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11.
Radiation absorption and rate constants for carbaryl photocatalytic degradation in a solar collector 总被引:1,自引:0,他引:1
Camilo A. Arancibia-Bulnes Erick R. Bandala Claudio A. Estrada 《Catalysis Today》2002,76(2-4):149-159
We discuss an analytical model for the evaluation of radiation absorption in a tubular photocatalytic reactor. The model has no adjustable parameters and takes into account scattering in all directions. We compare the results of this model with those of Monte Carlo (MC) simulations and of a Lambert–Beer (LB) approximation, for a reactor illuminated by a parabolic solar concentrator. A good correspondence is found with the MC simulations. In particular, the model displays the correct saturation behavior of absorption for large catalyst particle concentrations, which is not obtained with the LB approximation. We have carried out experiments for the degradation of carbaryl in a solar parabolic collector (PC). The model is used to calculate the rate constant for this degradation from the experimental data. The theoretical model predictions reproduce well, the trends observed in the experiments. 相似文献
12.
A. N. Spector Lay James Gibson Ashok K. Dutt William F. Hyde Paul B. Sherman Hans-Jurg Buttler Bernard Malamud Robert N. Anderson M. Penouil R. W. Keyes Lee R. McPheters William R. Eadington Kurt Puchinger Arthur E. Kartman Charles E. Starnes J. Barry Riddell Erick Sheppard Leon E. Zonn Craig Moore Neil S. Grigg K. Shimizu Daniel A. Griffith Noel D. Uri Micheal Ross Jack E. Adams Robert G. Fletcher Karol J. Krotki Peter D. Beaulieu Fred E. Case W. Edwin Derrick Barry D. Solomon Debnath Mookherjee John E. Keith Yuk Lee Andrew A. Dzurik W. W. Hall Jr. Lloyd W. Klemke Ted J. Adamczyk 《The Annals of Regional Science》1981,15(3):82-146
13.
Outlined here is a method for applying a model of discharge flow through a series of sharp-edged orifices from an inlet plenum, to accurately predict the total pressure drop across the flow distribution geometry. This particular case relates to a cross-flow filtration membrane module, but is applicable for any flow distribution system of a similar format. 相似文献
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This work is the second part of an overall project, the aim of which is the development of general mix design rules for concrete containing different kinds of mineral admixtures. The first part presented the separation of the different physical effects responsible for changes in cement hydration when chemically inert quartz powders are used in mortars. This second part describes the development of an empirical model, based on semiadiabatic calorimetry measurements, which leads to the quantification of the enhancement of cement hydration due to the heterogeneous nucleation effect at short hydration times. Experimental results show that not all the admixture particles participate in the heterogeneous nucleation process. Consequently, the concept of efficient surface Seff is introduced in the model. Seff is the total admixture surface S (m2 of mineral admixture/kg of cement) weighted by a function ξ(p). The efficiency function ξ(p) depends only on the replacement rate p and is independent of time, fineness and type of mineral admixture used. It decreases from 1 to 0: Low replacement rates give an efficiency value near 1, which means that all admixture particles enhance the hydration process. An efficiency value near 0 is obtained for high replacement rates, which indicates that, from the hydration point of view, an excess of inert powder does not lead to an increase in the amount of hydrates compared with the reference mortar without mineral admixture. The empirical model, which is mainly related to the specific surface area of the admixtures, quantifies the variation of the degree of hydration induced by the use of inert mineral admixtures. One application of the model, coupled with Powers' law, is the prediction of the short-term compressive strength of mortars. 相似文献
16.
This work is the third part of an overall project the aim of which is the development of general mix design rules for concrete containing different kinds of mineral admixtures (also named mineral additions or mineral constituents). It deals with the compressive strength of mortars made with up to 75% of crushed quartz, limestone filler or fly ash of different fineness. The paper presents all the experimental results as a sort of database and emphasizes the effects on strength of the nature, amount and fineness of mineral admixtures. For short hydration times (1 to 2 days), the nature of mineral admixture is not a significant parameter, as mortars containing the same amount of different kinds of admixtures having equivalent fineness present similar strengths. For long hydration times (up to 6 months), the excess strength due to fly ash pozzolanic activity is quantified by the difference between the strengths of mortars containing the same proportions of inert and pozzolanic admixtures with the same fineness. In the case of inert mineral admixtures, the increase in strength with the fineness of mineral admixtures cannot be explained by the filler effect, but can be attributed to the physical effect of heterogeneous nucleation. In the next part of this work, these results will be used for the elaboration of an empirical model leading to the quantification of both physical and chemical effects. This model presents strong similarities with the previous model based on calorimetric results. 相似文献
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Erick García-Benitez Stephen Yurkovich Kevin M. Passino 《Journal of Intelligent and Robotic Systems》1993,7(2):195-213
In this paper, we propose a two level hierarchical control strategy to achieve accurate end-point position of a planar two-link flexible manipulator. The upper level consists of a feedforward rule-based supervisory controller that incorporates fuzzy logic, whereas the lower level consists of conventional controllers that combine shaft position-endpoint acceleration feedback for disturbance rejection properties and shaping of the (joint) actuator inputs to minimize the energy transferred to the flexible modes during commanded movements. The effectiveness of this hierarchical control strategy is verified by experimental results for various movements of the links, in various configurations. In particular, we illustrate how the hierarchical intelligent control strategy performs better than conventional control techniques for endpoint position control in the presence of flexure effects. 相似文献
19.
Isabela Monteiro Cesar Oyama Erick Gabriel Ribeiro dos Anjos Guilherme Ferreira de Melo Morgado Tayra Rodrigues Brazil María Cristina Kantun-Uicab Fabio Roberto Passador 《应用聚合物科学杂志》2024,141(7):e54952
Glassy carbon (GC) and graphene nanoplatelets (GNP) were used as fillers for the preparation of antistatic and biodegradable composites based on poly (lactic acid)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PLA/PHBV) blend. In this work, PLA/PHBV (80/20) blends with the addition of different GC contents (0.1, 0.3, and 0.5 wt%) were prepared by melt mixing using a twin-screw extruder, and specimens were injection molded. Furthermore, hybrid composites were prepared with the addition of 5 wt% of GNP and different GC contents (0.1, 0.3, and 0.5 wt%) using the same processing. The effect of the addition of GC and GNP on the mechanical, electrical, and electromagnetic properties and its effect on the biodegradability of the PLA/PHVB blend was evaluated. The simultaneous addition of GC (0.3 and 0.5 wt%) and GNP (5 wt%) significantly increases the elastic modulus and decreases the electrical resistivity, becoming suitable for electrostatic discharge protection packaging applications. The hybrid composite GC0.5/GNP5 reached a maximum value of total attenuation (4.5 dB), which corresponds to 60% EMI shielding. The degree of crystallinity affects biodegradability more than the type or presence of carbon material. After 110 days of anaerobic biodegradation, the hybrid composite exhibited 10% biodegradability due to the high degree of crystallinity that hinders the biodegradability process. The hybrid composites with the addition of GC and GNP are very promising for use in antistatic packaging. 相似文献
20.
Erick C. López-Vidaña Benjamín A. Rojano Isaac Pilatowsky Figueroa Karol Zapata 《Chemical Engineering Communications》2016,203(6):809-821
In recent years, interest toward berries has increased (e.g., Myrciaria cauliflora or jaboticaba) because of their high phenolic content (phenolic acids, flavonoids, and anthocyanins) that has been associated with positive effects on consumer health and which play an important role in the antioxidant properties of food. This study analyzed the sorption isotherms, thermodynamic properties of sorption (isosteric heat and Gibbs free energy), and the evolution of the antioxidant capacity during the drying process. The effects of drying temperatures of 40°, 50°C, and 60°C on the antioxidant capacity and thermodynamic properties of sorption were evaluated. The gravimetric static method for sorption isotherm determination over a range of relative humidity levels from 0.10 to 0.90 was used. The sorption isotherms exhibited a Type II behavior, typical for many foods. The Guggenheim, Anderson, and Boer (GAB); Oswin; Peleg; and Lewicki models were used to fit the experimental data, and it was determined that the GAB and Peleg models were most appropriate for describing the sorption curves. The isosteric heat and Gibbs free energy were obtained from the experimental sorption equilibrium. The isosteric heat of adsorption decreased when the moisture content increased, while the Gibbs free energy increased. In addition, the phenolic content and antioxidant capacity increased while drying at 50°C and 60°C, whereas these factors decreased at 40°C. Our results provide the food industry with information concerning the best drying conditions to preserve antioxidant properties. 相似文献