1435 research outputs found
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Robust Portfolio Asset Allocation: models and algorithmic approaches
No full textMany financial optimization problems involve future values of security prices, interest rates and exchange rates which are not known in advance, but can only be forecasted or estimated. Such problems fit perfectly into the framework of Robust Optimization that, given optimization problems with uncertain parameters, looks for solutions that will achieve good objective function values for the realization of these parameters in given uncertainty sets.In finance, Robust Optimization offers vehicles to incorporate the estimation of uncertain parameters into the decision making process.This is true, for example, in portfolio asset allocation. Starting from the robust counterparts of the classical mean-variance portfolio problems, in this paper we review some mathematical models that have been recently proposed in the literature to address uncertainty in portfolio asset allocation problems. For some of these, we focus also on algorithmic approaches and computataional issues. Finally, we analyze the relationship between robustness and risk measures
Soluzione di ricorrenze nell'analisi di algoritmi
No full textSi presentano alcuni semplici teoremi per risolvere le relazioni di ricorrenza lineari, bilanciate e di ordine costante, che rappresentano il tempo di funzionamento dei piu' comuni algoritmi ricorsivi
XML Data Mining
No full textXML is the standard language for representing semi-structured data. With the spreading of XML sources, mining XML data can be an important objective in the near future. This paper presents a project focussed on designing a general-purpose query language in support of mining XML data. In our framework, raw data, mining models and domain knowledge are represented by way of XML documents and stored inside XML native databases. Data mining tasks are expressed in an extension of XQuery. Special attention is given to the frequent pattern discovery problem, and a way of exploiting domain-dependent optimizations and efficient data structures as deeper as possible in the extraction process is presented. We report the results of a first bunch of experiments, showing that a good trade-off between expressiveness and efficiency in XML data mining is not a chimera
Handling multiple non functional concerns in behavioural skeletons
No full textWe introduce and address the problem of concurrent autonomic management of different non-functional concerns in parallel applications build as a hierarchical composition of behavioural skeletons.
We first define the problems arising when multiple concerns are dealt with by independent managers, then we propose a methodology supporting coordinated management, and finally we discuss how autonomic management of multiple concerns may be implemented in a typical use case.
The paper concludes with an outline of the challenges involved in realizing the proposed methodology on distributed target architectures such as clusters and grids.
Being based on the behavioural skeleton concept proposed in the CoreGRID GCM, it is anticipated that the methodology will be readily integrated into the current reference implementation of GCM based on Java ProActive and running on top of major grid middlewares
Artificial Intelligence Techniques for Automatic Reformulation of Complex Problems: the I-DARE Project
No full textComplex, hierarchical, multi-scale industrial and natural systems generate increasingly large mathematical models. Practitioners are usually able to formulate such models in their ''natural'' form; however, solving them often requires finding an appropriate reformulation to reveal structures in the model which make it possible to apply efficient, specialized approaches. I-DARE is a structure-aware modeling-reformulation-solving environment based on Declarative Programming. It allows the construction of complex structured models, that can be automatically and algorithmically reformulated to search for the best formulation, intended as the one for which the most efficient solution approach is available. In order to accommodate (potentially) all possible specialized solution methods, it defines a general software framework for solvers, that are ''registered'' to specific problem structures. This article describes in details the application of Artificial Intelligence in the modeling and reformulation modules of I-DARE, showing how Declarative Programming can be used to design a structure-aware modeling environment that allows for a new automatic reformulation methodology
Searching the Best (Formulation, Solver, Configuration) for Structured Problems
No full textComplex, hierarchical, multi-scale industrial and natural systems generate increasingly large mathematical models. I-DARE is a structure-aware modeling-reformulating-solving environment based on Declarative Programming, that allows the construction of complex structured models. The main aim of the system is to produce models that can be automatically and algorithmically reformulated to search for the ''best'' formulation, intended as the one for which the most efficient solution approach is available. This requires exploration of a high-dimensional space comprising all (structured) reformulations of a given instance, all available solvers for (each part of) the formulation, and all possible configurations of the relevant algorithmic parameters for each solver. A fundamental pre-requisite for this exploration is the ability to predict the efficiency of a given (set of) algorithm(s), considering their configuration(s), for a given instance; this is, however, a vastly nontrivial task. This article describes how the I-DARE system organizes the information on the instance at hand in order to make the search in the (formulation, solver, configuration) space possible with several different exploration techniques. In particular, we propose a way to combine general machine learning mechanisms and ad-hoc methods, where available, in order to effectively compute the "objective function" of the search, i.e., the prediction of the effectiveness of a point in the space. We also discuss how this mechanism can take upon itself part of the exploration, the one in the sub-space of configurations, thus simplifying the task to the rest of the system by reducing the dimensionality of the search space it has to traverse
Auctions and barters
No full textIn this technical report we describe a certain number of models of auctions barters and propose the associated procedures. In this way we face the problem of the fair sharing of goods, bads and possibly services (also collectively termed as) among a set of players that cannot or do not want to use a common cardinal scale for the evaluation of the items owing to the very qualitative and non economical nature of the items themselves
Lo spirito del capitalismo
No full textRIASSUNTO Gli autori che rivestono una grande importanza nell’ambito della trattazione sistemica del capitalismo sono: Werner, Sombart, e Max Weber. Alla centralità marxiana del rapporto capitale lavoro si sostituisce la ricerca di schemi di comportamento individuali e collettivi riconducibili al processo storico di razionalizzazione che caratterizza l’occidente. Sombart coniò l’espressione spirito del capitalismo: somma degli atteggiamenti psicologici e culturali che presiedono alla nascita del capitalismo moderno. Il capitalismo del secolo XVI viene proposto in chiave di World economy: sistema economico che progredisce in quanto non viene racchiuso in un sistema politico omogeneo a livello europeo e internazionale. Il decollo del capitalismo avviene in coincidenza con la cosiddetta rivoluzione industriale. Weber è tradizionalmente riconosciuto come uno dei padri della sociologia è unanimemente considerato il Marx della borghesia. Come si evince dalla sua biografia fu una personalità assai complessa; fu tra coloro che si occuparono della stesura della costituzione di Weimar ed in particolar modo alla introduzione del sistema americano di elezione presidenziale. Dopo la sua prima attività di ricerca di storia economica dedicò la sua attività scientifica alla critica della concezione materialistica della storia. E' possibile delineare il percorso di ricerca di Weber attorno ad alcuni ambiti fondamentali e interconnessi:- La questione dell'epistemologia e del metodo delle scienze sociali;- L'analisi della civiltà occidentale moderna;- La definizione dei concetti chiave della sociologia. Weber cerca di chiarire di che cosa la sociologia debba occuparsi; nega la possibilità di analizzare i fenomeni sociali e politici utilizzando le stesse categorie concettuali che le scienze naturali utilizzano per i fenomeni fisici. Le scienze sociali vengono considerate come scienze comprendenti, ovvero scienze che hanno per oggetto l’agire sociale. Lo scienziato sociale è sempre coinvolto in quel che studia quindi le sue deduzioni possono essere condizionate dalla sua esperienza personale, per ovviare a tale inconveniente Weber introduce il concetto di idealtipo. SUMMARY Max Weber (21 April 1864 – 14 June 1920) was one of the most profoundly influential thinkers of the twentieth century. Born in Germany, Weber became a lawyer, politician, scholar, political economist, and sociologist. Weber's major works deal with rationalization in sociology of religion, government, organizational theory, and behavior. His most famous work is his essay The Protestant Ethic and the Spirit of Capitalism, which began his work in the sociology of religion. In this work, Weber argued that religion was one of the non-exclusive reasons for the different ways the cultures of the Occident and the Orient have developed, and stressed that particular characteristics of ascetic Protestantism influenced the development of capitalism, bureaucracy and the rational-legal state in the West. Some have used Weber's work on The Protestant Ethic as an argument that human institutions were not shaped by inevitable materialism, as Marx had argued, but by religious ideals and ideas which could not be reduced to material causation. In another major work, Politics as a Vocation, Weber defined the state as an entity which claims a monopoly on the legitimate use of physical force, a definition that became pivotal to the study of modern Western political science
Synthesis of glycose carbamides and evaluation of the induction of erythroid differentiation of human erythroleukemic K562 cells
No full textSUMMARY A series of carbamides derived from 1,2:5,6-di-O-isopropylidene-D-gluco- (1) and D-allofuranose (3) as well as their 5,6-O-deprotected analogues (2 and 4) and methyl 3,4-O-isopropylidene-alfa- and beta-D-galactopyranosides (5 and 6) have been prepared in order to evaluate their ability to induce erythroid differentiation of human erythroleukemic K562 cells. Twenty out of 51 carbamides tested exhibit an appreciable activity as inducers of erythroid differentiation and have been fully characterized and described
From symmetric subdivision masks of Hurwitz type to interpolatory subdivision masks
No full textSUMMARY In this paper we present a general strategy to deduce a family of interpolatory masks from a symmetric Hurwitz non-interpolatory one. This brings back to a polynomial equation involving the symbol of the non-interpolatory scheme we start with. The solution of the polynomial equation here proposed, tailored for symmetric Hurwitz subdivision symbols, leads to an efficient procedure for the computation of the coefficients of the corresponding family of interpolatory masks. Several examples of interpolatory masks associated with classical approximating masks are given