Modelling and optimisation of magnetic circuits for next generation Hall-effect thrusters

Within electric propulsion, Hall-effect thrusters are an attractive alternative to chemical propulsion for low-thrust applications. The applied magnetic field in Hall thrusters is a relevant part of the design process, on which studies are conducted for erosion reduction, among others. The present thesis is focused on the magnetic topology of next generation Hall-effect thrusters. A magnetostatics simulation tool for axisymmetric problems is developed on the basis of the Finite Element Method Magnetics solver, with which it is possible to attain different topographies, as the so known as singular-point and, within Erosion Reduction Strategies (ERS), the magnetic shielding. In addition, the tool allows for the launching of several simulations in series (a batch), in which different parameters may be modified from one case to the next. In the line of the development of magnetic circuits, a parametric study on coil design is performed, revealing the parameters necessary to fulfil geometric and electric current constraints on coils. The analysis allows for the design of a circuit feasible to be manufactured if properly translated from the axisymmetric model to a three-dimensional geometry, furthermore with the possibility of mass or power optimisation. Finally, a scaling process on the basis of an existing device is performed to design a low-power Hall thruster, of which main design parameters, and, building on them, a suitable magnetic circuit, are obtained.Grado en Ingeniería Aeroespacia

Estudio del control de la respiración y de la disnea fisiológica durante el embarazo

Tesis doctoral inédita. Universidad Autónoma de Madrid. Facultad de Medicina, Departamento de Medicina. Fecha de lectura: 28-10-9

Epidemiological and pathogenic relationship between sleep apnea and ischemic heart disease

Obstructive sleep apnea is recognized as having high prevalence and causing remarkable cardiovascular risk. Coronary artery disease has been associated with obstructive sleep apnea in many reports. The pathophysiology of coronary artery disease in obstructive sleep apnea patients probably includes the activation of multiple mechanisms, as the sympathetic activity, endothelial dysfunction, atherosclerosis, and systemic hypertension. Moreover, chronic intermittent hypoxia and oxidative stress have an important role in the pathogenesis of coronary disease and are also fundamental to the development of atherosclerosis and other comorbidities present in coronary artery diseases such as lipid metabolic disorders. Interestingly, the prognosis of patients with coronary artery disease has been associated with obstructive sleep apnea and the severity of sleep disordered breathing may have a direct relationship with the morbidity and mortality of patients with coronary diseases. Nevertheless, treatment with CPAP may have important effects, and recent reports have described the benefits of obstructive sleep apnea treatment on the recurrence of acute heart ischaemic events in patients with coronary artery diseas

Kinetic study of an autocatalytic reaction: nitrosation of formamidine disulfide

The reaction kinetics for the acid nitrosation of formamidine disulfide (FDS) show an autocatalytic behavior that arises from the fact that the thiocyanate ion formed as a product acts as a powerful catalyst for the nitrosation reaction. In the presence of added nucleophiles the suppression of the autocatalytic route results from competition for the nitrous acid between the added halides and the thiocyanate anion, which is formed as a reaction product. Analysis of the kinetic data enabled extraction of the bimolecular rate constants, kNO+ = (3.2 1.8) 1010 M 1 s 1; kNOSCN = (2.1 0.2) 105 M 1 s 1; kNOBr = (9.4 0.2) 106 M 1 s1 and kNOCl = (4.0 0.2) 107 M 1 s 1, for the pathways catalyzed by SCN , Br and Cl , respectively. Kinetic results are consistent with the attack on the nitrosating agent as the rate limiting step, i.e., the nitrosation of FDS behaves in a similar manner to the nitrosation of an amine. Rather different behavior is found for other substrates with an imino moiety adjacent to an amino nitrogen, such as the guanidines, which react by a mechanism in which the rate limiting step is the reorganization of the nitrosated substrate

Smart Roads Classification

[EN] This article is based on the PIARC Special Project "Smart Roads Classification" which was funded by PIARC with financial support from Spain, Belgium, Canada-Québec and the USA. The project was carried out by a team from the Universitat Politècnica de València (UPV, Spain) with the support of PIARC General Secretariat and of an Oversight Team from different countries. The full Report can be found in the special projects section of PIARC¿s website.García García, A.; Camacho-Torregrosa, FJ.; Llopis-Castelló, D.; Monserrat Del Río, JF. (2021). Smart Roads Classification. Routes - Roads. (391):23-27. http://hdl.handle.net/10251/189900232739

Considerations on the physical and mechanical properties of lime-stabilized rammed earth walls and their evaluation by ultrasonic pulse velocity testing

This study examines the influence of moulding moisture content on the compressive strength, dry density and porosity of a rammed earth wall, using ultrasound as a complementary technique. Non-parametric and multivariate statistical techniques were applied to analyse the behaviour of variables with a sufficiently large population. The statistical analysis demonstrated that excessive or insufficient moulding moisture content directly determines the physical-mechanical properties of such walls. Ultrasound was confirmed as a valid technique for assessing the quality of a wall, since its response, albeit with certain limitations, was consistent with physical-mechanical properties

Multilayer hazes over Saturn’s hexagon from Cassini ISS limb images

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A new insight on the decreasing sea level trend over the Ionian basin in the last decades

Se adjunta la versión postprint aceptada, que incluye las correcciones de de los revisores, debido a que la editorial tiene los derechos de copyright y no permite la difusión en acceso abierto de la versión publicada. Puede accederse a la misma a través del DOI que se incluye en los datos de la publicación.Altimetry measurements over the Ionian region and tide gauge records along the southern Italian coasts have been combined to analyse the negative sea level trend over the Ionian basin in the last decades. The apparent decreasing trend should be better understood as an abrupt sea level drop in 1998 probably linked to changes in the surface circulation in the Ionian basin induced by the Eastern Mediterranean Transient, which changed from anticyclonic to cyclonic about March 1998. From then onwards, a rising rate of 7.9 ± 0.9 mm/year is observed over the basin.Este trabajo se llevó a cabo en el marco del proyecto P07-RNM-02938 financiado por la Junta de Andalucía. También tuvo financiación parcial del proyecto CTM2006-02326 financiado por Ministerio de Ciencia y Tecnología de España. JSN disfrutaba de una beca de doctorado de la Conserjería de Innovación Ciencia y Empresa, Junta de Andalucía

Creating and Validating the DESEA Questionnaire for Men and Women

In clinical practice, it is essential to be able to identify hypoactive sexual desire disorder (HSDD), with its different severity levels and assess the influence the subject's relationship has on the issue. In order to do this, questionnaires are needed that comprise appropriate psychometric properties. We analyzed the psychometric properties and factorial structure of the Sexual Desire and Aversion (DESEA) questionnaire that evaluates sexual desire and interpersonal stress (relationship problems) in male and female couples. A pilot study was conducted with a group of 1583 people. Finally, it included 20,424 Spanish speakers who answered the questionnaire via an online link. The requirements for factor analysis were verified followed by the exploratory and confirmatory factor analysis. The Cronbach's alpha coefficient calculated the reliability of the test scores at 0.834 in the pilot group and 0.889 in the final group. A 3-factor factorial design explains the 62.08% variance. The KMO (Kaiser-Meyer-Olkin) test (p= 0.904), Bartlett's test of sphericity (126,115.3;p= 0.000010) and the matrix determinant (0.0020770) verified the appropriateness of the factor analysis. The results show that the DESEA questionnaire is a reliable and valid instrument for evaluating desire and interpersonal stress, both in women and men, in clinical and research contexts