388 research outputs found
Influence of CaCl2.2H2O Content on the Productive Process of Composites from Cotton Gin Waste
AbstractPrevious studies have shown the feasibility of production of masonry blocks and panels from agglomeration of cotton gin waste and calcium binders. Cotton gin waste is a serious problem for ginning plants, because in Argentina approximately 300,000 t of lignocellulosic wastes are produced annually without any final disposal destination. The accumulation of these residues is associated with pests and fire hazards. Since these composites are produced with simple equipment and a minimum energy requirement, their cost depends mainly on the binder (Portland cement) used and the process efficiency, since with a high productivity model, labor and equipment depreciation costs are significantly reduced. This paper analyzes the influence of CaCl2.2H2O (added as an accelerator for cement paste strength) on the minimum molding time required for composites manufacturing. A central composite experimental design was developed in order to study the interrelated variables. The influence of CaCl2.2H2O content on physical-mechanical cement paste properties and their relationship with composites stability are also evaluated. The results of this work show that CaCl2.2H2O content has significant influence on the efficiency of composites manufacturing as it reduces the molding time required
Autotrophic and heterotrophic denitrification for simultaneous removal of nitrogen, sulfur and organic matter
24 PĂĄginas; 5 Tablas; 5 FigurasThe aim of this investigation was to assess the startup and operation of a laboratory-scale hybrid UASB-Anaerobic Filter Reactor (UASFB) of 1 L volume, kept at 30°C, in order to carry out a simultaneous autotrophic and heterotrophic denitrification process. First, the heterotrophic and autotrophic populations were separately enriched, with specific cultures and subsequently the UASFB was inoculated with 2 g Lâ1 of volatile suspended solids (VSS), with a ratio of 1.5:1 (autotrophs: heterotrophs). The influent or synthetic wastewater used was composed of: Na2S2O3·5H2O, CH3COOK, NaNO3, NaHCO3, K2HPO4, NH4Cl and saline solution. The concentrations varied depending on the organic loading rate (OLR), nitrogen loading rate (NLR) and sulfur loading rate (SLR) applied. In the UASFB reactor, two experimental conditions were tested and assessed: (i) COD/N ratio of 3.6 and SLR of 0.75 kg S mâ3 dâ1; and (ii) COD/N ratio of 5.8 and SLR of 0.25 kg S mâ3 dâ1. The results obtained demonstrated that an inoculum coming from an anaerobic reactor was able to carry out the process, obtaining a maximum nitrate removal of 85.3% in the first stage of operation and 99.5% in the second stage. The recovery of sulfur in form of sulfate in the effluent did not present a tendency to stabilize during the measured time, with a maximum thiosulfate removal of 32.5%, when the SLR was lowered to 0.25 kg S mâ3 dâ1. The maximum organic matter elimination, measured as COD, was 75.8%, which indicates the relatively good performance and behavior of the heterotrophic microorganisms.The authors wish to express their gratitude to FONDECYT, Project No. 1130108 (Chile), for its financial support.Peer reviewe
Mechanical behavior of tungsten-vanadium-lanthana alloys as function of temperature
The mechanical behavior of three tungsten (W) alloys with vanadium (V) and lanthana (La2O3) additions (Wâ4%V, Wâ1%La2O3, Wâ4%Vâ1%La2O3) processed by hot isostatic pressing (HIP) have been compared with pure-W to analyze the influence of the dopants. Mechanical characterization was performed by three point bending (TPB) tests in an oxidizing air atmosphere and temperature range between 77 (immersion tests in liquid nitrogen) and 1273 K, through which the fracture toughness, flexural strength, and yield strength as function of temperature were obtained.
Results show that the V and La2O3 additions improve the mechanical properties and oxidation behavior, respectively. Furthermore, a synergistic effect of both dopants results in an extraordinary increase of the flexure strength, fracture toughness and resistance to oxidation compared to pure-W, especially at higher temperatures. In addition, a new experimental method was developed to obtain a very small notch tip radius (around 5â7 ÎŒm) and much more similar to a crack through the use of a new machined notch. The fracture toughness results were lower than those obtained with traditional machining of the notch, which can be explained with electron microscopy, observations of deformation in the rear part of the notch tip.
Finally, scanning electron microscopy (SEM) examination of the microstructure and fracture surfaces was used to determine and analyze the relationship between the macroscopic mechanical properties and the micromechanisms of failure involved, depending on the temperature and the dispersion of the alloy
"Resonance" phenomena in thermal diffusion processes in two-layer structures
The dependence on chopper frequency of the effective thermal diffusivity and
effective thermal conductivity in photoacoustic experiments is discussed. The
theoretical model of a two-layer structure at rear-surface illumination in the
high frequency limit is considered. It is shown that the effective thermal
diffusivity presents ``resonance'' while the effective thermal conductivity
sharply changes its magnitude and sign. Such ``resonant'' behavior strongly
depends on the surface thermal conductivities associated with the interface
thermal contacts.Comment: 13 pages, 3 figure
Comportamiento mecĂĄnico en funciĂłn de la temperatura de aleaciones wolfranio-vanadio
Libro de proceedings de: XI Congreso Nacional de Materiales, Zaragoza, 23 junio 2010En esta investigaciĂłn se evalĂșa el comportamiento mecĂĄnico del wolframio puro y de dos de sus aleaciones con contenidos de 2% y 4% de vanadio, fabricadas mediante prensado isostĂĄtico en caliente (HIP). La caracterizaciĂłn mecĂĄnica se ha realizado mediante ensayos de flexiĂłn en tres puntos en atmĂłsfera oxidante a distintas temperaturas comprendidas entre temperatura ambiente y 1000 ÂșC. Adicionalmente, se han realizado ensayos en inmersiĂłn en nitrĂłgeno lĂquido para los de -197 ÂșC. Estos Ășltimos valores pueden servir para una determinaciĂłn mĂĄs precisa de la temperatura la transiciĂłn dĂșctil-frĂĄgil en Ă©stos materiales, y de su posible comportamiento plĂĄstico o frĂĄgil a temperatura ambiente. Mediante estos ensayos ha sido posible obtener la tenacidad de fractura, la resistencia mecĂĄnica, el lĂmite elĂĄstico y el mĂłdulo de elasticidad en funciĂłn de la temperatura. AsĂ mismo, se ha determinado la densidad y la dureza Vickers para dos cargas distintas, lo que permitido determinar la influencia de este parĂĄmetro en la medida realizada. Adicionalmente, se han examinado mediante microscopia electrĂłnica de barrido las superficies de fractura. De esta forma ha sido posible determinar el modo de rotura y analizar la relaciĂłn de las propiedades mecĂĄnicas macroscĂłpicas con los micromecanismos de fallo involucrados.Este trabajo ha sido financiado por EFDA/CIEMAT WP08-09-MAT-WWALLOY, Ministerio de Ciencia e InnovaciĂłn, MAT2007-29278-E, BIA2004-04835, y MAT2009- 13979-C03-02, y Comunidad de Madrid, SS2009/MAT-1585 y S2009/ENE-1679Publicad
Comportamiento mecĂĄnico en funciĂłn de la temperatura de aleaciones wolframio-vanadio.
En esta investigaciĂłn se evalĂșa el comportamiento mecĂĄnico del wolframio puro y de dos de sus aleaciones con contenidos de 2% y 4% de vanadio, fabricadas mediante prensado isostĂĄtico en caliente (HIP). La caracterizaciĂłn mecĂĄnica se ha realizado mediante ensayos de flexiĂłn en tres puntos en atmĂłsfera oxidante a distintas temperaturas comprendidas entre temperatura ambiente y 1000 ÂșC. Adicionalmente, se han realizado ensayos en inmersiĂłn en nitrĂłgeno lĂquido para los de -197 ÂșC. Estos Ășltimos valores pueden servir para una determinaciĂłn mĂĄs precisa de la temperatura la transiciĂłn dĂșctil-frĂĄgil en Ă©stos materiales, y de su posible comportamiento plĂĄstico o frĂĄgil a temperatura ambiente. Mediante estos ensayos ha sido posible obtener la tenacidad de fractura, la resistencia mecĂĄnica, el lĂmite elĂĄstico y el mĂłdulo de elasticidad en funciĂłn de la temperatura. AsĂ mismo, se ha determinado la densidad y la dureza Vickers para dos cargas distintas, lo que permitido determinar la influencia de este parĂĄmetro en la medida realizada. Adicionalmente, se han examinado mediante microscopia electrĂłnica de barrido las superficies de fractura. De esta forma ha sido posible determinar el modo de rotura y analizar la relaciĂłn de las propiedades mecĂĄnicas macroscĂłpicas con los micromecanismos de fallo involucrados
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Advances in the Application and Utility of Subseasonal-to-Seasonal Predictions
The subseasonal-to-seasonal (S2S) predictive time scale, encompassing lead times ranging from 2 weeks to a season, is at the frontier of forecasting science. Forecasts on this time scale provide opportunities for enhanced application-focused capabilities to complement existing weather and climate services and products. There is, however, a âknowledgeâvalueâ gap, where a lack of evidence and awareness of the potential socioeconomic benefits of S2S forecasts limits their wider uptake. To address this gap, here we present the first global community effort at summarizing relevant applications of S2S forecasts to guide further decision-making and support the continued development of S2S forecasts and related services. Focusing on 12 sectoral case studies spanning public health, agriculture, water resource management, renewable energy and utilities, and emergency management and response, we draw on recent advancements to explore their application and utility. These case studies mark a significant step forward in moving from potential to actual S2S forecasting applications. We show that by placing user needs at the forefront of S2S forecast developmentâdemonstrating both skill and utility across sectorsâthis dialogue can be used to help promote and accelerate the awareness, value, and cogeneration of S2S forecasts. We also highlight that while S2S forecasts are increasingly gaining interest among users, incorporating probabilistic S2S forecasts into existing decision-making operations is not trivial. Nevertheless, S2S forecasting represents a significant opportunity to generate useful, usable, and actionable forecast applications for and with users that will increasingly unlock the potential of this forecasting time scale
Response of Horticultural Soil Microbiota to Different Fertilization Practices
Environmentally friendly agricultural production necessitates manipulation of microbeâplant interactions, requiring a better understanding of how farming practices influence soil microbiota. We studied the effect of conventional and organic treatment on soil bacterial richness, composition, and predicted functional potential. 16S rRNA sequencing was applied to soils from adjacent plots receiving either a synthetic or organic fertilizer, where two crops were grown within treatment, homogenizing for differences in soil properties, crop, and climate. Conventional fertilizer was associated with a decrease in soil pH, an accumulation of Ag, Mn, As, Fe, Co, Cd, and Ni; and an enrichment of ammonia oxidizers and xenobiotic compound degraders (e.g., Candidatus Nitrososphaera, Nitrospira, Bacillus, Pseudomonas). Soils receiving organic fertilization were enriched in Ti (crop biostimulant), N, and C cycling bacteria (denitrifiers, e.g., Azoarcus, Anaerolinea; methylotrophs, e.g., Methylocaldum, Methanosarcina), and disease-suppression (e.g., Myxococcales). Some predicted functions, such as glutathione metabolism, were slightly, but significantly enriched after a one-time manure application, suggesting the enhancement of sulfur regulation, nitrogen-fixing, and defense of environmental stressors. The study highlights that even a single application of organic fertilization is enough to originate a rapid shift in soil prokaryotes, responding to the differential substrate availability by promoting soil health, similar to recurrent applications.This work was supported by the Earth Microbiome Project; the METAMAHA project funded by the Basque Governmentâs Department of Industry, Trade, and Tourism (SAIOTEK program; S-PE13UN130); and IT1014-16 and IT1213-19 Consolidated Research Group Projects
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