1,769 research outputs found
ObtenciĂłn de estireno a partir de residuos de poliestireno expandido mediante pirolisis catalĂtica
En este trabajo se estudiĂł un proceso de pirolisis catalĂtica que permite transformar los residuos de poliestireno expandido a su monĂłmero de estireno, con la finalidad de ser reutilizado en la industria del poliestireno para la fabricaciĂłn de nuevos productos y, de esta manera, efectuar su reciclaje. El poliestireno, a diferencia de otros polĂmeros, tiene un gran potencial para producir su monĂłmero a travĂ©s de un proceso de pirolisis y es posible aumentar su rendimiento utilizando un catalizador adecuado. Debido a la baja densidad del poliestireno expandido (0.012 g/mL) es necesario reducir su volumen, disolviĂ©ndolo en un solvente apropiado. Los criterios para seleccionar el solvente fueron: buena solubilidad del poliestireno, no estar clasificado como tĂłxico, tener bajo costo y disponibilidad en el mercado. Se realizaron pruebas con diferentes catalizadores bĂĄsicos para determinar cuĂĄl es el que proporciona el mejor rendimiento. Se determinĂł la cinĂ©tica de la reacciĂłn de pirolisis del poliestireno expandido.In this work it was studied a catalytic pyrolysis process that allows to transform waste expanded polystyrene to its styrene monomer, in order to be reused in the polystyrene industry for the manufacture of new products and, in this way, to carry out its recycling. Polystyrene, unlike other polymers, has great potential to produce its monomer through a pyrolysis process and it is possible to increase its yield using a suitable catalyst. Due to the low density of expanded polystyrene (0.012 g/mL) it is necessary to reduce its volume, dissolving it into an appropriate solvent. The criteria for selecting the solvent were: polystyrene good solubility, not being classified as toxic, having low cost and availability in the market. Tests were performed with different basic catalysts to determine which one provides the best yield. The kinetics of expanded polystyrene pyrolysis reaction were determined
Soil and leaf mineral element contents in mediterranean vineyards: bioaccumulation and potential soil pollution
The study reported here concerns the geochemical distributions of macro- and trace elements (including potentially toxic elements, PTEs) in the vineyard soils of Alcubillas, which is one of the oldest, albeit not world-renowned, wine-growing areas in La Mancha (Central Spain). Soil and leaf samples were analyzed by X-ray fluorescence spectrometry to ascertain the levels of various elements in the soil and the plant. The potential toxicity of the elements was assessed with regard to the development of the vineyard. Despite the fact that fertilizers and pesticides are employed in the vineyards in this area, the results showed that the levels of trace elements in the soil samples did not exceed the reference values according the pedogeochemical values for the region and Spain. This finding suggests that the study area is not polluted, and therefore, there are hardly any traces of anthropogenic contamination. The Biological Absorption Coefficient (BAC) was calculated to assess the assimilation of various elements from the soil to the leaves, and differences were found in the element absorption capacity of the vines. Some elements were not taken up by Vitis vinifera despite elements like Zr and Rb being present in relatively high concentrations in the soil. The production in these soils does not represent a threat to human health or the ecosystem, because the farmers in this area are extremely careful to preserve the environment and they only farm to achieve moderate yields of grapes per hectar
First findings and molecular data of phlebotomus mascittii (diptera: Psychodidae) in the cantabrian cornice (northern spain)
Phlebotomus (Transphlebotomus) mascittii Grassi, 1908 (Diptera: Psychodidae) has been found in several European countries. In Spain, sporadic records were reported in the early ''80s in Catalonia (Northeast Spain), and it was never detected again. Recent entomological surveys carried out between 2004 and 2020 revealed the presence of several specimens of P. mascittii in Spain. The species identification was confirmed by both morphological and molecular analyses. The analyzed specimens belonged to the haplotype (COI_2) defined by one polymorphic site compared to other European specimens. Phlebotomus mascittii was found in low population densities in rural areas associated with livestock farms and in an urban cemetery during the summer season. This study provides the first records of this species in various localities along the Cantabrian cornice (Northern Spain) and represents its westernmost observation in the Palearctic region. The implications of the finding of this uncommon species are discussed at different levels, with emphasis on its suspected role in the transmission of leishmaniosis. © The Author(s) 2021
Optimal numerical design of bucket elevators using discontinuous deformation analysis
Bucket elevators are efficient machines to transport granular materials in industrial and civil engineering applications. These materials are composed of hundreds, thousands or even more particles, the global behavior of which is defined by contact interactions. The first attempts to analyze the transportation of granular materials were treated by very simple continuum methods that do not take into account these interactions, producing simulations that do not fit the experimental results accurately. Given the internal discontinuity nature of granular media, it is reasonable to use numerical methods to model their behavior, such as discontinuous deformation analysis (DDA)-a member of the discrete element method family that started to be used in the 90s to analyze similar problems. The version of DDA used in the current work treats grains as rigid circular particles with friction, damping and eventually cohesion with the objective of simulating and analyzing in detail the discharge of granular materials with bucket elevators. A deterministic computer code has been implemented and validated against simplified analytical formulae and experimental results taken from the literature. This computer code is then used to obtain optimum two-dimensional bucket geometries under specific working conditions. The optimization aims to maximize transport distance and to minimize remaining material, taking into account bucket velocity and the properties of the grains. The resulting geometries are discussed and compared against standard designs.J.L. Perez-Aparicio, R. Bravo were partially supported by the MFOM I+D (2004/38), both by MICIIN #BIA 2008-00522 and the first also by Polytechnic University of Valencia under grant PAID 05-10-2674. J.J. Gomez-Hernandez was partially supported by MICIIN #CGL 2011-23295.PĂ©rez Aparicio, JL.; Bravo, R.; GĂłmez-HernĂĄndez, JJ. (2014). Optimal numerical design of bucket elevators using discontinuous deformation analysis. Granular Matter. 16(4):485-498. https://doi.org/10.1007/s10035-014-0485-5S485498164Rademacher, F.: Non-spill discharge characteristics of bucket elevators. Powder Technol. 22(2), 215â241 (1979)Koster, K.: Bulk material discharge of bucket elevators, especially high-capacity bucket elevators. [zum schuettgutabwurf bei becherwerken, insbesondere bei hochleistungsbecherwerken]. Aufbereitungs-Technik 25(8), 450â463 (1984)Koster, K.: Use of high-capacity bucket elevators in the cement industry. [zum einsatz von hochleistungsbecherwerken in der zementindustrie]. Zement-Kalk-Gips 33(3), 116â119 (1980)Koster, K.: Development and state of the art in heavy-duty bucket elevators with central chainsâpart 2 [entwicklung und stand der technik von hochleistungs-becherwerken mit zentralketteâteil 2]. ZKG Int. 49(4), 173â187 (1996)Koster, K.: Centrifugal discharge of bucket elevators. Bulk Solids Handl. 5(2), 449â460 (1985)Koster, K.: Problem of complete emptying of high-speed elevator buckets. Aufbereitungs-Technik 27(9), 471â481 (1986)Korzen, Z.: Mechanics of gravitational discharge of cell-less bucket wheels in reclaiming machines. Bulk Solids Handl. 7(6), 801â812 (1987)Korzen, Z., Dudek, K.: Mathematical model of the operational efficiency of a multibucket centrifugal discharge wheel [model matematyczny wydajnosci roboczego procesu kola wieloczerpakowego z odsrodkowym wysypem]. Politechnika Warszawska Prace Naukowe Mechanika 1(121), 187â199 (1989)Shi, G., Goodman, R.: Two dimensional discontinuous deformation analysis. Int. J. Numer. Anal. Methods Geomech. 9(6), 541â556 (1985)PĂ©rez-Aparicio, J., Bravo, R.: Discrete Elements, vol. 2, pp. 41â77. Consorcio TCN (2006)Shi, G.: Discontinuous Deformation Analysis: A New Model for the Statics and Dynamics of Block Systems. Ph.D. thesis, University of California, Berkeley (1988)Moosavi, M., Grayeli, R.: A model for cable bolt-rock mass interaction: integration with discontinuous deformation analysis (DDA) algorithm. Int. J. Rock Mech. Min. Sci. 43(4), 661â670 (2006)PĂ©rez-Aparicio, J., Bravo, R., Ortiz, P.: Refined element discontinuous numerical analysis of dry-contact masonry arches. Eng. Struct. 48, 578â587 (2013)McBride, W., Sinnott, M., Cleary, P.: Discrete element modelling of a bucket elevator head pulley transition zone. Granul. Matter 13(2), 169â174 (2011)Kruggel-Emden, H., Sudbrock, F., Wirtz, S., Scherer, V.: Experimental and numerical investigation of the bulk behavior of wood pellets on a model type grate. Granul. Matter 14(6), 681â693 (2012)Walton, O., Moor, C., Gill, K.: Effects of gravity on cohesive behavior of fine powders: implications for processing lunar regolith. Granul. Matter 9(5), 353â363 (2007)Gao, Y., Muzzio, F., Ierapetritou, M.: Optimizing continuous powder mixing processes using periodic section modeling. Chem. Eng. Sci. 80, 70â80 (2012)Shmulevich, I.: State of the art modeling of soil-tillage interaction using discrete element method. Soil Tillage Res. 111(1), 41â53 (2010)Moon, T., Oh, J.: A study of optimal rock-cutting conditions for hard rock tbm using the discrete element method. Rock Mech. Rock Eng. 45(5), 837â849 (2012)Makokha, A., Moys, M., Bwalya, M., Kimera, K.: A new approach to optimising the life and performance of worn liners in ball mills: experimental study and DEM simulation. Int. J. Miner. Process. 84(1â4), 221â227 (2007)BaleviÄius, R., KaÄianauskas, R., Mroz, Z., Sielamowicz, I.: Discrete element method applied to multiobjective optimization of discharge flow parameters in hoppers. Struct. Multidiscip. Optim. 31(3), 163â175 (2006)Hu, L.: Gradual deformation and iterative calibration of Gaussian-related stochastic models. Math. Geol. 32(1), 87â108 (2000)Bravo, R., PĂ©rez-Aparicio, J., Laursen, T.: An energy consistent frictional dissipating algorithm for particle contact problems. Int. J. Numer. Methods Eng. 92(9), 753â781 (2012)Belytschko, T., Liu, W., Moran, B.: Nonlinear Finite Elements for Continua and Structures. Wiley, New York (2000)Beckert, R., Föll, R.: Untersuchung der abwurfverhĂ€ltnisse an kettenbecherwerken. Förden Heben 1(15), 833â836 (1966)Jaskulski, A.: Engineer-to-order approach to high speed bucket elevator design in a small-enterprise. Appl. Eng. Agric. 24(5), 545â557 (2008)Beverley, G.: Mechanics of High Speed Bucket Elevator Discharge. Ph.D. thesis. University of Newcastle (1986)Beverley, G., Roberts, A., Hayes, J.: Mechanics of high speed elevator discharge. Bulk Solids Handl. 3(4), 853â859 (1983)Korzen, Z., Dudek, K.: Reclaiming with a high-speed bucket wheel with centrifugal discharge. Bulk Solids Handl. 11(3), 615â626 (1991)Bravo, R., PĂ©rez-Aparicio, J., Laursen, T.: An enhanced energy conserving time stepping algorithm for frictionless particle contacts. Int. J. Numer. Methods Eng. 85(11), 1415â1435 (2011)Jaskulski, A.: Methodology of Multi-Criteria Optimization of Appliances for Vertical Grain Transportation. Ph.D. thesis. Warsaw University of Technology (1992
Trichomyia andina sp. nov., un nuevo psicĂłdido no hematĂłfago (Diptera: Psychodidae: Trichomyiinae) de Colombia
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Session D7: Fishway with Two Entrance Locations: Understanding its importance for Iberian Barbel
Abstract
In recent years, in the Iberian Peninsula, many fish passes have been built and improved. To ensure the proper operation of these, it is essential to carry out an evaluation and subsequent monitoring, considering both biologic and hydraulic aspects. We analyze the performance of Iberian barbel âLuciobarbus bocagei (Steindachner, 1864)â in a technical fishway: pool and weir, with bottom orifice. It is located in the Josefina hydropower plant (Duero River, Valladolid, Spain). Fish ladder has two fish entrances: one in the turbine outlet channel and another in the natural river course. Both the most relevant hydraulic values (flow, velocity, volumetric energy dissipation) and biological parameters (movement pattern, attraction, entry and passage) were measured.
Biological assessment was conducted in the spawning season using PIT tag technology. The main influence on upstream movement was river discharge. There were no preferences between path selection; and ascent success and transit time were similar between two entrances.. Results highlight the importance of two access points for improve entrance and decrease migration delay
Geochemical influence of soil on leaf and grape (Vitis vinifera L. 'Cencibel') composition in La Mancha region (Spain)
The main purpose of the study was to evaluate major and trace elements contained in topsoil from representative plots of vineyards located in La Mancha, Spain, to obtain an elemental fingerprint of vines. The samples evaluated were obtained from topsoil in six different plots, belonging to the region of La Mancha, characterized by the cultivation of vineyards (near 189.127 ha). Twenty different vines from each plot were chosen to take samples from grapes, petioles and leaves. Analyses were carried out by X-ray Fluorescence applied on soils and dried vegetal matter. Biological Absorption Coefficient (BAC) was calculated to assess the uptake of minerals by vines as a function of their specific content in soil. The BAC in leaves and grapes was very similar for all studied elements. High contents of Ca, Sr, Ni and rare earth elements (La, Ce and Nd) were found along with low contents in Al, Zr, Ba, Cu, Zn and Pb, and normal contents in the rest of the elements. BAC in grapes was lower for the majority of the studied elements but it is interesting to underline the contents of Cs, K, Nb, Ce, Zn and Sr as possible markers of soil fingerprinting in the resulting wines.
Suppression of Coulomb-nuclear interference in the near-barrier elastic scattering of 17 Ne from 208 Pb
The proton drip-line nucleus 17Ne is considered a good candidate for a Borromean two-proton halo with a 15O + p+ pstructure. Angular distributions of the elastic scattering and inclusive 15O production for a 136 MeV 17Ne beam incident on a 208Pb target were measured for the first time at the SPIRAL1 facility, GANIL. Use of the GLORIA detector array allowed high-resolution data over a wide angular range from 20âŠup to 95âŠin the laboratory frame to be obtained. The elastic scattering angular distribution shows similarities with those for both 6He and 20Ne at equivalent collision energies with respect to the corresponding Coulomb barriers, exhibiting the suppression of the Coulomb rainbow peak characteristic of strong coupling. Optical model and coupled channel fits suggest that this is due to a combination of coupling to low-lying quadrupole resonances and Coulomb dipole coupling to the low-lying continuum, although their relative importance depends on the relevant B(E2)values which remain to be firmly determined
Contribution to van der Waerden's conjecture
AbstractIn this paper, we give two different elementary proofs for the inequality which states that the permanent of doubly stochastic matrices is greater than or equal to (n!/nn). This inequality was proved earlier by the author, and independently by Egorychev and Falikman
Coupling to breakup channels using a transformed harmonic oscillator basis
The application of a recently proposed procedure for discretizing the continuum to collision processes
involving weakly bound nuclei is studied. In particular, the coupling to breakup states in the collision of d
1208 Pb at 50 MeV is discussed. For illustrative purposes, only the s-wave component of the bound state of the
deuteron is considered, and the study is restricted to the case of nuclear s-wave breakup. The continuum
discretization procedure provides a basis of transformed harmonic oscillator wave functions to accomplish the
necessary calculations. Appropriate convergence of the elastic and breakup cross sections with increasing
dimension of the basis is reported. In addition, it is shown that the results obtained converge to those of a
standard continuum discretized coupled channels calculation, with the advantage that the convergence of the
method is determined by only one parameter, namely the dimension of the basis
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