Effect of kind of acid and the solid fraction on the viscosity by the γ-Al2O3 nanofiber in the form of precursor slurry for the final ceramic

Adrián Zamorategui,Oscar Coreño,Julio Del Angel,Satoshi Tanaka 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.7

Nanofibers of gamma alumina were dispersed in acid aqueous media and the effect of hydrochloric and nitric acid on viscositywas investigated. The viscosities of the aqueous suspensions were determined under controlled shear rate conditions, varyingthe pH and solid concentration. A lower viscosity is observed with nitric acid because the nitrate ion produces stronger doublelayer repulsion, in comparison with that obtained with the chloride ion. It was found that the maximum solid loading in thesuspension at pH 4.5 adjusted with HNO3 and HCl was 42 and 35 wt%, respectively. The isoelectric point (IEP) of the aluminapowder in the suspension occurs at pH 8.5. High solid concentrations and a pH close to the IEP produced high viscosity andshear thinning at the low shear rates due to slurry agglomeration. This increases the viscosity of the suspension and diminishesthe final relative density of the slip casting body.

Wind tunnel study of plume dispersion with varying source emission configurations

Adrián R. Wittwer,Acir M. Loredo-Souza,Edith B. Camaño Schettini,Hugo G. Castro 한국풍공학회 2018 Wind and Structures, An International Journal (WAS Vol.27 No.6

The concentration fields in the proximities of a local gas emission source are experimentally analyzed in several combinations of wind incidences and source emissions. These conditions are determined by the plume buoyancy, emission velocity and incident flow wind speed. Concentration measurements are performed by an aspirating probe in a boundary layer wind tunnel. The analysis included the mean concentration values and the intensity of concentration fluctuations in a neutral atmospheric boundary layer flow. Different configurations are tested: an isolated stack in a homogeneous terrain and a stack with a bluff body in close proximity, located windward and leeward from the emission source. The experimental mean concentration values are contrasted with Gaussian profiles and the dilution factor is analyzed with respect to the empirical curves of the minimum dilution. Finally, a study on the plume intermittency is performed in a cross-sectional plane near the emission source. It is possible to highlight the following observations: a) plume vertical asymmetry in the case of an isolated emission source, b) significant differences in the dispersion process related to the relative location of the emission source and bluff body effects, and c) different probabilistic behavior of the concentration fluctuation data in a cross-sectional measurement plane inside the plume.

When we are the violent: The Chechen Islamist guerrillas' discourse on their own armed actions

Adrián Tarín Sanz 한양대학교 아태지역연구센터 2017 Journal of Eurasian Studies Vol.8 No.2

Over the last decades, the strategic profile of the discourse with which wars are narrated has been reinforced. This discourse has also varied in the light of a recent – and alleged – peace culture permeating Western societies. Whereas the war discourse in Russia during the Second Russian-Chechen War has been widely studied, this has not been the case of the rhetoric of the Chechen Islamist guerrillas. The aim of this paper is to contribute to bridging this gap in the academic literature on the North Caucasus, employing to this end a critical discourse analysis (CDA) of a selection of texts posted by the Kavkaz Center (KC) news agency. On the basis of this analysis, it can be concluded that one of the main discursive strategies revolved around the construction of an “us” embodying the Chechen victims of the initial aggression in a conflict provoked by the Russian “other”.

Comparison of Spectral Density Models to Simulate Wind Records

Edén Bojórquez,Omar Payán-Serrano,Alfredo Reyes-Salazar,Adrián Pozos 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.4

Due to the lack of real wind records to perform dynamic analysis of structural systems, civil and structural engineers commonly use simplified and conservative approaches to consider the dynamic effects of wind. With the aim to provide wind records, several studies suggest that the use of spectral density models and configuration of basic wind speed and terrain roughness are adequate to simulate the velocity field of the turbulent wind; however, nowadays there is no enough information to conclude which is the best spectral density model to simulate wind records for various configurations of basic wind speed and terrain roughness. For this reason, in this paper different scenarios are simulated in order to study the behavior of six spectral density functions which are frequently used in wind engineering. It is observed that the models proposed by von Karman, von Karman-Harris and Solari are the best alternative to simulate wind records.

Production of high-quality water by reverse osmosis of milk dairy condensates

Adrián Suárez,Francisco A. Riera 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1

Low-pollution flash cooler (FC) condensates from the direct heat treatment of milk and milk-basedproducts were treated by means of reverse osmosis (RO) in order to obtain high-quality water for use inboilers. The behaviour of the spiral-wound membranes at the pilot-plant scale (8.2m2 surface area) wastested in terms of the permeate flow rate (J) and quality (conductivity and chemical oxygen demand(COD)) as a function of the operation conditions, including the pressure, temperature and volumeconcentration rate (VCR). Response surfaces were drawnwith the aim of obtaining information regardingthe permeate flow rate as well as conductivity and COD reduction in the range of the studied parameters. Based on the experimental data, a plant with a 90% recovery rate (RR)was proposed with the objective ofcarrying out a preliminary economic assessment, which yielded a payback of 1.16 years.

High-energy neutrino follow-up search of gravitational wave event GW150914 with ANTARES and IceCube

Adriá,n-Martí,nez, S.,Albert, A.,André,, M.,Anghinolfi, M.,Anton, G.,Ardid, M.,Aubert, J.-J.,Avgitas, T.,Baret, B.,Barrios-Martí,, J.,Basa, S.,Bertin, V.,Biagi, S.,Bormuth, R. American Physical Society 2016 Physical Review D Vol.93 No.12

<P>We present the high-energy-neutrino follow-up observations of the first gravitational wave transient GW150914 observed by the Advanced LIGO detectors on September 14, 2015. We search for coincident neutrino candidates within the data recorded by the IceCube and ANTARES neutrino detectors. A possible joint detection could be used in targeted electromagnetic follow-up observations, given the significantly better angular resolution of neutrino events compared to gravitational waves. We find no neutrino candidates in both temporal and spatial coincidence with the gravitational wave event. Within +/- 500 s of the gravitational wave event, the number of neutrino candidates detected by IceCube and ANTARES were three and zero, respectively. This is consistent with the expected atmospheric background, and none of the neutrino candidates were directionally coincident with GW150914. We use this nondetection to constrain neutrino emission from the gravitational-wave event.</P>

THE FIRST COMBINED SEARCH FOR NEUTRINO POINT-SOURCES IN THE SOUTHERN HEMISPHERE WITH THE ANTARES AND ICECUBE NEUTRINO TELESCOPES

Adriá,n-Martí,nez, S.,Albert, A.,André,, M.,Anton, G.,Ardid, M.,Aubert, J.-J.,Baret, B.,Barrios-Martí,, J.,Basa, S.,Bertin, V.,Biagi, S.,Bormuth, R.,Bouwhuis, M. C.,Bruijn, R. American Astronomical Society 2016 The Astrophysical journal Vol.823 No.1

<P>We present the results of searches for point-like sources of neutrinos based on the first combined analysis of data from both the ANTARES and IceCube neutrino telescopes. The combination of both detectors, which differ in size and location, forms a window in the southern sky where the sensitivity to point sources improves by up to a factor of 2 compared with individual analyses. Using data recorded by ANTARES from 2007 to 2012, and by IceCube from 2008 to 2011, we search for sources of neutrino emission both across the southern sky and from a preselected list of candidate objects. No significant excess over background has been found in these searches, and flux upper limits for the candidate sources are presented for E-2.5 and E-2 power-law spectra with different energy cut-offs.</P>

Microbial symbionts of Leaf-cutting ants (Atta and Acromyrmex )

Adrián Pinto-Tomás 한국응용곤충학회 2018 한국응용곤충학회 학술대회논문집 Vol.2018 No.10

Mature colonies of leaf-cutting ants (LCA) in the genus Atta are among the largest of any social insect. These “superorganisms” harvest substantial amounts of leaf material per year, which they use to cultivate a specialized symbiotic fungus for food (Basidiomycota, Agaricales, Leucoagaricus). This complex symbiosis is not bipartite as originally thought, as it includes at least four coevolved and integrated organisms: the farming ants, the fungi that the ants cultivate for food, a genus of fungi (Escovopsis) that are specialized mycoparasites of the ant’s fungal gardens, and actinomycete bacteria (genus Pseudonocardia) that the ants culture on their bodies and from which they obtain antibiotics against the Escovopsis parasites. More recently we described an additional symbiosis with Nitrogen-fixing bacteria that colonize the fungus gardens and contribute to supplement the ants’ nutrition. Our present research efforts in Costa Rica focus on potential biotechnological application of the ants’ microbial symbionts, including bioprospecting for novel antibiotics. We currently investigate the contributions of symbiotic bacteria in cellulose degradation within the fungus garden, employing a combination of culture-dependent and independent techniques coupled with ultrastructural analysis based on high resolution microscopy. Further, given that the ants constitute one of the main agricultural pests in Latin America, we study microbial parasites of both the ants and the fungus gardens to develop biocontrol products that can be incorporated into Integrated Management Strategies to control the detrimental effects of these insects.

Evolución Reciente y Situación Actual de la Producción y Difusión de Vehículos Eléctricos a Nivel Global y en Latinoamérica

Federico Dulcich,Dino Otero,Adrián Canzian 한국라틴아메리카학회 2019 라틴아메리카연구 Vol.32 No.4

Encouraged by regulations that seek to mitigate the emission of greenhouse gases, the automotive industry has started an incipient transition to electromobility; so far, this transition has been limited to some of the Western developed countries, as well as Japan, South Korea and China. This transition generates important changes in the technological capabilities and natural resources needed for the development and production of vehicles, and opens a scenario of potential repositioning for firms and countries. In this context, the production of electric vehicles and their regulations are lagging behind in Mexico, Brazil and Argentina – the leading automotive producers in Latin America. However, they have some advantages that could be exploited to reposition themselves in automotive value chains.

Production of rare earth oxides from raw ore in fluidized bed reactor

Adrián Carrillo García,Mohammad Latifi,Said Samih,Jamal Chaouki 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.85 No.-

This study deals with the calcination of a rare earth bearing ore to produce rare earth oxides in afluidizedbed reactor, with the aim of demonstrating the advantage of calcining bigger particles to decomposestable minerals such as monazite by its mineral association within a particle. Rare earth oxides wereproduced by the decomposition of its bearing minerals, bastnäsite and monazite along with the gangues. During the calcination, bastnäsite decomposed at relatively low temperature while monazite reacted CaOat high temperature. The formation of cracks, revealed by BET and SEM analysis, allowed the particle’sdegassing while the size remained constant, thus describing a crackling core behavior. The association of monazite to calcite for bigger particles ( 60 mesh) allowed its decomposition toproduce rare earth oxides with a monazite conversion of 50 %. Also, an extraction process comprised ofcalcination and mild acid leaching enriched the rare earth oxides in the ore by 3.34 and improvedleaching efficiency of the gangues compared to smaller size (enrichment ration of 2.35). Using biggerparticle sizes in the upstream process of a mining industry, i.e. comminution, can also reduce the energyconsumption.