Resultados de investigación

De data base shows the results of a new methodology to determine the breakage distribution function parameters to be used in High pressure grinding rolls modelling. The piston die test tries to simulate a high pressure enviroment, thus the resulted particle size distribution can be normalized to describe a breakage mechanism. Furthermore, one example of how to obtain the breakage function parameters is presented., The modelling of high pressure grinding rolls is described by the population balance model, a mass balance which includes several functions that are related to the mineral characteristics, material kinetics and operative conditions of the device. The breakage distribution function is one of these functions and refers to the way in which the daughter particles are generated by the process of comminution. The piston-die press is presented as a methodology to determine the breakage distribution function of two different materials, from the mechanical response point of view: altered granite and a cal-silicate material. The aim is to determine the relation between the operative conditions and the mineral characteristics in order to explain and predict the breakage function parameters. The materials were characterised using XRD and single compression strength tests. The altered granite is a brittle material, which generates more fines under single compression conditions compared to bed compression conditions, mainly due to the mineral composition and the response of the material to the breakage action. The cal-silicate material shows a normal trend in its breakage behaviour. As is expected, the mineralogical characterisation is a useful tool to predict the values of the parameters of the breakage distribution function., 1

Using a previous mechanical characterization of two types of material, several lab-test work have been done. The data shows the particle size distribution of these tests, all the inputs and the model simulation presented in the related paper to this data base. The new mathematical approach use the operative conditions and the feed particle size distribution to obtain a product, which is compared with the lab-test results, An improved approach is presented to model the product particle size distribution resulting from grinding in high-pressure roll crusher with the aim to be used in standard high-pressure grinding rolls (HPGR). This approach uses different breakage distribution function parameter values for a single particle compression condition and a bed compression condition. Two materials were used for the experiments; altered Ta-bearing granite and a calc-silicate tungsten ore. A set of experiments was performed with constant operative conditions, while varying a selected condition to study the influence of the equipment set-up on the model. The material was comminuted using a previously determined specific pressing force, varying the feed particle size, roll speed and the static gap. A fourth group of experiments were performed varying the specific pressing force. Experimental results show the high performance of the comminution in a high-pressure environment. The static gap was the key in order to control the product particle size. A mathematical approach to predict the product particle size distribution is presented and it showed a good fit when compared to experimental data. This is the case when a narrow particle size fraction feed is used, but the fit became remarkably good with a multi-size feed distribution. However, when varying the specific pressing force in the case of the calc-silicate material, the results were not completely accurate. The hypothesis of simultaneous single particle compression and bed compression for different size ranges and with different parameters of the distribution function was probed and reinforced by various simulations that exchanged bed compression parameters over the single particle compression distribution function, and vice versa., 1

STM-ncAFM from IMDEA Nanociencia Institute and CATRIN under ultra-high vacuum conditions at 4K, acquired between 2018 and 03.2023, *.txt *.jpg *.docx files, *.WSxM files can be opened with Origin

We propose a scan test for the presence of spatial groupwise heteroskedasticity in cross-sectional data. The scan approach has been used in different fields before, including spatial econometric models, to detect instability in mean values of variables or regression residuals. In this paper, we extend its use to second order moments. Using large Monte Carlo simulations, we check the reliability of the proposed scan procedure to detect instabilities in the variance, the size and power of the test and its accuracy to find spatial clusters of observations with similar variances. Finally, we illustrate the usefulness of this test to improve the specification search in a spatial hedonic model, with an empirical application on housing prices in Madrid. | How to cite the database (APA style): Chasco, C.; Le Gallo, J. & López, FF. (2018). A scan test for spatial groupwise heteroscedasticity in cross-sectional models with an application on houses prices in Madrid [Data set & Code]. (doi: 10.23728/b2share.b862dd888bbd4799a86896c0763668a4).

Surfactants are often used in oral health products. The use these compounds has been related to several oral diseases. However, oral care products without surfactants have been unsuccessful as these components fulfil several functions. They serve as solubilizing, dispersing, emulsifying and wetting agents. They also promote foaming which provides a perception of cleanliness. Thus, a widespread use of oral care formulations without surfactants is unrealistic. It is then of interest to identify those with lower adverse effects. In this context, it is of great value to understand how surfactants interact with the first interfacial layer that they encounter i.e., salivary pellicles. These are proteinaceous nm-thick films that form on any type of surface upon exposure to saliva and that fulfil many functions e.g., they protect, lubricate and hydrate underlying oral tissues. The applicants have previously shown that Neutron Reflectometry (NR) is a powerful tool to investigate the structure of salivary pellicles. Here, we propose to use NR to study how their structure is affected by surfactants of relevance within oral care formulations.