Calcination of aluminum hydroxide over pressure and residence time

This work investigates the possible effect of pressure and residence time to the reaction of aluminum hydroxide into aluminum oxide. Various pressurized conditions are used as well as the help of various residence times. The aim is to increase the conversion of the reaction with the use of different pressures and residence times. The tests were performed with a laboratory scale fluidized bed reactor at the Outotec R&D Center in Frankfurt. Additional test work such as particle size analysis and differential thermal analysis were also carried out. Some calcined samples were also characterized with X-ray diffraction at the University of Auckland to obtain a reaction pathway when using pressurized conditions. All of the results are then compared with previous results.

Association of early repolarization with risk of cardiac mortality in the general population

Early repolarization, which is characterized by an elevation of the J-point on 12-lead electrocardiography, is a common finding that has been considered as benign for decades. However, in the last years, it has been related with vulnerability to idiopathic ventricular fibrillation and with cardiac mortality in the general population. Recently, 4 potential ECG predictors that could differentiate the benign from the malignant form of early repolarization have been suggested. Any previous study about early repolarization has been done in Spain. Aim. To ascertain whether the presence of early repolarization pattern in a resting electrocardiogram is associated with a major risk of cardiac death in a Spanish general population and to determine whether the presence of potential predictors of malignancy in a resting electrocardiogram increases the risk of cardiac mortality in patients with early repolarization pattern. Methods. We will analyse the presence of early repolarization and the occurrence of cardiac mortality in a retrospective cohort study of 4,279 participants aged 25 to 74 years in the province of Girona. This cohort has been followed during a mean of 9.8 years. Early repolarization will be stratified according to the degree of J-point elevation (≥0.1 mV or ≥0.2 mV), the morphology of the J-wave (slurring, notching or any of these two), the ST-segment pattern (ascending or descending) and the localization (inferior leads, lateral leads, or both). Association of early repolarization with cardiac death will be assessed by adjusted Cox-proportional hazards models

Bayesian Estimation of Noise

In mathematical modeling the estimation of the model parameters is one of the most common problems. The goal is to seek parameters that fit to the measurements as well as possible. There is always error in the measurements which implies uncertainty to the model estimates. In Bayesian statistics all the unknown quantities are presented as probability distributions. If there is knowledge about parameters beforehand, it can be formulated as a prior distribution. The Bays’ rule combines the prior and the measurements to posterior distribution. Mathematical models are typically nonlinear, to produce statistics for them requires efficient sampling algorithms. In this thesis both Metropolis-Hastings (MH), Adaptive Metropolis (AM) algorithms and Gibbs sampling are introduced. In the thesis different ways to present prior distributions are introduced. The main issue is in the measurement error estimation and how to obtain prior knowledge for variance or covariance. Variance and covariance sampling is combined with the algorithms above. The examples of the hyperprior models are applied to estimation of model parameters and error in an outlier case.

Models for the estimation of thermodynamic properties of layered double hydroxides: application to the study of their anion exchange characteristics

Several models for the estimation of thermodynamic properties of layered double hydroxides (LDHs) are presented. The predicted thermodynamic quantities calculated by the proposed models agree with experimental thermodynamic data. A thermodynamic study of the anion exchange process on LDHs is also made using the described models. Tables for the prediction of monovalent anion exchange selectivities on LDHs are provided. Reasonable agreement is found between the predicted and the experimental monovalent anion exchange selectivities.

Estimation of Water Circulation in a Mediterranean Salt Marsh and its Relationship with Flooding Causes

Variations in water volume in small depressions in Mediterranean salt marshes in Girona (Spain) are described and the potential causes for these variations analysed. Although the basins appear to be endorrheic, groundwater circulation is intense, as estimated from the difference between water volume observed and that expected from the balance precipitation / evaporation. The rate of variation in volume (VR = AV / VAt) may be used to estimate groundwater supply ('circulation'), since direct measurements of this parameter are impossible. Volume.conductivity figures can also be used to estimate the quantity of circulation, and to investigate the origin of water supplied to the system. The relationships between variations in the volume of water in the basins and the main causes of flooding are also analysed. Sea storms, rainfall levels and strong, dry northerly winds are suggested as the main causes of the variations in the volumes of basins. The relative importance assigned to these factors has changed, following the recent regulation of freshwater flows entering the system

Quantification of the bond-angle dispersion by Raman spectroscopy and the strain energy of amorphous silicon

A thorough critical analysis of the theoretical relationships between the bond-angle dispersion in a-Si, Δθ, and the width of the transverse optical Raman peak, Γ, is presented. It is shown that the discrepancies between them are drastically reduced when unified definitions for Δθ and Γ are used. This reduced dispersion in the predicted values of Δθ together with the broad agreement with the scarce direct determinations of Δθ is then used to analyze the strain energy in partially relaxed pure a-Si. It is concluded that defect annihilation does not contribute appreciably to the reduction of the a-Si energy during structural relaxation. In contrast, it can account for half of the crystallization energy, which can be as low as 7 kJ/mol in defect-free a-Si

Estimation of surface area and pore volume of activated carbons by methylene blue and iodine numbers

Data of methylene blue number and iodine number of activated carbons samples were calibrated against the respective surface area, micropore volume and total pore volume using multiple regression. The models obtained from the calibrations were used in predicting these physical properties of a test group of activated carbon samples produced from several raw materials. In all cases, the predicted values were in good agreement with the expected values. The method allows extracting more information from the methylene blue and iodine adsorption studies than normally obtained with this type of material.

Estimation of phenotypic diversity in field populations of Magnaporthe grisea from two upland rice cultivars

The phenotypic diversity of Magnaporthe grisea was evaluated based on leaf samples with blast lesions collected from eight commercial fields of the upland rice cultivars 'BRS Primavera' and 'BRS Bonança', during the growing seasons of 2001/2002 and 2002/2003, in Goias State. The number of M. grisea isolates from each field utilized for virulence testing varied from 28 to 47. Three different indices were used based on reaction type in the eight standard international differentials and eight Brazilian differentials. The M. grisea subpopulations of ´Primavera' and 'Bonança', as measured by Simpson, Shannon and Gleason indices, showed similar phenotypic diversities. The Simpson index was more sensitive relation than those of Shannon and Gleason for pathotype number and standard deviation utilizing Brazilian differentials. However, the Gleason index was sensitive to standard deviation for international differentials. The sample size did not significantly influence the diversity index. The two sets of differential cultivars used in this study distinguished phenotypic diversity in different ways in all of the eight subpopulations analyzed. The phenotypic diversity determined based on eight differential Brazilian cultivars was lower in commercial rice fields of 'Primavera' than in the fields of 'Bonança,' independent of the diversity index utilized, year and location. Considering the Brazilian differentials, the four subpopulations of 'BRS Primavera' did not show evenness in distribution and only one pathotype dominated in the populations. The even distribution of pathotype was observed in three subpopulations of 'BRS Bonança'. The pathotype diversity of M. grisea was determined with more precision using Brazilian differentials and Simpson index.

Estimation of existing cable systems in generator-busbar unit and choice the optimal solution for its modernization

The aim of this master’s thesis is to develop an algorithm to calculate the cable network for heat and power station CHGRES. This algorithm includes important aspect which has an influence on the cable network reliability. Moreover, according to developed algorithm, the optimal solution for modernization cable system from economical and technical point of view was obtained. The conditions of existing cable lines show that replacement is necessary. Otherwise, the fault situation would happen. In this case company would loss not only money but also its prestige. As a solution, XLPE single core cables are more profitable than other types of cable considered in this work. Moreover, it is presented the dependence of value of short circuit current on number of 10/110 kV transformers connected in parallel between main grid and considered 10 kV busbar and how it affects on final decision. Furthermore, the losses of company in power (capacity) market due to fault situation are presented. These losses are commensurable with investment to replace existing cable system.

Estimation of standard enthalpy of formation of alkanes in gaseous state by calculating size, structural and electronic parameters in the molecules

A quantitative analysis is made on the correlation ship of thermodynamic property, i.e., standard enthalpy of formation (ΔH fº) with Kier's molecular connectivity index(¹Xv),vander waal's volume (Vw) electrotopological state index (E) and refractotopological state index (R) in gaseous state of alkanes. The regression analysis reveals a significant linear correlation of standard enthalpy of formation (ΔH fº) with ¹Xv, Vw, E and R. The equations obtained by regression analysis may be used to estimate standard enthalpy of formation (ΔH fº) of alkanes in gaseous state.

Estimation of the potential evapotranspiration by a simplified penman method

The numerous methods for calculating the potential or reference evapotranspiration (ETo or ETP) almost always do for a 24-hour period, including values of climatic parameters throughout the nocturnal period (daily averages). These results have a nil effect on transpiration, constituting the main evaporative demand process in cases of localized irrigation. The aim of the current manuscript was to come up with a model rather simplified for the calculation of diurnal daily ETo. It deals with an alternative approach based on the theoretical background of the Penman method without having to consider values of aerodynamic conductance of latent and sensible heat fluxes, as well as data of wind speed and relative humidity of the air. The comparison between the diurnal values of ETo measured in weighing lysimeters with elevated precision and estimated by either the Penman-Monteith method or the Simplified-Penman approach in study also points out a fairly consistent agreement among the potential demand calculation criteria. The Simplified-Penman approach was a feasible alternative to estimate ETo under the local meteorological conditions of two field trials. With the availability of the input data required, such a method could be employed in other climatic regions for scheduling irrigation.

Estimation of transpiration of the 'Valencia' orange young plant using thermal dissipation probe method

Most studies on measures of transpiration of plants, especially woody fruit, relies on methods of heat supply in the trunk. This study aimed to calibrate the Thermal Dissipation Probe Method (TDP) to estimate the transpiration, study the effects of natural thermal gradients and determine the relation between outside diameter and area of xylem in 'Valencia' orange young plants. TDP were installed in 40 orange plants of 15 months old, planted in boxes of 500 L, in a greenhouse. It was tested the correction of the natural thermal differences (DTN) for the estimation based on two unheated probes. The area of the conductive section was related to the outside diameter of the stem by means of polynomial regression. The equation for estimation of sap flow was calibrated having as standard lysimeter measures of a representative plant. The angular coefficient of the equation for estimating sap flow was adjusted by minimizing the absolute deviation between the sap flow and daily transpiration measured by lysimeter. Based on these results, it was concluded that the method of TDP, adjusting the original calibration and correction of the DTN, was effective in transpiration assessment.