Null Condition for Semilinear Wave Equation with Variable Coefficients

∗The author was partially supported by M.U.R.S.T. Progr. Nazionale “Problemi Non Lineari...”In this work we analyse the nonlinear Cauchy problem (∂tt − ∆)u(t, x) = ( λg + O(1/(1 + t + |x|)^a) ) ) ∇t,x u(t, x), ∇t,x u(t, x) ), whit initial data u(0, x) = e u0 (x), ut (0, x) = e u1 (x). We assume a ≥ 1, x ∈ R^n (n ≥ 3) and g the matrix related to the Minkowski space. It can be considerated a pertubation of the case when the quadratic term has constant coefficient λg (see Klainerman [6]) We prove a global existence and uniqueness theorem for very regular initial data. The proof avoids a direct application of Klainermann method (Null condition, energy conformal method), because the result is obtained by a combination beetwen the energy estimate (norm L^2 ) and the decay estimate (norm L^∞ )

On a Centrality Maximization Game

The Bonacich centrality is a well-known measure of the relative importance of nodes in a network. This notion is, for example, at the core of Google's PageRank algorithm. In this paper we study a network formation game where each player corresponds to a node in the network to be formed and can decide how to rewire his m out-links aiming at maximizing his own Bonacich centrality, which is his utility function. We study the Nash equilibria (NE) and the best response dynamics of this game and we provide a complete classification of the set of NE when m=1 and a fairly complete classification of the NE when m=2. Our analysis shows that the centrality maximization performed by each node tends to create undirected and disconnected or loosely connected networks, namely 2-cliques for m=1 and rings or a special "Butterfly"-shaped graph when m=2. Our results build on locality property of the best response function in such game that we formalize and prove in the paper.Comment: 10 pages, 11 figure

¿CÓMO MEDIR LOS RESULTADOS DE LA GESTIÓN? UNA EXPERIENCIA UNIVERSITARIA

Con el fin de lograr los objetivos estratégicos determinados a partir de su misión y su visión, las universidades requieren de herramientas efectivas que permitan mejorar los sistemas de gestión y control. El sistema de control es un medio para expandir la estrategia en toda la organización. Desarrolla actividades de planificación, control y diagnóstico y, a partir de la medición y análisis de los resultados, permite evaluar el desempeño de la institución desde múltiples ángulos o criterios. De esta manera, facilita la toma de decisiones en función de los recursos disponibles, con una orientación hacia su mejora permanente. Es una herramienta para gestionar el cambio. Es necesario poder garantizar que las actividades reales de la universidad coincidan con las actividades planificadas. Y esta necesidad es mayor en la medida en que las instituciones se enfrentan a un entorno dinámico y cambiante, a un mayor nivel de incertidumbre y a una alta rivalidad competitiva. Ante esta necesidad, la Universidad Maza ha desarrollado un software que posibilita la implementación de la herramienta de gestión estratégica llamada ‘Tablero de Comando’. El objetivo del desarrollo es la implementación de un Sistema Integrado de Seguimiento del Plan de Gestión 2013 – 2016 de la institución, como base de control tanto de procesos administrativos como académicos. Este instrumento integra el plan estratégico con los procesos decisionales y con el análisis del rendimiento. Es decir, permite monitorear el cumplimiento del plan estratégico efectuando el seguimiento de la ejecución de los objetivos claves a través de la medición de indicadores. El software se fundamenta en los principios determinados por Norton y Kaplan (2000), quienes sentaron las bases teóricas sobre las cuales se desarrolla esta aplicación afirmando que el Cuadro de Mando Integral traduce la estrategia y la misión de una organización en un amplio conjunto de medidas de actuación, que proporcionan la estructura necesaria para un sistema de gestión y medición estratégica (Norton y Kaplan, 2000). El concepto novedoso del Tablero de Comando, es que se basa en tres dimensiones de tiempo, ayer, hoy y mañana, y logra unir el control operativo a corto plazo con la visión y la estrategia a largo plazo

Pianificazione strategica del turnaround: analisi e valutazione dell'azienda "Sigma s.r.l."

Obiettivo di questa tesi è quello di fornire delle linee guida affinché un azienda possa affrontare il processo di rinnovamento in maniera coerente e sostenibile. La trattazione inizia individuando “chi è” il soggetto economico e “chi” governa l’azienda, successivamente si descrive il ruolo che le strategie di risanamento svolgono nei processi di cambiamento strategico e organizzativo ed infine si analizza il caso dell’azienda “Sigma”. Nel case study si descrivono le principali caratteristiche dell’azienda, la sua storia e le sue tradizioni, la formula imprenditoriale perseguita, le caratteristiche del sistema organizzativo, competitivo e sociale in cui l’azienda opera, non trascurando la dimensione finanziario – patrimoniale ed economico – reddituale. Dopo aver effettuato una valutazione dell’azienda e avendo identificato le determinanti del valore aziendale, si cercherà di capire come si possa agire su di esse, nello specifico si identificheranno le potenzialità inespresse, eventualmente presenti. Infine, avendo svolto questi processi di analisi, si arriverà alla sintesi, cioè si capirà se è necessario dar luogo ad un processo di turnaround oppure avviare una fase di liquidazione aziendale, ponendo cosi fine alla vita dell’azienda. Nella descrizione del processo di turnaround ci si soffermerà sulle azioni che è necessario porre in essere per attuare una ristrutturazione organizzativa e finanziaria, recuperando i livelli di fiducia fisiologici per lo svolgimento delle attività aziendali

Existence de solutions globales pour des problèmes hyperboliques non-linéaires

On considère le problème de Cauchy pour des équations hyperboliques à données initiales petites. On prouve l'existence d'une solution globale dans trois cas : # équations hyperboliques ayant une partie non-linéaire qui satisfait la condition nulle de Klainerman, # équation du type de Kirchhoff, # équation de Klein-Gordon non-linéaire avec une masse m = m(e) qui tend vers zéro quand e tends vers 0.We consider the Cauchy problem for hyperbolic equations with small initial data. We prove the globale existence of a solution in the following cases : # hyperbolic equations with non-linear terms satisfying the null condition of Klainerman, # a Kirchhoff type équation, # non linear Klein-Gordon equation, where the mass m(e) decreases to zero as e 0

Synchronous tumours detected during cancer patient staging : prevalence and patterns of occurrence in multidetector computed tomography

Purpose: The incidental detection of one or more additional primary tumours during computed tomography (CT) staging of a patient with known malignancy is rare but possible. This occurrence should be considered by the radiologist when a new lesion is detected, especially if the lesion location is atypical for metastases. The purpose of this report was to document the usefulness of total body CT scan to detect synchronous primary malignancies in cancer patients undergoing a staging workup. Material and methods: This was done by reviewing the staging CT studies of the adult patients with a newly diagnosed cancer evaluated during a five-year period in a single cancer institute in order to identify any possible correlation, establishing which tumours are more frequently combined with a second tumour and which second tumours are more commonly present. Results: Among the patients with a second tumour, the most frequent first primary tumours were melanoma (eight patients, 17.8%), lymphoma (seven patients, 15.6%), and prostate carcinoma (seven patients, 15.6%). The most frequent incidentally detected second tumours were hepatocellular carcinoma (nine patients, 20% of 45 incidental tumours), renal carcinoma (eight patients, 17.8%), lung carcinoma (seven patients, 15.6%), and bladder carcinoma (four patients, 8.9%). One patient had three primary tumours synchronously. Conclusions: We believe that the radiologist's knowledge of the prevalence and pattern of occurrence of these multiple primary malignancies represents added diagnostic value

A demand-based methodology for planning the bus network of a small or medium town

This work aims at developing a demand-based methodology for designing the bus network of a small or medium town. The proposed modelling tool adopts a multi-agent objective function which evaluates performance in the context of different stakeholders: the surplus of travellers (car and bus users); the bus service provider’s revenues and operation costs. This approach was applied to an existing bus network, serving Trapani, which is a medium town in the south of Italy (Sicily), with 100000 inhabitants. The busbased public transport system attracts only about 5% of commuter trips within Trapani (source: National Institute of Statistics, 2005). This paper reports on an analysis of the application of the proposed multiagent modelling tool to two planning scenarios: the first is short-term and characterized by a budget constraint (slight changes in the availability of drivers and vehicles) and the second long-term with new investments in new buses to improve services and increase patronage. In both cases, the impact of the recent car park charging policy launched by the local administration was considered. The decision variables for the optimisation procedure were route, service frequency and capacity of each bus line. A random utility model was employed to forecast the mode choices for trips within Trapani and the travel demand-supply equilibrium was obtained using the DUE (deterministic user equilibrium) assignment algorithm, for private transport, and the hyperpath network loading algorithm, for public transport. The optimisation procedure led to a more efficient bus network characterized by increase in bus frequencies and a better performance in terms of reduced travel time, especially for trips bound for the “old town” in the morning. In addition, a higher number of origin-destination pairs were served, at the expense of the need to interchange between the inner more frequent and the outer less frequent services. This implied that the number of transfers from one bus line to another significantly increased

On a Network Centrality Maximization Game

We study a network formation game where $n$ players, identified with the nodes of a directed graph to be formed, choose where to wire their outgoing links in order to maximize their PageRank centrality. Specifically, the action of every player $i$ consists in the wiring of a predetermined number $d_i$ of directed out-links, and her utility is her own PageRank centrality in the network resulting from the actions of all players. We show that this is a potential game and that the best response correspondence always exhibits a local structure in that it is never convenient for a node $i$ to link to other nodes that are at incoming distance more than $d_i$ from her. We then study the equilibria of this game determining necessary conditions for a graph to be a (strict, recurrent) Nash equilibrium. Moreover, in the homogeneous case, where players all have the same number $d$ of out-links, we characterize the structure of the potential maximizing equilibria and, in the special cases $d=1$ and $d=2$, we provide a complete classification of the set of (strict, recurrent) Nash equilibria. Our analysis shows in particular that the considered formation mechanism leads to the emergence of undirected and disconnected or loosely connected networks.Comment: 42 pages, 11 figure

Imaging follow-up after liver transplantation

Liver transplantation (LT) represents the best treatment for end-stage chronic liver disease, acute liver failure and early stages of hepatocellular carcinoma. Radiologists should be aware of surgical techniques to distinguish a normal appearance from pathological findings. Imaging modalities, such as ultrasound, CT and MR, provide for rapid and reliable detection of vascular and biliary complications after LT. The role of imaging in the evaluation of rejection and primary graft dysfunction is less defined. This article illustrates the main surgical anastomoses during LT, the normal appearance and complications of the liver parenchyma and vascular and biliary structures.Liver transplantation (LT) represents the best treatment for end-stage chronic liver disease, acute liver failure and early stages of hepatocellular carcinoma. Radiologists should be aware of surgical techniques to distinguish a normal appearance from pathological findings. Imaging modalities, such as ultrasound, CT and MR, provide for rapid and reliable detection of vascular and biliary complications after LT. The role of imaging in the evaluation of rejection and primary graft dysfunction is less defined. This article illustrates the main surgical anastomoses during LT, the normal appearance and complications of the liver parenchyma and vascular and biliary structures

Previsione dell'inquinamento generato dalla mobilità veicolare e traffic management

Questo studio s'inserisce in una più ampia attività di ricerca sulle correlazioni tra le concentrazioni dei principali agenti inquinanti e variabili relative sia alle condizioni meteorologiche, che ne possono favorire o meno la dispersione, sia al deflusso veicolare quale fonte primaria d'inquinamento. L'idea è quella di sviluppare una metodologia per la previsione a breve termine delle densità di quegli elementi per i quali la normativa prevede delle soglie in termini di concentrazioni medie orarie. Tutto ciò al fine di potersi avvalere, in futuro, di modelli e tecnologie per sapere, con qualche ora di anticipo, se in una determinata zona di un centro urbano, un giorno, possa verificarsi qualche superamento dei suddetti vincoli di legge e poter, così, implementare tempestivamente strategie di traffic management a salvaguardia della salute dei cittadini. In particolare, questa memoria illustra i primi risultati della ricerca, che riguardano il confronto tra i modelli statistici per l'analisi delle serie storiche (modelli ARIMAX, Auto-Regressive Integrated Moving Average with eXogenous variables) e le reti neuronali, in relazione all'accuratezza della previsione dei livelli d'inquinamento atmosferico. In questa prima fase, la valutazione comparativa riguarda la previsione delle concentrazioni di biossido di azoto (NO2) rilevate nell'anno 2007 da una centralina di monitoraggio della qualità dell'aria e delle condizioni meteorologiche in un'arteria stradale della città di Londra, Marylebone Road. È in programma l'estensione dell'analisi alla città di Palermo