A liberalização do mercado energético e o papel das entidades reguladoras

The liberalisation of the energy market goes back to the 1990s, when it was impelled by the European legislator. Since then, three legislative packages, temporarily successive, were approved. Those packages contained the measures to be implemented in order to deepen the internal energy market. Besides the opening up of several national markets to competition, the European legislator aimed the creation of a real internal energy market within the European Union. The unbundling regime was one of the most important steps with respect to the liberalisation process. The introduction of these rules ensured independence to the various market operators. A real and effective right of choice was granted to the consumers so they may choose their electricity and natural gas supplier. Therefore, the activity of comercialisation is subject to competition. However, some activities of the electricity’s and natural gas’ chain of value, namely the activities of transportation and distribution, were kept under regulation rules. Even though it may seem odd, the assignment of important competences and strong powers to a regulatory authority was essential in order to achieve the liberalisation process’ goals. Electricity and natural gas are essential public goods; therefore the market operators are legally bound to public service obligations, such as the security, the universality and the continuity of the supply. The performance of these obligations may become, in some cases, unprofitable for those operators. For such reason, the protection of the consumers’ rights shall only be properly defended if there is a regulatory authority that monitors the behaviour of the operators and sanctions the failure to comply with the public service obligations. Portugal, as a Member State of the European Union, transposed into the national legal order the European directives concerning the liberalisation process. This transposition has caused radical changes to the electricity and natural gas’ national markets. The Entidade Reguladora dos Serviços Energéticos also suffered various mutations in order to keep up with the regulatory demands regarding the liberalisation process.

On mappings preserving the sharp and star orders

The present paper is devoted to the study of linear maps preserving certain relations, such as the sharp partial order and the star partial order in semisimple Banach algebras and C*-algebras.

Numerical methods in multibody system dynamics

"Series: Solid mechanics and its applications, vol. 226"

Competição entre megaspórios em milho

The experiments reported were started as early as 1933, when indications were found in class material that the factor for small pollen, spl, causes not only differences in the size of pollen grains and in the growth of pollen tubes, but also a competition between megaspores, as first observed by RENNER (1921) in Oenothera. Dr. P. C. MANGELSDORF, who had kindly furnished the original seeds, was informed and the final publication delayed untill his publication in 1940. A further delay was caused by other circunstances. The main reason for the differences of the results obtained by SINGLETON and MANGELSDORF (1940) and those reported here, seems to be the way the material was analysed. I applied methods of a detailed statistical analysis, while MANGELSDORF and SINGLETON analysed pooled data. 1) The data obtained on pollen tube competition indicate .that there is about 3-4% of crossing-over between the su and sp factors in chromosome IV. The elimination is not always complete, but from 0 to 10% of the sp pollen tubes may function, instead of the 50% expected without elimination. These results are, as a whole, in accordance with SINGLETON and MANGELSDORF's data. 2) Female elimination is weaker and transmission determined as between 16 to 49,5%, instead of 50% without competition, the values being calculated by a special formula. 3) The variability of female elimination is partially genotypical, partially phenotypical. The former was shown by the difference in the behavior of the two progenies tested, while the latter was very evident when comparing the upper and lower halves of ears. For some unknown physiological reason, the elimination is generally stronger in the upper than in the lower half of the ear. 4) The female elimination of the sp gene may be caused theoretically, by either of two processes: a simple lethal effect in the female gametophyte or a competition between megaspores. The former would lead not only to the abortion of the individual megaspores, but of the whole uniovulate ovary. In the case of the latter, the abortive megaspore carrying the gene sp will be substituted in each ovule by one of the Sp megaspores and no abortion of ovaries may be observed. My observations are completely in favor of the second explication: a) The ears were as a whole very well filled except for a few incomplete ears which always appear in artificial pollinations. b) Row arrangement was always very regular. c) The number of kernels on ears with elimination is not smaller than in normal ears, but is incidentally higher : with elimnation, in back-crosses 354 kernels and in selfed ears 390 kernels, without elimination 310 kernels per ear. d) There is no correlation between the intensity of elimination and the number of grains in individual ears; the coefficient; of linear correlation, equal to 0,24, is small and insignificant. e) Our results are in complete disagreement whit those reported by SINGLETON and MANGELSDORF (1940). Since these authors present only pooled date, a complete and detailed analysis which may explain the cause of these divergences is impossible.

RECASTING THE ELLIOTT CONJECTURE

Let A be a simple, unital, finite, and exact C*-algebra which absorbs the Jiang-Su algebra Z tensorially. We prove that the Cuntz semigroup of A admits a complete order embedding into an ordered semigroup which is obtained from the Elliott invariant in a functorial manner. We conjecture that this embedding is an isomor phism, and prove the conjecture in several cases. In these same cases - Z-stable algebras all - we prove that the Elliott conjecture in its strongest form is equivalent to a conjecture which appears much weaker. Outside the class of Z-stable C*-algebras, this weaker conjecture has no known counterexamples, and it is plausible that none exist. Thus, we reconcile the still intact principle of Elliott's classification conjecture -that K-theoretic invariants will classify separable and nuclear C*-algebras- with the recent appearance of counterexamples to its strongest concrete form.

Accuracy vs. simplicity: a complex trade-off

Inductive learning aims at finding general rules that hold true in a database. Targeted learning seeks rules for the predictions of the value of a variable based on the values of others, as in the case of linear or non-parametric regression analysis. Non-targeted learning finds regularities without a specific prediction goal. We model the product of non-targeted learning as rules that state that a certain phenomenon never happens, or that certain conditions necessitate another. For all types of rules, there is a trade-off between the rule's accuracy and its simplicity. Thus rule selection can be viewed as a choice problem, among pairs of degree of accuracy and degree of complexity. However, one cannot in general tell what is the feasible set in the accuracy-complexity space. Formally, we show that finding out whether a point belongs to this set is computationally hard. In particular, in the context of linear regression, finding a small set of variables that obtain a certain value of R2 is computationally hard. Computational complexity may explain why a person is not always aware of rules that, if asked, she would find valid. This, in turn, may explain why one can change other people's minds (opinions, beliefs) without providing new information.

Caracteritació de models funcionals d'àmfores romanes mitjançant Finite Element Analysis

Projecte de recerca elaborat a partir d’una estada al Laboratory of Archaeometry del National Centre of Scientific Research “Demokritos” d’Atenes, Grècia, entre juny i setembre 2006. Aquest estudi s’emmarca dins d’un context més ampli d’estudi del canvi tecnològic que es documenta en la producció d’àmfores de tipologia romana durant els segles I aC i I dC en els territoris costaners de Catalunya. Una part d’aquest estudi contempla el càlcul de les propietats mecàniques d’aquestes àmfores i la seva avaluació en funció de la tipologia amforal, a partir de l’Anàlisi d’Elements Finits (AEF). L’AEF és una aproximació numèrica que té el seu origen en les ciències d’enginyeria i que ha estat emprada per estimar el comportament mecànic d’un model en termes, per exemple, de deformació i estrès. Així, un objecte, o millor dit el seu model, es dividit en sub-dominis anomenats elements finits, als quals se’ls atribueixen les propietats mecàniques del material en estudi. Aquests elements finits estan connectats formant una xarxa amb constriccions que pot ser definida. En el cas d’aplicar una força determinada a un model, el comportament de l’objecte pot ser estimat mitjançant el conjunt d’equacions lineals que defineixen el rendiment dels elements finits, proporcionant una bona aproximació per a la descripció de la deformació estructural. Així, aquesta simulació per ordinador suposa una important eina per entendre la funcionalitat de ceràmiques arqueològiques. Aquest procediment representa un model quantitatiu per predir el trencament de l’objecte ceràmic quan aquest és sotmès a diferents condicions de pressió. Aquest model ha estat aplicat a diferents tipologies amforals. Els resultats preliminars mostren diferències significatives entre la tipologia pre-romana i les tipologies romanes, així com entre els mateixos dissenys amforals romans, d’importants implicacions arqueològiques.

On two examples by Iyama and Yoshino

In a recent paper Iyama and Yoshino consider two interesting examples of isolated singularities over which it is possible to classify the indecomposable maximal Cohen-Macaulay modules in terms of linear algebra data. In this paper we present two new approaches to these examples. In the first approach we give a relation with cluster categories. In the second approach we use Orlov's result on the graded singularity category. We obtain some new results on the singularity category of isolated singularities which may be interesting in their own right.

An improved silver staining procedure for schizodeme analysis in polyacrylamide gradient gels

A simple protocol is described for the silver staining of polyacrylamide gradient gels used for the separation of restriction fragments of kinetoplast DNA [schizodeme analysis of trypanosomatids (Morel et al., 1980)]. The method overcomes the problems of non-uniform staining and strong background color which are frequently encountered when conventional protocols for silver staining of linear gels. The method described has proven to be of general applicability for DNA, RNA and protein separations in gradient gels.

The Commons and anti-commons problems in the tourism economy

Countries specialised in tourism tend to face two problems with contradictory effects: the commons and the anti-commons, which lead to tourism over- and under-production, respectively. This paper develops a two-period model to analyse the joint effects of both problems on a small and remote tourism economy. Congestion and the complementariness between foreign transport and local tourism services are key features in this type of markets. As a result, direct selling and the presence of foreign tour-operators emerge as possible market arrangements with different implications in terms of welfare and public intervention. Four main results are obtained. First, in the direct selling situation the optimal policy depends on the relative importance of the problems. Second, the existence of tour-operators always leads to tourism over-production. Third, the presence of a single tour-operator does not solve the congestion problem. Lastly, the switch from several tour-operators to a single one is welfare reducing.

La programació al servei de la matemàtica

Treball de recerca realitzat per un alumne d'ensenyament secundari i guardonat amb un Premi CIRIT per fomentar l'esperit cientí­fic del Jovent l'any 2009. La programació al servei de la matemàtica és un programa informàtic fet amb Excel i Visual Basic. Resol equacions de primer grau, equacions de segon grau, sistemes d'equacions lineals de dues equacions i dues incògnites, sistemes d'equacions lineals compatibles determinats de tres equacions i tres incògnites i troba zeros de funcions amb el teorema de Bolzano. En cadascun dels casos, representa les solucions gràficament. Per a això, en el treball s'ha hagut de treballar, en matemàtiques, amb equacions, nombres complexos, la regla de Cramer per a la resolució de sistemes, i buscar la manera de programar un mètode iteratiu pel teorema de Bolzano. En la part gràfica, s'ha resolt com fer taules de valors amb dues i tres variables i treballar amb rectes i plans. Per la part informàtica, s'ha emprat un llenguatge nou per l'alumne i, sobretot, ha calgut saber decidir on posar una determinada instrucció, ja que el fet de variar-ne la posició una sola lí­nea ho pot canviar tot. A més d'això, s'han resolt altres problemes de programació i també s'ha realitzat el disseny de pantalles.

Intestinal protein absorption in malnourished mice with acute schistosomiasis mansoni

Intestinal protein absorption was studied in undernourished albino Swiss mice with acute schistosomiasis mansoni. Undernutrition was induced by feeding mice with the Regional Basic Diet (RBD) ingested by human populations in Northeast Brazil, an experimental model previously developed in our laboratory. Weaning mice were infected with 40 cercariae and compared to undernourished non-infected mice and/or to infected mice fed a balanced control diet. Apparent and True Protein Absorption Coefficients were determined by nitrogen balance during five consecutive days ending at the 63rd day of the trial (acute phase of murine schistosomiasis). Fecal metabolic nitrogen (FMN) was determined after administration of a non-protein diet and was also calculated through linear regression. Our results showed a reduced protein absorption in non-infected RBD-fed mice as compared to mice fed a casein control diet. Infection with Schistosoma mansoni had apparently no effect on intestinal protein absorption in well-nourished mice. However, infection seemed to interfere with protein absorption in under-nourished animals, since the lowest absorption ratios have been detected among RBD-fed infected mice. A brief discussion is made on the advantages of using the method of linear regression for the determination of FMN.

New insights on river water chemistry by using non-centred simplicial principal component analysis: a case study

The use of perturbation and power transformation operations permits the investigation of linear processes in the simplex as in a vectorial space. When the investigated geochemical processes can be constrained by the use of well-known starting point, the eigenvectors of the covariance matrix of a non-centred principalcomponent analysis allow to model compositional changes compared with a reference point.The results obtained for the chemistry of water collected in River Arno (central-northern Italy) have open new perspectives for considering relative changes of the analysed variables and to hypothesise the relative effect of different acting physical-chemical processes, thus posing the basis for a quantitative modelling

Controladores PI con acción de reset

El control automàtic exerceix un paper important en molts processos de la industria. Cada un dels sistemes de control requereix d’un controlador, la majoria dels quals són del tipus PI. L’objectiu d’aquest projecte es investigar tècniques que permetin superar les limitacions que tenen els controladors PI lineals. En la resposta d’un sistema de control es poden distingir dues tasques diferents: El seguiment a un canvi d’entrada o consigna correspon a la tasca de servo, mentre que el rebuig a pertorbacions correspon a la tasca de regulatori. Al típic esquema de control realimentat, aquestes dues tasques estan enfrontades, és a dir, una millora a la tasca de servo implica un empitjorament a la tasca de regulatori i a l’inversa. Això suposa un problema al rendiment del sistema, així com la necessitat d’establir un cert compromís entre les dues tasques. El que es pretén en aquest projecte es implementar senzilles regles de control no lineal amb la finalitat de millorar el rendiment del sistema i evitar la necessitat d’establir un compromís entre les dues tasques. Així, es pretén superar les limitacions que aquest té, obtenint controladors PI alternatius fàcilment sintetitzables.

A mixed H2/H∞-based semiactive control for vibration mitigation in flexible structures

In this paper, we address this problem through the design of a semiactive controller based on the mixed H2/H∞ control theory. The vibrations caused by the seismic motions are mitigated by a semiactive damper installed in the bottom of the structure. It is meant by semiactive damper, a device that absorbs but cannot inject energy into the system. Sufficient conditions for the design of a desired control are given in terms of linear matrix inequalities (LMIs). A controller that guarantees asymptotic stability and a mixed H2/H∞ performance is then developed. An algorithm is proposed to handle the semiactive nature of the actuator. The performance of the controller is experimentally evaluated in a real-time hybrid testing facility that consists of a physical specimen (a small-scale magnetorheological damper) and a numerical model (a large-scale three-story building)