Modular multilevel converter losses model for HVdc applications

Multi-terminal high voltage dc (HVdc) grids can eventually became a feasible solution to transport energy to remote and/ or distant areas and its exploitation depend, among other things, on the performance of the converter terminals. Therefore, to optimize the power transmission strategy along such a grid, it is necessary to recognize the efficiency of all the converters in all points of operation, namely with the different load conditions. In this vision, the aim of this work is to provide the methodology to model the modular multilevel converter (MMC) efficiency by means of a mathematical expression that can describe, over a broad range of active and reactive power flow combinations, the power losses generated by the semiconductors. According to the presented methodology, a polynomial-based model with a reduced number of coefficients is deducted, in such a way that can be directly used for optimal power flow (OPF) studies. The accuracy of the proposed model is characterized by an absolute relative error, at the worst scenario, approximately equal to 3%.Postprint (author's final draft

On the chemical composition of Titan's dry lakebed evaporites

Titan, the main satellite of Saturn, has an active cycle of methane in its troposphere. Among other evidence for a mechanism of evaporation at work on the ground, dry lakebeds have been discovered. Recent Cassini infrared observations of these empty lakes have revealed a surface composition poor in water ice compared to that of the surrounding terrains --- suggesting the existence of organic evaporites deposits. The chemical composition of these possible evaporites is unknown. In this paper, we study evaporite composition using a model that treats both organic solids dissolution and solvent evaporation. Our results suggest the possibility of large abundances of butane and acetylene in the lake evaporites. However, due to uncertainties of the employed theory, these determinations have to be confirmed by laboratory experiments.Comment: Icarus, in pres

A full one-loop charge symmetry breaking effective potential

We calculate the one-loop contributions to the effective potential for the minimal supersymmetric model when scalar fields other than the Higgses have vacuum expectation values. The importance of these contributions for studies of charge and colour breaking bounds is discussed.Comment: 11 pages, 2 figure

Neutral minima in two-Higgs doublet models

We study the neutral minima of two-Higgs doublet models, showing that these potentials can have at least two such minima with different depths. We analyse the phenomenology of these minima for the several types of two-Higgs doublet potentials, where CP is explicitly broken, spontaneously broken or preserved. We discover that it is possible to have a neutral minimum in these potentials where the masses of the known particles have their standard values, with another deeper minimum where those same particles acquire different masses.Comment: 20 pages, 3 figure

Infra-red stability of Yukawa and soft-breaking fixed points

We investigate the infra-red stability of the fixed points in the evolution of the Yukawa couplings, $A$-parameters and soft scalar masses in a broad class of supersymmetric theories. We show that the issue of stability is essentially determined in all three cases by the eigenvalues of the same matrix. In a very wide range of physically interesting theories it follows that, in the asymptotically free case, the existence of stable infra-red fixed points for the Yukawa couplings implies stable infra-red fixed points for the $A$-parameters and soft scalar masses.Comment: 12 pages, tex, Uses harvmac (big). Errors corrected in Eqs. (33)-(35), and some references adde

Acting theory as poetic of drama: A study of the emergence of the concept of 'motivated action' in playwriting theory

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Playwriting theory has, from its beginning, been concerned with the search for the essential nature of dramatic writing. Early playwriting treatises (poetics) defined the essential aspects of drama as being the plot (creation of sequences of fictional events), the moral character of its heroes, the idea of enactment, or the rhetorical and lyrical qualities of the text. These categories were kept through later treatises with different emphasis being put on each category. An understanding of drama as a sequence of fictional events (plot) has been central in acting theory. Modern theories and techniques centred on Stanislavsky’s ideas rely heavily on rehearsal methods that carefully establish the sequence of actions of the characters in a play as a result of psychological motivations. This method was described by Stanislavsky in An Actor’s Work on a Role, published in 1938, and is known as the Method of Physical Actions. This thesis reassesses the definition of playwriting as consisting essentially in the creation of a plot populated by suitable characters. Rather than discussing playwriting theory in isolation it attempts a bridge between acting theory and playwriting theory by using the Method of Physical Actions as an equivalent to plot. Acting theory is thus considered as a theoretical justification for the centrality of plot. The method used is hermeneutic — a systematic interpretation of poetics, unveiling in almost an archaeological manner the relevance of the essential definitions of drama, such as character, source, genre, and language to the concept of plot. The chronological path of development of dramatic theories is shown to be gradual: from the strict obedience to the narrative line imposed by the mythic sources, in classical treatises; through to an interest in the lyrical expression of the predicament of specific characters, in neoclassical theory; to an awareness of specific social types in the eighteenth century; and, finally, to the conception of the plot as a product of the mental life of individual characters in modern theory

Modelling the bending behaviour of plain-woven fabric using flat shell element and strain smoothing technique

This paper describes a new approach to improve on modelling the bending behaviour of plain-woven fabric. The four-node flat shell element is developed by incorporating a strain smoothing technique, six degrees of freedom at each node. The material laws for in-plane and out-of-plane behaviors are expressed in terms of orthotropic elastic material. The physical and mechanical parameters of fabric samples are measured using Kawabata Evaluating System for Fabric (KES-F). An improved numerical model with a strain smoothing operation for modelling the bending behaviour of plain-woven fabric is then carried out. The bending behavior of a rectangular plain-woven fabric sheet with clamped edges is simulated.Fundação para a Ciência e a Tecnologia (FCT