, while the refracted wavefront, at the caustic region, locally has singularities of the cusp ridge and swallowtail types. 相似文献
115.
José de Jesús Ornelas-Paz J. Manuel Martínez-Burrola Saúl Ruiz-Cruz Víctor Santana-Rodríguez Vrani Ibarra-Junquera Guadalupe I. Olivas J. David Pérez-Martínez 《Food chemistry》2010
Raw and cooked (boiled and grilled) Poblano, Bell, Chilaca, Caribe, Jalapeño, Serrano, Habanero, and Manzano peppers were evaluated for tristimulus colour, capsaicinoids (capsaicin, dihydrocapsaicin, nordihydrocapscapsaicin), and total phenolic contents. Boiling (96 °C) and grilling (210 °C) was performed under household conditions according to typical procedures of the Mexican cuisine. Contents of capsaicin (0.6–913.8 μg/g), dihydrocapsaicin (0–756.9 μg/g), nordihydrocapsaicin (0–68.2 μg/g), and total phenolics (1150.5–2190.0 μg of gallic acid equivalents/g) in raw peppers varied widely between types of peppers. Moderate losses (1.1–28.1%) in capsaicinoids were induced by boiling while grilling caused a significant increase (2.6–924.9%) in the content of these compounds. Proportion of individual capsaicinoids was similar in raw and cooked peppers. Boiling and grilling sequentially increased (7.4–137.0%) the total phenolic content in pungent peppers. Total phenolic content in non-pungent Bell peppers was reduced by cooking (1.6–26.9%). Boiling induced smaller changes in colour values (L*, a*, and b*) compared to grilling. The results demonstrated that Mexican raw peppers are rich in capsaicinoids and phenolic compounds. Household cooking can cause either decreases or increases in the content of such compounds in peppers. 相似文献
116.
Andra C. Bertolini Luis A. Bello‐Prez Guadalupe Mndez‐Montealvo Claudia A. S. Almeida Franco Lajolo 《Starch - St?rke》2010,62(6):277-284
Unripe banana flour can be an alternative to minimize post‐harvest loss and to increase the aggregate value of banana fruit. Flour from unripe banana is rich in phytosterols and resistant starch, being proposed as health food. Flours from unripe banana peel and pulp were evaluated on their composition, phytosterols content, thermal and rheological properties, and pasting profiles. High amounts of β‐sitosterol, campesterol, and stigmasterol were found in flour from banana peel. These samples showed lower viscosity values of pasting profiles, lower energy enthalpy on gelatinization, and higher temperature of gelatinization than those ones from pulp. Anti‐oxidant treatment of fruits with citric acid does not change pasting profiles of flours from pulp, but resulted in slight increase in viscosity, suggesting that structure of starch could be modified by acidification. 相似文献
117.
Relationships between Chemical Composition and Quality‐Related Characteristics in Bread Making with Wheat Flour–Fine Bran Blends
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118.
119.
Alba María Guadalupe Orellana González Rodrigo Máximo Sánchez-Román Marcos Vinicius Folegatti Cornélio Alberto Zolin 《Water Resources Management》2011,25(13):3371-3386
A dynamic systems simulation model of water resources was developed as a tool to help analyze alternatives to water resources
management for the Piracicaba, Capivari and Jundiaí River Water Basins (RB-PCJ), and used to run six 50-year simulations from
2004 to 2054. The model estimates water supply and demand, as well as contamination load by several consumers. Six runs were
performed using a constant mean precipitation value, changing water supply and demand and different volumes diverted from
RB-PCJ to RB-Alto Tietê. For the Business as Usual scenario, the Sustainability Index went from 0.44 in 2004 to 0.20 by 2054.
The Water Sustainability Index changed from 74% in 2004 to 131% by 2054. The Falkenmark Index changed from 1,403 m3 person − 1 year − 1 in 2004 to 734 m3 person − 1 year − 1 by 2054. We concluded that sanitation is one of the major problems for the PCJ River Basins. 相似文献
120.
Regulation of passive outputs of nonlinear systems can be easily achieved with an integral control (IC). In many applications, however, the signal of interest is not a passive output and ensuring its regulation remains an open problem. Also, IC of passive systems rejects constant input disturbances, but no similar property can be ensured if the disturbance is not matched. In this paper we address the aforementioned problems and propose a procedure to design robust ICs for port-Hamiltonian models, that characterize the behavior of a large class of physical systems. Necessary and sufficient conditions for the solvability of the problem, in terms of some rank and controllability properties of the linearized system, are provided. For a class of fully actuated mechanical systems, a globally asymptotically stabilizing solution is given. Simulations of the classical pendulum system illustrate the good performance of the scheme. 相似文献