UdG i Bolonya: millorar per aprendre més

Informació esquemàtica sobre els punts més importants del procés de Bolonya i l'adaptació a l'Espai Europeu d'Ensenyament Superior i també els següents escrits: Guia per a l’adaptació de la Universitat de Girona a l’espai europeu d’educació superior i Docència a la UdG: docència 2010

Què vull saber sobre la nota de tall... i no m'atreveixo a preguntar

Un bon batxillerat o uns bons cicles formatius són cosa de tots. Resulta imprescindible que l'orientació es faci i aquesta elecció és feina teva. També és necessari, però, que hi participin els professors i, sobretot, ha de tenir la complicitat de la familia, perquè és una decisió que tindrà repercussions importants i cal mesurar molt bé el camí que es tria

Javier Cercas, el professor i el novel·lista

Perfil biogràfic de Javier Cercas

Els estudiants han de mirar a la societat i ser valents

Jesús Garcia Gil dirigeix Microbial, una iniciativa empresarial de referència especialitzada en sistemses de detecció ràpida de bacteris. Aquest microbiòleg és catedràtic de la UdG i els darrers cinc anys ha dirigit del Departament de Biologia. Microbial és una spin-off nascuda a la Universitat de Girona i ha estat la primera empresa de la xarxa UniBa que ha tancat un acord amb inversors privats

Problemes de física per a batxillerat i cicles formatius [versió html]

Aquest manual recull un conjunt de problemes que engloben els principals camps de la física clàsica. El seu enfocament està dirigit a estudis preuniversitaris (batxillerat, cicles formatius de grau superior) i pretén ser un complement tant dels manuals ja existents, com una ajuda per aquells estudiants ja universitaris que vulguin repassar els seus coneixements previs

Tendències en el disseny de productes: passat, present i futur [versió html]

L’àmbit del disseny industrial i disseny de producte abasta una gran quantitat de coneixement i especialitats, no existint fins al moment cap escrit respecte a tendencies en el disseny, que s’adapti als ensenyaments impartits a l’escola. Amb ànim de donar resposta a aquesta necessitat s’edita aquest volum, que ha de ser d’ús pels estudiants de les diverses enginyeries i de disseny. També pot ser d’ajut a aquells alumnes que en el seu Projecte Final de Carrera tractin temes relacionats amb el disseny i desenvolupament de productes

Sistemes integrats de gestió: qualitat, medi ambient i prevenció: presentacions [versió html]

Les organitzacions es veuen actualment envoltades d’un entorn en constant canvi. Les empreses que volen sobreviure en aquest context de creixent competitivitat i internacionalització dels mercats, tenen en els models de gestió una eina per a la millora de la seva gestió diària, la presa de decisions en l’empresa i l’establiment d’una estratègia que les ajudi a avançar cap a l’excel·lència empresarial. Els models de gestió empresarial neixen amb la idea de fomentar aquest paradigma de la qualitat i han anat evolucionant fins a arribar als anomenats Sistemes Integrats de Gestió, SIG, que aborden la gestió de la qualitat, el medi ambient i la seguretat d’una manera conjunta

Instrumentació i anàlisi de dades d'assaigs de bigues de formigó armades amb barres de FRP

Estudi experimental del comportament de bigues de formigó armades amb barres de materials compostos de matriu polimèrica (FRP)

Pla de creació de l'empresa de producció i comercialització de carn d'oví "Xai Pigallat" situada al terme municipal de Riudaura (La Garrotxa)

Estudi dels paràmetres més rellevants en la creació d'una empresa agropecuària (identificació del projecte, equip fundador, anàlisi del mercat, pla de marqueting, pla d'organització, pla jurídic - fiscal i pla econòmic- financer per tal de valorar la viabilitat de l'empresa "Xai pigallat" de Ridaura (La Garrotxa)

The single principle of compositional data analysis, continuing fallacies, confusions and misunderstandings and some suggested remedies

In any discipline, where uncertainty and variability are present, it is important to have principles which are accepted as inviolate and which should therefore drive statistical modelling, statistical analysis of data and any inferences from such an analysis. Despite the fact that two such principles have existed over the last two decades and from these a sensible, meaningful methodology has been developed for the statistical analysis of compositional data, the application of inappropriate and/or meaningless methods persists in many areas of application. This paper identifies at least ten common fallacies and confusions in compositional data analysis with illustrative examples and provides readers with necessary, and hopefully sufficient, arguments to persuade the culprits why and how they should amend their ways

Inference of distributional parameters from compositional samples containing nondetects

Low concentrations of elements in geochemical analyses have the peculiarity of being compositional data and, for a given level of significance, are likely to be beyond the capabilities of laboratories to distinguish between minute concentrations and complete absence, thus preventing laboratories from reporting extremely low concentrations of the analyte. Instead, what is reported is the detection limit, which is the minimum concentration that conclusively differentiates between presence and absence of the element. A spatially distributed exhaustive sample is employed in this study to generate unbiased sub-samples, which are further censored to observe the effect that different detection limits and sample sizes have on the inference of population distributions starting from geochemical analyses having specimens below detection limit (nondetects). The isometric logratio transformation is used to convert the compositional data in the simplex to samples in real space, thus allowing the practitioner to properly borrow from the large source of statistical techniques valid only in real space. The bootstrap method is used to numerically investigate the reliability of inferring several distributional parameters employing different forms of imputation for the censored data. The case study illustrates that, in general, best results are obtained when imputations are made using the distribution best fitting the readings above detection limit and exposes the problems of other more widely used practices. When the sample is spatially correlated, it is necessary to combine the bootstrap with stochastic simulation

When zero doesn't mean it and other geomathematical mischief

There is almost not a case in exploration geology, where the studied data doesn’t includes below detection limits and/or zero values, and since most of the geological data responds to lognormal distributions, these “zero data” represent a mathematical challenge for the interpretation. We need to start by recognizing that there are zero values in geology. For example the amount of quartz in a foyaite (nepheline syenite) is zero, since quartz cannot co-exists with nepheline. Another common essential zero is a North azimuth, however we can always change that zero for the value of 360°. These are known as “Essential zeros”, but what can we do with “Rounded zeros” that are the result of below the detection limit of the equipment? Amalgamation, e.g. adding Na2O and K2O, as total alkalis is a solution, but sometimes we need to differentiate between a sodic and a potassic alteration. Pre-classification into groups requires a good knowledge of the distribution of the data and the geochemical characteristics of the groups which is not always available. Considering the zero values equal to the limit of detection of the used equipment will generate spurious distributions, especially in ternary diagrams. Same situation will occur if we replace the zero values by a small amount using non-parametric or parametric techniques (imputation). The method that we are proposing takes into consideration the well known relationships between some elements. For example, in copper porphyry deposits, there is always a good direct correlation between the copper values and the molybdenum ones, but while copper will always be above the limit of detection, many of the molybdenum values will be “rounded zeros”. So, we will take the lower quartile of the real molybdenum values and establish a regression equation with copper, and then we will estimate the “rounded” zero values of molybdenum by their corresponding copper values. The method could be applied to any type of data, provided we establish first their correlation dependency. One of the main advantages of this method is that we do not obtain a fixed value for the “rounded zeros”, but one that depends on the value of the other variable. Key words: compositional data analysis, treatment of zeros, essential zeros, rounded zeros, correlation dependency

Discrete and continuous compositions

This paper examines a dataset which is modeled well by the Poisson-Log Normal process and by this process mixed with Log Normal data, which are both turned into compositions. This generates compositional data that has zeros without any need for conditional models or assuming that there is missing or censored data that needs adjustment. It also enables us to model dependence on covariates and within the composition

Bayesian tools for zero counts in compositional data

The log-ratio methodology makes available powerful tools for analyzing compositional data. Nevertheless, the use of this methodology is only possible for those data sets without null values. Consequently, in those data sets where the zeros are present, a previous treatment becomes necessary. Last advances in the treatment of compositional zeros have been centered especially in the zeros of structural nature and in the rounded zeros. These tools do not contemplate the particular case of count compositional data sets with null values. In this work we deal with \count zeros" and we introduce a treatment based on a mixed Bayesian-multiplicative estimation. We use the Dirichlet probability distribution as a prior and we estimate the posterior probabilities. Then we apply a multiplicative modi¯cation for the non-zero values. We present a case study where this new methodology is applied. Key words: count data, multiplicative replacement, composition, log-ratio analysis

CODAPACK3D. A new version of Compositional Data Package

The statistical analysis of compositional data should be treated using logratios of parts, which are difficult to use correctly in standard statistical packages. For this reason a freeware package, named CoDaPack was created. This software implements most of the basic statistical methods suitable for compositional data. In this paper we describe the new version of the package that now is called CoDaPack3D. It is developed in Visual Basic for applications (associated with Excel©), Visual Basic and Open GL, and it is oriented towards users with a minimum knowledge of computers with the aim at being simple and easy to use. This new version includes new graphical output in 2D and 3D. These outputs could be zoomed and, in 3D, rotated. Also a customization menu is included and outputs could be saved in jpeg format. Also this new version includes an interactive help and all dialog windows have been improved in order to facilitate its use. To use CoDaPack one has to access Excel© and introduce the data in a standard spreadsheet. These should be organized as a matrix where Excel© rows correspond to the observations and columns to the parts. The user executes macros that return numerical or graphical results. There are two kinds of numerical results: new variables and descriptive statistics, and both appear on the same sheet. Graphical output appears in independent windows. In the present version there are 8 menus, with a total of 38 submenus which, after some dialogue, directly call the corresponding macro. The dialogues ask the user to input variables and further parameters needed, as well as where to put these results. The web site http://ima.udg.es/CoDaPack contains this freeware package and only Microsoft Excel© under Microsoft Windows© is required to run the software. Kew words: Compositional data Analysis, Software