Project of a bandgap voltage reference and a temperature sensor for "energy harvest" systems

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e Computadores

Application of NMR RDC’s, relaxation and self-diffusion for the study of dynamic processes of small molecules in solution

Spin-lattice Relaxation, self-Diffusion coefficients and Residual Dipolar Couplings (RDC’s) are the basis of well established Nuclear Magnetic Resonance techniques for the physicochemical study of small molecules (typically organic compounds and natural products with MW < 1000 Da), as they proved to be a powerful and complementary source of information about structural dynamic processes in solution. The work developed in this thesis consists in the application of the earlier-mentioned NMR techniques to explore, analyze and systematize patterns of the molecular dynamic behavior of selected small molecules in particular experimental conditions. Two systems were chosen to investigate molecular dynamic behavior by these techniques: the dynamics of ion-pair formation and ion interaction in ionic liquids (IL) and the dynamics of molecular reorientation when molecules are placed in oriented phases (alignment media). The application of NMR spin-lattice relaxation and self-diffusion measurements was applied to study the rotational and translational molecular dynamics of the IL: 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4]. The study of the cation-anion dynamics in neat and IL-water mixtures was systematically investigated by a combination of multinuclear NMR relaxation techniques with diffusion data (using by H1, C13 and F19 NMR spectroscopy). Spin-lattice relaxation time (T1), self-diffusion coefficients and nuclear Overhauser effect experiments were combined to determine the conditions that favor the formation of long lived [BMIM][BF4] ion-pairs in water. For this purpose and using the self-diffusion coefficients of cation and anion as a probe, different IL-water compositions were screened (from neat IL to infinite dilution) to find the conditions where both cation and anion present equal diffusion coefficients (8% water fraction at 25 ºC). This condition as well as the neat IL and the infinite dilution were then further studied by 13C NMR relaxation in order to determine correlation times (c) for the molecular reorientational motion using a mathematical iterative procedure and experimental data obtained in a temperature range between 273 and 353 K. The behavior of self-diffusion and relaxation data obtained in our experiments point at the combining parameters of molar fraction 8 % and temperature 298 K as the most favorable condition for the formation of long lived ion-pairs. When molecules are subjected to soft anisotropic motion by being placed in some special media, Residual Dipolar Couplings (RDCs), can be measured, because of the partial alignment induced by this media. RDCs are emerging as a powerful routine tool employed in conformational analysis, as it complements and even outperforms the approaches based on the classical NMR NOE or J3 couplings. In this work, three different alignment media have been characterized and evaluated in terms of integrity using 2H and 1H 1D-NMR spectroscopy, namely the stretched and compressed gel PMMA, and the lyotropic liquid crystals CpCl/n-hexanol/brine and cromolyn/water. The influence that different media and degrees of alignment have on the dynamic properties of several molecules was explored. Different sized sugars were used and their self-diffusion was determined as well as conformation features using RDCs. The results obtained indicate that no influence is felt by the small molecules diffusion and conformational features studied within the alignment degree range studied, which was the 3, 5 and 6 % CpCl/n-hexanol/brine for diffusion, and 5 and 7.5 % CpCl/n-hexanol/brine for conformation. It was also possible to determine that the small molecules diffusion verified in the alignment media presented close values to the ones observed in water, reinforcing the idea of no conditioning of molecular properties in such media.

The spin-off of Sonae Capital

The purpose of this project is to study the spin-off of Sonae Capital, which took place in January 2008. Taking the form of a case study, this project is divided between the case narrative and a teaching note. I study the background and motivation of the transaction, along with its outcome. With the available information at the time of the case, I value Sonae Capital at the date of the spin-off and describe a possible trading strategy involving both the spun-off and the demerged companies. Finally, I conclude that the transaction was more beneficial for the parent company, Sonae SGPS, and that it did not follow the typical outperformance pattern observed in other spin-offs.

Study of AC losses in medium-sized high temperature superconducting coils

The study of AC losses in superconducting pancake coils is of utmost importance for the development of superconducting devices. Due to different technical difficulties this study is usually performed considering one of two approaches: considering superconducting coils of few turns and studying AC losses in a large frequency range vs. superconducting coils with a large number of turns but measuring AC losses only in low frequencies. In this work, a study of AC losses in 128 turn superconducting coils is performed, considering frequencies ranging from 50 Hz till 1152 Hz and currents ranging from zero till the critical current of the coils. Moreover, the study of AC losses considering two different simultaneous harmonic components is also performed and results are compared to the behaviour presented by the coils when operating in a single frequency regime. Different electrical methods are used to verify the total amount of AC losses in the coil and a simple calorimetric method is presented, in order to measure AC losses in a multi-harmonic context. Different analytical and numerical methods are implemented and/or used, to design the superconducting coils and to compute the total amount of AC losses in the superconducting system and a comparison is performed to verify the advantages and drawbacks of each method.

Introducing spin-off stocks into the NSP’s risk parity strategy

Field lab: Nova Student Portfolio

Carl Icahn pushes ebay to spin-off paypal

The following case-study describes the situation involving eBay, PayPal and Carl Icahn as of February 2014. Its structure is divided between the narrative and a teaching note. The case narrative describes all the events between the three parties until the 24th of February 2014, when the activist investor Carl Icahn sends a public shareholder letter strongly criticizing eBay’s board and corporate governance practices while proposing at the same time the spin-off of PayPal from eBay. The teaching note intends to analyse the possibility of spinning-off PayPal, while at the same time analysing the Corporate Governance issues in eBay’s board. The final conclusion in the teaching note is favourable towards the spin-off of PayPal.

Assessment of NDVI, land surface temperature and precipitation anomalies for drought monitoring in Bayankhongor province, Mongolia

During the last decade Mongolia’s region was characterized by a rapid increase of both severity and frequency of drought events, leading to pasture reduction. Drought monitoring and assessment plays an important role in the region’s early warning systems as a way to mitigate the negative impacts in social, economic and environmental sectors. Nowadays it is possible to access information related to the hydrologic cycle through remote sensing, which provides a continuous monitoring of variables over very large areas where the weather stations are sparse. The present thesis aimed to explore the possibility of using NDVI as a potential drought indicator by studying anomaly patterns and correlations with other two climate variables, LST and precipitation. The study covered the growing season (March to September) of a fifteen year period, between 2000 and 2014, for Bayankhongor province in southwest Mongolia. The datasets used were MODIS NDVI, LST and TRMM Precipitation, which processing and analysis was supported by QGIS software and Python programming language. Monthly anomaly correlations between NDVI-LST and NDVI-Precipitation were generated as well as temporal correlations for the growing season for known drought years (2001, 2002 and 2009). The results show that the three variables follow a seasonal pattern expected for a northern hemisphere region, with occurrence of the rainy season in the summer months. The values of both NDVI and precipitation are remarkably low while LST values are high, which is explained by the region’s climate and ecosystems. The NDVI average, generally, reached higher values with high precipitation values and low LST values. The year of 2001 was the driest year of the time-series, while 2003 was the wet year with healthier vegetation. Monthly correlations registered weak results with low significance, with exception of NDVI-LST and NDVI-Precipitation correlations for June, July and August of 2002. The temporal correlations for the growing season also revealed weak results. The overall relationship between the variables anomalies showed weak correlation results with low significance, which suggests that an accurate answer for predicting drought using the relation between NDVI, LST and Precipitation cannot be given. Additional research should take place in order to achieve more conclusive results. However the NDVI anomaly images show that NDVI is a suitable drought index for Bayankhongor province.