Blade pitch control malfunction simulation in a wind energy conversion system with MPC five-level converter

This paper is on a wind energy conversion system simulation of a transient analysis due to a blade pitch control malfunction. The aim of the transient analysis is the study of the behavior of a back-to-back multiple point clamped five-level full-power converter implemented in a wind energy conversion system equipped with a permanent magnet synchronous generator. An alternate current link connects the system to the grid. The drive train is modeled by a three-mass model in order to simulate the dynamic effect of the wind on the tower. The control strategy is based on fractional-order control. Unbalance voltages in the DC-link capacitors are lessen due to the control strategy, balancing the capacitor banks voltages by a selection of the output voltage vectors. Simulation studies are carried out to evaluate not only the system behavior, but also the quality of the energy injected into the electric grid.

Power converters in WBG device technology for automotive applications and characterization setups for GaN power transistors

This PhD dissertation envisages the design of innovative power converters exploiting WBG devices to get state-of-the-art performance in products intended for industrial applications of automotive field. The collaborations with different specialized companies, provided the opportunity to access commercially-available state-of-the-art SiC and GaN technologies and the possibility to realize innovative converter prototypes. Concerning SiC technology, the complete design of a $350kW$ Battery Emulator instrument in collaboration with a company leader in the automotive testing sector, was carried out from scratch exploiting state-of-the-art SiC power-modules, planar magnetics and top-notch MCU technologies. Discrete high-voltage GaN switches were exploited in the Power Supplies design for automotive charger application to target improved performances compared to the market state-of-the-art. Specifically, two high-efficiency prototypes, an AC/DC converter and a DC/DC converter of $7.5kW$, have been realized for this purpose. To further investigate the characteristics of state-of-the-art GaN power devices two measurement set-ups have been designed. In particular, the trapping phenomenon causing the collapse of drain current during ON-state with a consequent degradation of ON-resistance has been analyzed.

Modellazione, controllo e sviluppo sperimentale di un azionamento con convertitore boost integrato per DC fast charge

La presente trattazione propone un metodo innovativo per la fast DC charge, che permette di collegare le colonnine di ricarica a 400 V ai veicoli con batteria ad 800 V. Il collegamento avviene tramite l���azionamento elettrico di propulsione, che deve dunque essere riconfigurato durante la ricarica sotto forma di ���integrated boost DC/DC converter���. L'elaborato illustra il modello matematico del sistema, lo schema di controllo in ambiente Simulink ed i risultati delle simulazioni. Infine, sono illustrate le prove a banco effettuate sul sistema in esame, la strumentazione utilizzata ed i risultati ottenuti per le configurazioni confrontate. Tuttavia, si dimostra che il metodo di ricarica richiede un���ulteriore induttanza per il collegamento al motore per evitare gli elevati ripple delle correnti di fase ed il conseguente surriscaldamento dei magneti rinvenuto durante le prove sperimentali.

Analisi fem, simulazione e sperimentazione di un azionamento brushless con convertitore boost integrato per DC fast charge

L'elaborato analizza il funzionamento di un integrated boost converter, operante come sistema di interfaccia per la ricarica di un veicolo elettrico operante a 800V con la colonnina di ricarica a 400V. Il convertitore utilizza le fasi dell'azionamento di trazione come induttanze di filtro. Mediante un���analisi agli elementi finiti sono stati estratti i parametri del motore elettrico di un veicolo stradale operante a 800V. Il funzionamento del convertitore �� studiato in ciascuna delle configurazioni proposte in ambiente Simulink. Poi, sono state individuate le posizioni che permettono il funzionamento ottimale del sistema ed infine sono state eseguite le prove a banco per verificare le previsioni dei modelli matematici dell'integrated boost converter. Si �� quindi ottenuta una configurazione dell'azionamento a bordo del veicolo che permette il trasferimento di energia tra batteria e colonnina di ricarica a tensione inferiore, seppur siano richiesti sviluppi futuri per poter avere una ricarica completa della batteria.

Studio e implementazione del processo di polarizzazione in AC su materiali piezoelettrici nanofibrosi

I materiali piezoelettrici sono una classe di materiali che hanno la capacit�� di convertire energia elettrica in meccanica, e viceversa. I piezoelettrici si suddividono in tre classi: naturarli, ceramici e polimerici. Quest'ultimi, seppur mostrando coefficienti piezoelettrici non elevati rispetto ai primi due, presentano grandi vantaggi in termini di propriet�� meccaniche, essendo per esempio molto flessibili, grazie anche all'ausilio delle nanotecnologie. In questo elaborato si �� utilizzato il PVDF-TrFE, un materiale polimerico, prodotto sotto forma di nanofibre tramite il processo di elettrofilatura. La struttura nanofibrosa incrementa le propriet�� piezoelettriche, che dipendono dalla superficie totale del materiale, poich�� massimizza il rapporto superficie/volume. Lo scopo dell'elaborato �� quello di ottimizzare il processo di polarizzazione, e quindi incrementare la risposta elettromeccanica dei provini a seguito di una sollecitazione, applicando una tecnica innovativa. Questa prevede l'applicazione di un campo elettrico AC sinusoidale, partendo da un valor nullo fino a un valore massimo di regime, continuando successivamente con un campo in DC avente la stessa apiezza massima. Questa tecnica �� stata applicata a differenti provini di PVDF-TrFE, variando alcuni parametri come frequenza, numero di cicli e temperatura. I valori misurati sono stati suddivisi in diversi grafici al variare della temperatura, mostrando notevoli miglioramenti rispetto alle tecniche gi�� note di polarizzazione. �� stata inoltre mostrata la struttura in scala nanometrica delle fibre, valutando cos�� l'effetto della temperatura di esercizio sui provini durante il processo di polarizzazione.

Design and implementation of a synchronous interleaved boost converter for fuel cell-powered catamaran

The present work describes the different stages of design, implementation, and validation procedures for an interleaved DC-DC boost converter intended for the 2022 Futura, a fuel cell-powered racing catamaran developed by the UniBoAT team. The main goal of the entire design has been the significant reduction of the weight of the converter by removing heat sinks and reducing component size while increasing its efficiency by adopting high-end power switches and the interleaved architecture operated with a synchronous control strategy. The obtained converter has been integrated into the structure containing the fuel cell stack obtaining a fully integrated system. The realized device has been based on an interleaved architecture with six phases controlled digitally through the average current mode control. The design has been validated through simulations carried out using the software LT-Spice, whereas experimental validations have been performed by means of laboratory bench tests and on-field tests. Detailed thermal and efficiency analyses are provided with the bench tests under the two synchronous and non-synchronous operating modes and with the adoption of the phase shedding technique. The prototype implementation and its performance in real operating conditions are also discussed. Eventually, it is underlined as the designed converter can be used in other applications requiring a voltage-controlled boost converter.

N��mero cromoss��mico em esp��cies brasileiras de Adesmia DC. (Leguminosae-Faboideae)

Chromosome numbers of 11 South-Brazilian species of Adesmia were determined. The cytological preparations were obtained by squashing cells of root tips, using the acetic-orcein method. The chromosome number for all the species studied was 2n=20, excepting A. incana var. incana with 2n=ca.40. The counts are new for nine species, and the other two agree with the literature. It is suggested x=10 as the basic number for the genus. Up to the present only four species were cited as polyploid.

Educa����o fisica na educa����o infantil : a realidade nas secretarias municipais de educa����o de Belem-PA, Macapa-AP, Palmas-TO e Rio Branco-AC

Universidade Estadual de Campinas . Faculdade de Educa����o F��sica

Tracking dos indicadores da aptid��o fisica relacionada a saude em escolares

Universidade Estadual de Campinas . Faculdade de Educa����o F��sica

Anatomia foliar de Eugenia florida DC. (Myrtaceae)

Foi feito o estudo anat��mico da folha de Eugenia florida DC., esp��cie arb��rea da fam��lia Myrtaceae, coletada no Campus da Funda����o Oswaldo Cruz, Rio de Janeiro, RJ. A esp��cie apresenta importantes propriedades farmacol��gicas, incluindo-se atividade antiviral. O presente estudo teve como objetivo fornecer dados, revelados atrav��s da microscopia ��ptica e da microscopia eletr��nica de varredura, que possam contribuir para o conhecimento da esp��cie e, conseq��entemente, para a seguran��a em sua identifica����o. Anatomicamente, a folha �� hipostom��tica, com organiza����o dorsiventral do mesofilo. Apresenta tricomas simples apenas sobre a nervura mediana da face adaxial. As c��lulas epid��rmicas apresentam contorno sinuoso em vista frontal e cut��cula estriada. O par��nquima pali����dico destaca-se pela grande quantidade de cristais prism��ticos de oxalato de c��lcio. Em posi����o subepid��rmica ocorrem cavidades secretoras de ��leos essenciais, pouco numerosas, nas duas faces da l��mina foliar. As c��lulas epid��rmicas situadas sobre as estruturas secretoras constituem caracter��stica de valor diagn��stico e s��o reconhec��veis pela c��lula de topo, que �� reniforme, circundada pelas adjacentes, que apresentam disposi����o radiada. A compara����o entre folhas de sol e de sombra revela que, nas primeiras, as estruturas secretoras s��o completamente diferenciadas, ao contr��rio das folhas de sombra, al��m de apresentarem maior concentra����o de compostos erg��sticos.

Morfo-anatomia foliar de Myrcia multiflora (Lam.) DC. - Myrtaceae

Folhas de Myrcia multiflora (Lam.) DC. s��o usadas na medicina popular como hipoglicemiantes. O objetivo deste trabalho foi caracterizar morfol��gica e anatomicamente as folhas desta planta, de modo que os dados obtidos possam ser utilizados como refer��ncia em exames de controle de qualidade de amostras de f��rmacos, com vistas a verificar a autenticidade. Folhas inteiras foram diafanizadas e coradas para o estudo da nerva����o. Sec����es transversais do pec��olo e transversais e parad��rmicas da l��mina foliar foram analisadas em microsc��pio ��ptico (MO) e a superf��cie do limbo foi observada, tamb��m, em microscopia eletr��nica de varredura (MEV). Foram aplicados testes histoqu��micos em material fresco, para identifica����o e localiza����o de glic��dios, amido, taninos, lignina, cristais e s��lica. Morfologicamente, a folha �� simples, oval-el��ptica, com margem inteira, base aguda, ��pice acuminado e textura cart��cea. A vena����o �� do tipo campt��dromo-broquid��dromo. Anatomicamente, a folha �� hipostom��tica, com mesofilo compacto e dorsiventral, com tr��s estratos de par��nquima pali����dico. A epiderme �� uniestratificada, silicificada em algumas regi��es e as c��lulas exibem paredes anticlinais retas. Em posi����o subepid��rmica ocorrem numerosas cavidades secretoras de ��leos essenciais. Os feixes vasculares s��o colaterais e acompanhados por s��ries cristal��feras. Os dados obtidos s��o comparados com os de outras esp��cies de Myrtaceae e conclui-se que as caracter��sticas morfol��gicas e anat��micas de M. multiflora contribuem para a diagnose.

An AC-5 cathepsin B-like protease purified from Haemonchus contortus excretory secretory products shows protective antigen potential for lambs

The immunogenic properties of cysteine proteases obtained from excretory/secretory products (ES) of Haemonchus contortus were investigated with a fraction purified with a recombinant H. contortus cystatin affinity column. The enrichment of H. contortus ES for cysteine protease was confirmed with substrate SDS-PAGE gels since the cystatin-binding fraction activity was three times higher than total ES, despite representing only 3% of total ES. This activity was inhibited by a specific cysteine protease inhibitor (E64) and by recombinant cystatin. The one-dimensional profile of the cystatin-binding fraction displayed a single band with a molecular mass of 43 kDa. Mass spectrometry showed this to be AC-5, a cathepsin B-like cysteine protease which had not been identified in ES products of H. contortus before. The cystatin binding fraction was tested as an immunogen in lambs which were vaccinated three times (week 0, 2.5 and 5), challenged with 10 000 L3 H. contortus (week 6) before necropsy and compared to unvaccinated challenge controls and another group given total ES (n = 10 per group). The group vaccinated with cystatin-binding proteins showed 36% and 32% mean worm burden and eggs per gram of faeces (EPG) reductions, respectively, compared to the controls but total ES was almost without effect. After challenge the cystatin-binding proteins induced significantly higher local and systemic ES specific IgA and IgG responses.

Theory of small-signal ac response of a dielectric liquid containing two groups of ions

The analysis of Macdonald for electrolytes is generalized to the case in which two groups of ions are present. We assume that the electrolyte can be considered as a dispersion of ions in a dielectric liquid, and that the ionic recombination can be neglected. We present the differential equations governing the ionic redistribution when the liquid is subjected to an external electric field, describing the simultaneous diffusion of the two groups of ions in the presence of their own space charge fields. We investigate the influence of the ions on the impedance spectroscopy of an electrolytic cell. In the analysis, we assume that each group of ions have equal mobility, the electrodes perfectly block and that the adsorption phenomena can be neglected. In this framework, it is shown that the real part of the electrical impedance of the cell has a frequency dependence presenting two plateaux, related to a type of ambipolar and free diffusion coefficients. The importance of the considered problem on the ionic characterization performed by means of the impedance spectroscopy technique was discussed. (c) 2008 American Institute of Physics.

Effect of weak dipolar interaction on the magnetic properties of Ni nanoparticles assembly analyzed with different protocols

The effect of weak dipolar interactions (DIs) between Ni nanoparticles (NPs) in samples with different Ni concentrations was investigated by performing a detailed characterization of their structural and magnetic properties. From the determination of several physical parameters of Ni NP assemblies, it was found that the ac and dc magnetic susceptibility measurements are valuable for identifying the DIs between NPs while hysteresis loops measurements showed to be very insensitive, provided that the strength of the DI field is much smaller than the maximum coercive field. Therefore, the sensitivity of the observed static and dynamical magnetic properties to the effect of weak DI depends on the measurement protocols used. (C) 2011 American Institute of Physics. [doi:10.1063/1.3556767]

Partial magnetic ordering and crystal structure of the ludwigites Co(2)FeO(2)BO(3) and Ni(2)FeO(2)BO(3)

We present an extensive study of the structural, magnetic, and thermodynamic properties of the two heterometallic oxyborates: Co(2)FeO(2)BO(3) and Ni(2)FeO(2)BO(3). This has been carried out through x-ray diffraction at room temperature (RT) and 150 K, dc and ac magnetic susceptibilities, and specific-heat experiments in single crystals above 2 K. The magnetic properties of these iron ludwigites are discussed in comparison with those of the other two known homometallic ludwigites: Fe(3)O(2)BO(3) and Co(3)O(2)BO(3). In both ludwigites now studied we have found that the magnetic ordering of the Fe(3+) ions occurs at temperatures very near to which they order in Fe(3)O(2)BO(3). A freezing of the divalent ions (Co and Ni) is observed at lower temperatures. Our x-ray diffraction study of both ludwigites at RT and 150 K showed very small ionic disorder in apparent contrast with the freezing of the divalent ion spins. The structural transition that occurs in homometallic Fe(3)O(2)BO(3) has not been found in the present mixed ludwigites in the temperature range investigated.