Susceptibility assessment to different types of landslides in the coastal cliffs of Lourinhã (Central Portugal)

The coastal zone of Lourinhã (located in Central Portugal) is characterized by beach–cliff systems,where beaches are narrowand cliffs have notorious slope instability. These cliffs evolve by different types of landslides,which are one of the main sources of natural hazard and risk in this coastal region. In this work, aerial photo interpretation and a systematic field survey were performed in order to obtain an inventory of landslides of the following types: rotational slides, translational slides and debris flows. The entire coast was then split into 261 terrain mapping units. For each unit, landslide predisposing factors were derived and classified: cliff elevation, slope angle (maximum, mean and standard deviation), potential solar radiation, slope curvature (profile and plan), lithological units and geologic structure. The predictive susceptibility models were computed for each type of landslide using a bi-variate statisticalmethod — the Information ValueMethod. The degree of fit and the predictive capacity of the models were assessed using the Effectiveness Ratio, the standard Receiver Operator Characteristic curves and the respective Area Under Curve. Results showthat each landslide typology occurs in particular terrain conditions. Individual susceptibilitymodels evidence better predictive capacity than susceptibility model for total landslides.info:eu-repo/semantics/publishedVersio

Difusividades de compostos bioativos em misturas supercríticas e solventes expandidos

Mestrado em Engenharia QuímicaNas últimas décadas, os fluidos supercríticos têm ganho maior destaque no âmbito dos paradigmas de biorrefinaria e sustentabilidade de processos químicos, surgindo como alternativa verde a muitos solventes orgânicos. Em particular, sendo o dióxido de carbono supercrítico (SC-CO2) o solvente preferido, são necessários valores experimentais e modelos preditivos de difusividades de solutos tanto em SC-CO2 puro como modificado com cossolvente. Esta tese surge como resposta à falta de dados e modelos nesta área, tendo como principal objetivo a medição e posterior modelação dos coeficientes de difusão de eucaliptol em SC-CO2 modificado com 8 % (m/m) de etanol e ainda etanol líquido puro. Recorrendo ao método cromatográfico de abertura de pico (CPB), procedeu-se à medição de difusividades do eucaliptol a diluição infinita (D12), numa gama de temperaturas entre 303.15 K e 333.15 K. Para a mistura SC-CO2 com etanol, a pressões de 150 a 275 bar, obtiveram-se valores compreendidos entre 0.547×10-4 a 1.042×10-4 cm2 s-1. Já em etanol puro, variando a pressão entre 1 e 100 bar, obtiveram-se difusividades entre 0.912×10-5 e 1.578×10-5 cm2 s-1. Os resultados de D12 foram analisados em função da temperatura, pressão, densidade e em coordenadas de Stokes-Einstein. Testou-se também uma série de modelos baseados nas teorias hidrodinâmica e de volume livre, bem como equações empíricas. Os valores calculados e experimentais foram comparados com base no desvio relativo absoluto médio (AARD). Para ambos os sistemas, destacam-se o modelo de dois parâmetros de Dymond-Hildebrand-Batschinski (DHB), o modelo Tracer Liu-Silva-Macedo com um parâmetro (TLSMd), um modelo modificado Stokes-Einstein-1, e as relações empíricas de Magalhães et al. (AARD entre 1.2 e 7.0 %). Em relação ao sistema ternário (eucaliptol na mistura SC-CO2 com etanol) os modelos de Wilke-Chang, Lai-Tan e Vaz et al. (AARD de 8.00, 8.36 e 1.29 %, respetivamente) foram os melhores. Quanto ao sistema binário (eucaliptol em etanol líquido) destaca-se ainda o modelo de Tracer Liu-Silva-Macedo (TLSM) (AARD de 6.75 %). Sugerem-se ainda correções a dois modelos, nomeadamente, à extensão do modelo de Liu-Silva-Macedo para intradifusividades em mixturas Lennard-Jones multicomponente, usando as regras de mistura propostas por Merzliak e Pfenning (LSM-MP) para o sistema ternário, e ao modelo DHB para o sistema binário, tendo-se obtido AARDs de 1.55 % e 3.70 %, respetivamente. Finalmente, procedeu-se à modelação de uma base de dados contendo 1453 pontos experimentais de difusividades correspondentes a 132 sistemas ternários distintos. Esta modelação foi realizada utilizando o modelo LSM-MP, ao qual foi proposta uma correção com base na divisão dos dados em 2 grupos: sistemas líquidos e supercríticos (AARDs de 9.39 % e 9.11 %, respectivamente).Supercritical fluids have gained great importance within the concepts of biorefinery and sustainability of chemical processes. They are considered a “greener” alternatives to a vast group of conventional organic solvents with supercritical carbon dioxide (SC-CO2) being the most preferred. Currently, experimental data and predictive models for diffusivity in SC-CO2 systems are scarce especially regarding SC-CO2 systems modified with a cosolvent. The main objective of this thesis was the experimental determination and modelling of tracer diffusion coefficients (D12) of eucalyptol in SC-CO2 expanded with 8 wt.% ethanol (ternary system) and in pure ethanol (binary system). Furthermore improve the D12 modelling in multicomponent mixtures. Eucalyptol diffusivities were measured by the chromatographic peak broadening technique (CPB) in the temperature range 303.15 to 333.15 K. For the ternary system the values ranged from 0.547×10-4 to 1.042×10-4 cm2·s-1 for pressures between 150–275 bar. For the binary system the values ranged from 0.912×10-5 to 1.578×10-5 cm2·s-1 for pressures between 1-100 bar. The dependency of D12 in terms of temperature, pressure, solvent density, and Strokes-Einstein coordinates were also examined. A series of models based on hydrodynamic and free volume theory and on empirical correlations were tested and compared using the average absolute relative error (AARD) for calculated and experimental values. For both systems, the best results were obtained with the two parameter Dymon-Hildebrand-Batschinski (DHB) model, with the one parameter Tracer Liu-Silva-Macedo (TLSMd) model, with the modified Stokes-Einstein-1 model, and with the Magalhães et al correlations (AARD between 1.2 and 7.0 %). For the ternary system the Wilke-Chang, Lai-Tan, and Vaz et al. models can also be highlighted (achieving AARD of 8.00, 8.36 and 1.29 % respectively). For the binary system the TLSM model achieves an error of 6.75 %. In addition, two corrections are presented to improve model fitting, namely for the extension of Liu-Silva-Macedo model to multicomponent LJ intradiffusivities using mixing rules of Merzliak and Pfenning (LSM-MP) applied to the ternary system and for the DHB model applied to the binary system (AARD of 1.55 % and 3.70 %, respectively). Finally a database containing 132 ternary systems with a total of 1453 experimental diffusivity values was utilized for modeling D12 values, on the basis of the LSM-MP model. The AARD results obtained by splitting the database into two groups, namely liquid and supercritical systems, were 9.39 and 9.11 % respectively

Machine learning models for the prediction of diffusivities in supercritical CO2 systems

The molecular diffusion coefficient is fundamental to estimate dispersion coefficients, convective mass transfer coefficients, etc. Since experimental diffusion data is scarce, there is significant demand for accurate models capable of providing reliable diffusion coefficient estimations. In this work we applied machine learning algorithms to develop predictive models to estimate diffusivities of solutes in supercritical carbon dioxide. A database of experimental data containing 13 properties for 174 binary systems totaling 4917 data points was used in the training of the models. Five machine learning algorithms were evaluated and the results were compared with three commonly used classic models. The best results were found using the Gradient Boosted algorithm which showed an average absolute relative deviation (AARD) of 2.58 % (pure prediction). This model has five parameters: temperature, density, solute molar mass, solute critical pressure and solute acentric factor. For the same dataset, the classic Wilke-Chang equation showed AARD of 12.41 %. The developed model is provided as command line program.publishe

Revisiting Tracer Liu-Silva-Macedo model for binary diffusion coefficient using the largest database of liquid and supercritical systems

This work compiles the largest database of tracer diffusion coefficients (D12) containing 6180 experimental points from 331 non-polar and weakly polar liquid and supercritical systems. Then, the Tracer Liu − Silva − Macedo (TLSM) model and its 1-parameter correlations (TLSMd and TLSMen) are evaluated using this database, taking into account the importance of phenomenological and reliable equations for D12 estimation. The TLSM model achieves good results with absolute average relative deviations (AARD) of 16.84 % while TLSMd and TLSMen show better performance with AARD of 4.53 % and 4.55 %, respectively. All properties and parameters needed for D12 estimation are compiled in Appendix. For comparison, the models of Wilke-Chang and Reddy-Doraiswamy, and the correlations of Magalhães et al. (LJ-1) and Dymond-Hildebrand-Batschinsky (DHB) are also assessed.publishe

Diffusivities of ketones and aldehydes in liquid ethanol by molecular dynamics simulations

The tracer diffusion coefficients of six ketones (propanone, butanone, pentan-2-one, pentan-3-one, hexan-2-one, hexan-3-one) and six aldehydes (methanal, ethanal, propanal, butanal, pentanal and hexanal) in liquid ethanol were computed by classical molecular dynamics (MD) simulations over 303.15-333.15 K and 1-150 bar. The calculated tracer diffusion coefficients, D12, compared very satisfactorily with experimental data from the literature, with average absolute relative deviations (AARD) between 9.48 % and 12.18 % for ketones, and between 6.30 % and 9.11 % for aldehydes. The trends of D12 with solute size and temperature were accurately simulated in all cases, while the weaker influence of pressure was not rigorously reached in all cases when jumping from 1 to 75 bar and then to 150 bar. Furthermore, a temperature-based correction to D12 was introduced, which decreased the AARD values of ketones down to the range 1.52 – 5.16 % and aldehydes to 2.94 – 3.45 %. The structural analyses of the spatial distribution functions and coordination numbers show that ethanol has more affinity with ketones than with aldehydes, though such affinity difference is not always translated to the computed D12 of ketone-aldehyde isomers. Nevertheless, the experimental diffusivities of both families of compounds are only ca. 7 % different, hence within the uncertainties associated with the calculated results.publishe

Diffusion of quercetin in compressed liquid ethyl acetate and ethanol

Supercritical fluids are alternatives to conventional harmful organic compounds. In the case of supercritical fluid extraction, CO2 is the most common solvent and can be advantageously modified with small contents of co-solvents like ethanol and ethyl acetate. The rigorous estimation of the tracer diffusion coefficients (D12) of solutes in supercritical mixtures (CO2 + co-solvent) requires their individual D12 values in pure CO2 and pure co-solvent under the same operating conditions. This essay focuses the diffusivity of quercetin (solute) in two compressed liquid co-solvents (ethanol and ethyl acetate). Quercetin is a natural compound possessing a wide variety of bioactive properties, used as one of the most noticeable dietary antioxidants. The tracer diffusivity measurements are accomplished by the chromatographic peak broadening technique over 303.15–333.15 K and 1–150 bar. The diffusion coefficients lie between 0.414 × 10−5and 0.813 × 10−5 cm2s−1 in ethanol, and between 1.06 × 10−5 and 1.69 × 10−5 cm2s−1 in ethyl acetate. Influence of temperature, pressure and hydrodynamic coordinates is analyzed and discussed based on the most relevant transport theories. Modeling is also carried out with eleven models from the literature and demonstrated the unreliability of predicting equations in opposition to the very good correlations available to fit D12 data. The influence of the accurate estimation of auxiliary properties (like solvent volume and viscosity) upon the calculated tracer diffusivities is also assessed, being possible to detect D12 differences as high as ca. 70 %.publishe

Diffusivities of metal acetylacetonates in liquid ethanol and comparison with the transport behavior in supercritical systems

Diffusion coefficients of chromium(III) acetylacetonate, palladium(II) acetylacetonate, nickel(II) acetylacetonate, vanadyl(II) acetylacetonate, and titanium(IV) oxyacetylacetonate in liquid ethanol were measured by chromatographic peak broadening method (CPB) over the range of temperature 303.15–333.15 K at atmospheric pressure. The dependencies of upon temperature and Stokes–Einstein coordinates were examined in detail. Moreover, the experimental data were modeled using nine equations from the literature to test their accuracy and prediction ability. The lower deviations were achieved by the 2-parameter correlation of Dymond-Hildebrand-Batschinski (0.32–2.17 %), the 1-parameter correlation of Tracer Liu-Silva-Macedo (1.58–3.88 %), and the 2-parameter correlations of Magalhães et al. (0.55–2.32 %). Finally, the proposed correlation based on hydrodynamic approach was found to well represent palladium(II) acetylacetonate and chromium(III) acetylacetonate systems in supercritical carbon dioxide and liquid ethanol, with the average absolute relative deviation of 3.15 and 5.02 %, respectively.publishe

Diffusivities of linear unsaturated ketones and aldehydes in compressed liquid ethanol

For the accurate design, optimization and simulation of chemical processes limited by mass transfer kinetics it is important the knowledge of transport properties, namely, diffusion coefficients, D12. In this work, the D12 values of six unsaturated linear ketones (i.e., propanone, butanone, propan-2-one, propan-3-one, hexan-2-one and hexan-3-one) and three unsaturated linear aldehydes (i.e., butanal, pentanal and hexanal) in (compressed) liquid ethanol were measured at temperatures from 303.15 K to 333.15 K and pressures up to 150 bar. The D12 values of ketones are in the range of 1.28 × 10−5 – 2.89 × 10−5 cm2 s−1 and of the aldehydes are between 1.39 × 10−5 and 2.68 × 10−5 cm2 s−1. The general trends of D12 regarding temperature, pressure, Stokes-Einstein coordinate, and free volume are presented and discussed. The diffusivities of the various ketones position isomers and aldehyde/ketone isomers were statistically compared, being possible to conclude that the former ones exhibit indistinguishable diffusivities while different values appear for aldehydes/ketones isomers. Finally, five models and a machine learning algorithm from the literature were tested to predict/correlate the new data. It is suggested that the TLSM model should be the preferred approach for D12 prediction of linear unsaturated aldehydes and ketones in liquid compressed ethanol.publishe