Two-dimensional Time-dependent Point Interactions

We study the time-evolution of a quantum particle subjected to time-dependent zero-range forces in two dimensions. After establishing a conceivable ansatz for the solution to the Schr\"{o}dinger equation, we prove that the wave packet time-evolution is completely specified by the solutions of a system of Volterra-type equations -- the {\it charge equations} -- involving the coefficients of the singular part of the wave function, thus extending to the two-dimensional case known results in one and three dimensions.Comment: 17 pages, AMS-LaTex; presentation of the model changed, small changes to Lemma 2.1 and Proposition 2.

GINI DP 2: Are European Social Safety Nets Tight Enough? Coverage and adequacy of minimum income schemes in 14 EU countries

This paper explores and compares the effectiveness of Minimum Income (MI) schemes in protecting persons of working age from poverty in the European Union. Using the European microsimulation model EUROMOD we estimate indicators of coverage and adequacy of MI schemes in 14 EU countries. In terms of coverage, we find that in several countries a significant number of individuals are ineligible for MI even when they fall below a poverty line set at 40 per cent of median income. With respect to adequacy, we show that in certain countries a large fraction of those entitled to MI remain at very low levels of income even when MI benefit is added. Overall, our findings suggest that the clustering of MI schemes in Europe may be more complex than previous literature has hitherto allowed for.

Numerical and experimental investigation for the performance assessment of full electric marine propulsion plant

The advantage of hybrid diesel-electric propulsion is well known in terms of fuel consumption, especially for ships with variegated speed profiles or with different propulsion loads. Nowadays several hybrid configurations are available and in the preliminary design phase, the selection of the best configuration among several options could be a time-consuming task. Therefore, in this paper, a methodology is proposed, based on the main propulsion design parameters, to identify the global ship energy efficiency in function of the operational profile, considering both design and off-design conditions. In order to validate the method, a sea trial campaign has been done and the records have been analyzed. The developed tool helps, during the design phase, to choose the optimal propulsion configuration, number, type, and size, of the main engines and generators. The methodology is used to compare two design solutions, a conventional diesel propulsion and a proposed full electric plant using a \u2018father and son\u2019 power generation

Parametric study of the influence of the wind assisted propulsion on ships

nologies to increase energy efficiency and reduce ship fuel consumption. Several measures have been identified, or even applied, with the potential to achieve substantial fuel consumption and emission reductions, like slow-steaming, bio-fuels, and alternative propulsion technologies. Slow steaming has been already analysed to a great extent, whereas biofuels have raised concerns about environmental impact and availability. Among alternative propulsion technologies, a resurgence in wind-assisted propulsion is observed in recent years, primarily due to its high potential for fuel consumption and emission reduction. Wind power is currently being developed through both conventional sails and modern alternatives. These include Flettner rotors, kites or spinnakers, soft sails, wing sails and wind turbines. In particular, Flettner rotors are rotating cylinders generating lift when immersed in a fluid stream. This paper presents a ship propulsion model study, able to account for the thrust force produced by the rotor accounting for different vessel speed and weather scenario. This paper aims to assess the improvement of the ship’s energy efficiency and optimise the ship operating conditions in terms of daily performance. The result clearly shows the potential reduction achieved in the propeller delivered power given using the rotor as an auxiliary propulsion device

Point interactions in acoustics: one dimensional models

A one dimensional system made up of a compressible fluid and several mechanical oscillators, coupled to the acoustic field in the fluid, is analyzed for different settings of the oscillators array. The dynamical models are formulated in terms of singular perturbations of the decoupled dynamics of the acoustic field and the mechanical oscillators. Detailed spectral properties of the generators of the dynamics are given for each model we consider. In the case of a periodic array of mechanical oscillators it is shown that the energy spectrum presents a band structure.Comment: revised version, 30 pages, 2 figure

Design and Validation of Dynamic Positioning for Marine Systems: a Case Study

The design of a DP-system is a challenging task with several technical fields involved in the problem solution. Numerical simulation is a powerful tool in order to aid the designer during the system development and to speed up the design process. This paper presents the simulation methodology adopted to design and test the dynamic positioning system for a vessel with a standard propulsion configuration. Simulation results and sea trial measurements are compared to illustrate the reliability of the proposed simulation platform

Decay of a Bound State under a Time-Periodic Perturbation: a Toy Case

We study the time evolution of a three dimensional quantum particle, initially in a bound state, under the action of a time-periodic zero range interaction with ``strength'' (\alpha(t)). Under very weak generic conditions on the Fourier coefficients of (\alpha(t)), we prove complete ionization as (t \to \infty). We prove also that, under the same conditions, all the states of the system are scattering states.Comment: LaTeX2e, 15 page

Investigation of asymmetrical shaft power increase during ship maneuvers by means of simulation techniques

Marine propulsion plants can experience large power fluctuations during tight maneuvers, with increases of shaft torque up to and over 100% of the steady values in straight course and considerable asymmetry between internal and external shafts during turning circle. This phenomenon (studied in Viviani et al 2007a and 2007b can be of particular interest for twin screw ships propulsion systems with coupled shaftlines, in which asymmetrical loads can represent a challenge for the whole propulsion system (e.g. unique reduction gear, shaftlines, automation). A joint research has been set up in order to deeply investigate the phenomenon, by means of large scale model testing and related numerical simulations. In the present work, preliminary simulation results with different simplified automation systems and with an automation system more similar to the real one are reported, allowing to get a better insight into this complex problem

Estudio descriptivo -sistémico para conocer la percepción del significado atribuido a la tradición del matrimonio, en la construcción de la pareja en la posmodernidad

Tesis (Psicología)La presente investigación, es un estudio psicosocial que trata sobre las percepciones atribuidas a la tradición del matrimonio, en la construcción de la pareja en la posmodernidad. Nuestro estudio consistió en llevar a cabo entrevistas a parejas heterosexuales chilenas y con contrato matrimonial, para luego realizar un análisis de discurso. Para llegar a esto, previamente se elaboró un marco teórico que responde a una epistemología flexible, la cual permite una revisión de diversas teorías y modelos explicativos. Por ésta razón, se comenzó a profundizar desde un eje temporal en la modernidad y la posmodernidad, siendo ésta última una respuesta a la anterior. Hay un salto epistemológico considerable y entonces el entendimiento acerca del conocimiento cambia la visión del mundo, de los seres humanos y de sus relaciones. Otro apartado no menos importante, fue dedicado al género como una construcción social que se da de manera diversa en los distintos espacios culturales. Estas construcciones sociales acerca del género, van cambiando conforme a los cambios de época, lo que produce una influencia notable en las relaciones entre las personas, especialmente entre hombres y mujeres, y sobretodo en las parejas. Es así como se introduce uno de los acápites centrales de nuestro marco teórico, en el cual se realiza un revisión acabada y precisa sobre los temas de pareja, incluyendo el establecimiento de los primeros vínculos, la intimidad, la sexualidad y por último la pareja como un sistema marital. La metodología utilizada fue sustentada y coherente con la epistemología construccionista. Por lo tanto el tipo de investigación responde a un estudio cualitativo y descriptivo, tomando en cuenta las características propias de esta nueva forma de entender el conocimiento. Por otra parte, la entrevista construida en base a los objetivos fue semiestructurada con el propósito de invitar a los entrevistados a una conversación abierta sobre el tema. El diseño es transversal, ya que las entrevistas se realizaron a cada pareja en un solo momento. Los resultados fueron expuestos según los ejes temáticos encontrados y a partir de esto se realizó un análisis de discurso. Con posterioridad se expusieron las conclusiones y reflexiones que inspiraron dicho estudio como un proceso nuevo de conocimiento