Analisi e ottimizzazione del progetto di uno stadio di conversione a media frequenza per trazione ferroviaria

Il lavoro esposto in questa tesi è consistito in due fasi, la prima, che potremmo chiamare di modellizzazione circuitale, dove si è andati a modellizzare le linee di trazione ferroviaria in AC, gli IGBT, il trasformatore e tutti gli altri blocchi basi necessari al funzionamento. Durante la seconda fase si è simulato effettivamente il circuito di trazione, e lo si è reso conforme alle normative che regolano le interferenze condotte per i sistemi di trazione in AC. Il Controllo implementato sugli IGBT del convertitore DC-DC impone un periodo in cui gli IGBT sono entrambi spenti, questo provoca l’introduzione sulla tensione del carico di componenti frequenziali non volute. Naturalmente il controllo PWM che è stato implementato per gli IGBT dei convertitori 4QC, ha permesso di ottenere risultati conformi con quelli che erano stati prefissati, nulla vieta però in un futuro lavoro, di cercare nuove strategie di controllo ed implementarle nel sistema. Anche perché nell’ultimo capitolo l’ottimizzazione che è stata fatta, è stata quella di ridurre le componenti frequenziali indesiderate immesse sulla linea mediante filtri notch. Questa architettura, invece, può essere implementata avendo costi inferiori, su locomotive che funzionano su sistemi alimentati a 15 kV 16 2/3 Hz

A comprehensive study for the validation of a LC/MS/MS method for the determination of free and total forms of urinary cortisol and its metabolites

Several pathological conditions can be related to the alteration of the urinary levels of cortisol (F) and itsmetabolites. The determination of each of them in the free and free plus conjugated form can provide adeeper insight into the impaired activity of the cortisol metabolism enzymes, thus improving the diag-nosis protocol currently based only on the determination of total amount of urinary cortisol metabolites.In that view, an LC–MS/MS method for the determination of the free and total amount of urinary F, cor-tisone (E), tetrahydrocortisol (THF), allo-tetrahydrocortisol (A-THF) and tetrahydrocortisone (THE) wasthus developed and validated. Deconjugation of glucocorticoids was carried out by enzymatic hydroly-sis. Analytes were extracted by solid phase extraction, separated by liquid chromatography and analyzedvia electro-spray ionization (negative ion mode) triple-quadrupole mass spectrometry in the selectedreaction monitoring mode using a stable isotope-labeled internal standard.Baseline separation for all compounds, in particular the two stereoisomers A-THF and THF, wasobtained. Matrix effects, not reported so far, were observed and minimized for the determination ofurinary free E and THE. Validated range was 0.5–1000 ng/mL for A-THF and THF, 5–800 ng/mL for E andTHE and 1–1000 ng/mL for F, with R2values greater than 0.9981. The LOD and LOQ of the describedmethod ranged from 0.1 to 3.0 ng/mL, while the extraction recoveries resulted close to 100% for all theglucocorticoids determined. Precision and accuracy were well within ±10%. As suggested by the resultsobtained in the preliminary study on polycystic ovary syndrome (PCOS) urine samples, the method canbe used to support clinical diagnosis of pathologies related to cortisol metabolism. In fact, levels of freeand total glucocorticoids in control subjects were in agreement with previously reported data, as well asfree and total A-THF/THF ratio in PCOS patients. Conversely, in the latter free F/E and A-THF + THF/THEratios were lower than in control subjects (P < 0.01), suggesting a possible alteration of 11-HSD1 and11-HSD2 activity, to be further investigated

Synthesis, x-ray structure and anion binding properties of a cryptand-like hybrid calixpyrrole

The novel cryptand in/out-3, containing two tripyrrolemethane units briged by three 1,3- diisopropylidenbenzene arms was readily synthesized by a convergent three-step synthesis. It binds fluoride by inclusion with excellent selectivity with respect to a number of other tested anions. The structure of the free receptor and that of its fluoride complex were investigated in solution by NMR spectroscopy. The solid state X-ray structure of the free cryptand 3 was also determined

Robust constrained model predictive control based on parameter-dependent Lyapunov functions

The problem of robust constrained model predictive control (MPC) of systems with polytopic uncertainties is considered in this paper. New sufficient conditions for the existence of parameter-dependent Lyapunov functions are proposed in terms of linear matrix inequalities (LMIs), which will reduce the conservativeness resulting from using a single Lyapunov function. At each sampling instant, the corresponding parameter-dependent Lyapunov function is an upper bound for a worst-case objective function, which can be minimized using the LMI convex optimization approach. Based on the solution of optimization at each sampling instant, the corresponding state feedback controller is designed, which can guarantee that the resulting closed-loop system is robustly asymptotically stable. In addition, the feedback controller will meet the specifications for systems with input or output constraints, for all admissible time-varying parameter uncertainties. Numerical examples are presented to demonstrate the effectiveness of the proposed techniques

Factoring in the Micro: A Transaction‐Level Dynamic Factor Approach to the Decomposition of Export Volatility

This paper analyzes the export volatility sources estimating a dynamic factor model on transaction-level data. Utilizing an exhaustive dataset of French export transactions from 1993 to 2017, we reconstruct the latent factors space associated with global and destination-specific macroeconomic shocks through a Quasi-Maximum likelihood approach which allows accommodating both the high share of missing values and the high dimensionality of the microeconomic time series. The estimated parameters are then used to derive a volatility decomposition of the aggregate and firm-level export growth rates, highlighting structural spatial patterns and the role of geographical diversification in mitigating export risks

An investigation on drag reduction for axisymmetric bodies

This thesis, carried out in collaboration with the Queen Mary University of London, has the aim of study drag reduction devices for axisymmetric bodies using both experiments on wind tunnel and numerical flow simulations. Models used for wind tunnel experiments were a 4:1 ellipsoid, with the possibility to replace the rear section with a conic boat tail and a 4:1 prolate ellipsoid; this last model was equipped with an internal fan and modified with an intake at the rear for wake aspiration and a conic mid-section in order to perform boundary layer blowing from an annular slot. Results show how the presence of a conic boat tail lead to a reduction of the form drag and boundary layer suction/wake aspiration have great impact on reducing both viscous and form drag. In this latter case it is suggested, as a future development, a study of the ratio between power saved from the drag reduction and power used by active drag reducing device. CFD main result is that the numerical predictions are capable to follow the experimental trend just with K-Omega SST turbulence model

Unique Associations between Insulin-Like Growth Factor Binding Protein-1, Insulin-Like Growth Factor-1 and T Cell Immunoglobulin Mucin 3 in Successful Twin Pregnancies Conceived with Donor Oocytes

Background and Objectives: To investigate if pregnancies conceived using an oocyte donor necessitate an alteration in immune regulation, we compared concentrations of insulin-like growth factor binding protein (IGFBP)-1, insulin-like growth factor (IGF)-1 and T cell immunoglobulin mucin-3 (Tim-3) in women with ongoing successful twin pregnancies conceived spontaneously, using assisted reproductive technologies that utilized homologous oocytes or with donor oocytes. Differences in levels of these immune modulatory proteins may be magnified and easier to detect in twin as compared to singleton pregnancies. Methods: In this prospective study IGFBP-1 and IGF-1 were measured in sera and Tim-3 in lysates of peripheral blood mononuclear cells (PBMCs) by ELISA. Results: Median IGFBP-1 levels were lower in women with donor oocytes (41.4 ng/ml) as compared to those with a spontaneous conception (51.2 ng/mL) or who conceived with various assisted reproduction protocols using homologous oocytes (52.4 ng/mL) (p &lt; 0.001). IGF-1 and Tim-3 levels were comparable in each group. The IGFBP-1 level was inversely correlated to the IGF-1 concentration only in women with donor oocytes (p = 0.032). IGFBP-1 and Tim-3 levels were similarly negatively correlated in the donor oocyte group (p = 0. 012). Women in the assisted reproduction group who conceived following intracytoplasmic sperm injection were the only other group in which IGFBP-1 and Tim-3 were negatively correlated (p = 0.018). Conclusions: Down-regulation of IGFBP-1 production in pregnancies conceived with donor oocytes may reduce the extent of pro-inflammatory immunity and contribute to successful outcome in totally allogeneic pregnancies

Adsorption Technology for PFAS Removal in Water: Comparison between Novel Carbonaceous Materials

PFASs are a variety of ecologically persistent compounds of anthropogenic origin loosely included in many industrial products. In these, the carbon chain can be fully (perfluoroalkyl substances) or partially (polyfluoroalkyl substances) fluorinated. Their ubiquitous presence in many environmental compartments over the years and their long-lasting nature have given rise to concerns about the possible adverse effects of PFASs on ecosystems and human health. Among a number of remediation technologies, adsorption has been demonstrated to be a manageable and cost-effective method for the removal of PFASs in aqueous media. This study tested two novel and eco-friendly adsorbents (pinewood and date seeds biochar) on six different PFASs (PFOS, GenX, PFHxA, PFOA, PFDA, and PFTeDA). Batch sorption tests (24 h) were carried out to evaluate the removal efficiency of each PFAS substance in relation to the two biochars. All samples of liquid phase were analyzed by a developed and then a well-established method: (i) pre-treatment (centrifugation and filtration) and (ii) determination by high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS/MS). The results evidenced a comparable adsorption capacity in both materials but greater in the long-chain PFASs. Such findings may lead to a promising path towards the use of waste-origin materials in the PFAS remediation field