1,721,047 research outputs found
Implementation of a mathematical model for unsteady flow in irrigation channel networks with application to the case of management of Canale Vacchelli, Consorzio Irrigazioni Cremonesi
Full text linkA scala globale, il 70% dei prelievi di acqua è utilizzato in agricoltura; inoltre, la popolazione che basa il proprio sostentamento sui prodotti dell’agricoltura è in aumento. Tutto ciò in un contesto di conclamato cambiamento climatico. Da queste semplici considerazioni appare evidente come la gestione, il controllo e l’ottimizzazione della distribuzione dei volumi idrici in agricoltura abbia un’importanza fondamentale. In particolare, tale considerazione è rafforzata dal fatto che generalmente i Consorzi Irrigui sono istituzioni antiche che gestiscono la distribuzione delle risorse irrigue attuando soluzioni di «equilibrio» frutto dell’esperienza maturata negli anni, esperienza che potrebbe tuttavia rivelarsi non adatta alle condizioni future imposte dal cambiamento climatico. Uno strumento razionale e fisicamente basato che può essere d’aiuto nell’ottimizzazione del processo di distribuzione è fornito dalle Equazioni di Saint-Venant che, affiancato al ruolo del personale esperto, può rendere la gestione delle reti irrigue più efficiente. Il presente studio tratta dell’implementazione di un modello numerico che permetta di risolvere le equazioni di Saint-Venant nella formulazione monodimensionale per una rete di canali a pelo libero interconnessi tra loro secondo una topologia sufficientemente generale. Poiché un modello che abbia come obiettivo la modellazione di una rete irrigua deve integrare, mediante opportune condizioni al contorno interne, alcuni manufatti idraulici fondamentali, con i quali viene attuata la regolazione delle portate in ingresso alla rete irrigua e delle portate erogate ai canali secondari, tale componente costituisce un aspetto presente nel modello implementato. Inoltre, l’attività sperimentale svolta nell’ambito di questa Tesi ha consentito di constatare l’effetto del processo di crescita delle macrofite sulla scabrezza idraulica dei canali nel corso della stagione irrigua. La crescita e sviluppo della vegetazione è governata principalmente dalla radiazione solare, dalla presenza di nutrienti e dalla temperatura dell’acqua. Per tale ragione si è deciso di accoppiare al modello idraulico implementato, un modello termico che permetta di modellare la temperatura del corso d’acqua in tutto il dominio considerato e per l’intera stagione irrigua. Nella Tesi sono mostrati i passi percorsi per l’implementazione e validazione delle varie componenti descritte e l’applicazione delle stesse al Canale Vacchelli, il più importante canale gestito dal Consorzio Irrigazioni Cremonesi e uno dei più importanti in nord Italia.On a global scale, 70% of water withdrawals are used in agriculture; furthermore, the population that bases its livelihood on agricultural products is increasing. All this in a context of clear climate change. From these simple considerations it is clear that the management, control and optimization of the distribution of water volumes in agriculture has a fundamental importance. In particular, this consideration is strengthened by the fact that generally the Irrigation Consortia are ancient institutions that manage the distribution of irrigation resources by implementing "equilibrium" solutions resulting from the experience gained over the years, experience that could however not suitable for the future conditions imposed by climate change. A rational and physically based tool that can be of help in optimizing the distribution process is provided by the Saint-Venant Equations which, combined with the role of expert personnel, can make the management of irrigation networks more efficient. This study deals with the implementation of a numerical model that allows to solve the Saint-Venant equations in the one-dimensional formulation for a network of free-surface channels interconnected according to a sufficiently general topology. Since a model that has as its objective the modeling of an irrigation network must integrate, through appropriate internal boundary conditions, some fundamental hydraulic works, with which the regulation of the incoming flows to the irrigation network and of the flows delivered to the secondary channels is implemented, this component is present in the implemented model. Furthermore, the experimental activity carried out in the context of this Thesis has allowed to observe the effect of the growth process of macrophytes on the hydraulic roughness of the channels during the irrigation season. The growth and development of vegetation is mainly governed by solar radiation, the presence of nutrients and the temperature of the water. For this reason, it was decided to couple the implemented hydraulic model with a thermal model that allows modeling the temperature of the canal network for the entire irrigation season. This Thesis shows the steps taken for the implementation and validation of the various components described and their application to the Canale Vacchelli, the most important canal managed by the Consorzio Irrigazioni Cremonesi and one of the most important in northern Italy
Extensive-form perfect equilibrium computation in two-player games
No full textWe study the problem of computing an Extensive-Form Perfect Equilibrium (EFPE) in 2-player games. This equilibrium concept refines the Nash equilibrium requiring resilience with respect to a specific vanishing perturbation, representing mistakes of the players at each decision node. The scientific challenge is intrinsic to the EFPE definition: it requires a perturbation over the agent form, but the agent form is computationally inefficient due to the presence of highly nonlinear constraints. We show that the sequence form can be exploited in a non-trivial way and that, for general-sum games, finding an EFPE is equivalent to solving a suitably perturbed linear complementarity problem. We prove that Lemke's algorithm can be applied, showing that computing an EFPE is PPAD-complete. In the notable case of zero-sum games, the problem is in FP and can be solved by linear programming. Our algorithms also allow one to find a Nash equilibrium when players cannot perfectly control their moves, being subject to a given execution uncertainty, as is the case in most realistic physical settings
Adopting the Cascade Model in Ad Auctions: Efficiency Bounds and Truthful Algorithmic Mechanisms
Full text linkAd Auctions and Cascade Model: GSP Inefficiency and Algorithms
Full text linkThe design of the best economic mechanism for Sponsored Search Auctions (SSAs) is a central task in computational mechanism design/game theory. Two open questions concern (i) the adoption of user models more accurate than the currently used one and (ii) the choice between Generalized Second Price auction (GSP) and Vickrey–Clark–Groves mechanism (VCG). In this paper, we provide some contributions to answer these questions. We study Price of Anarchy (PoA) and Price of Stability (PoS) over social welfare and auctioneer’s revenue of GSP w.r.t. the VCG when the users follow the famous cascade model. Furthermore, we provide exact, randomized, and approximate algorithms, showing that in real–world settings (Yahoo! Webscope A3 dataset, 10 available slots) optimal allocations can be found in less than 1s with up to 1,000 ads, and can be approximated in less than 20ms even with more than 1,000 ads with an average accuracy greater than 99%
Effects of Anthropic Changes on the Propagation of the Gleno Dam Break Wave in the Valle Camonica Floodplain
Full text linkViolence Against Healthcare: A Public Health Issue beyond Conflict Settings
No full textA 3-year analysis released in August 2021 by the WHO indicated that more than 700 healthcare workers and patients have died (2,000 injured) as a result of attacks against health facilities since 2017. The COVID-19 pandemic has made the risks even worse for doctors, nurses, and support staff, unfortunately. According to the latest figures from the International Committee of the Red Cross, 848 COVID-19-related violent incidents were recorded in 2020, and this is likely an underrepresentation of a much more widespread phenomenon. In response to rises in COVID-19-related attacks against healthcare, some countries have taken action. In Algeria, for instance, the penal code was amended to increase protection for healthcare workers against attacks and to punish individuals who damage health facilities. In the United Kingdom, the police, crime, sentencing, and courts bill proposed increased the maximum penalty from 12 months to 2 years in prison for anyone who assaults an emergency worker. Measures taken by countries represent a good practical way to counteract this crisis within COVID-19. However, we stress the importance of primary prevention with the use of communication: social media and other communication channels are fundamentally important to combat violence against health professionals, both to inform the population with quality data and to disseminate campaigns to prevent these acts
Optimal correlated equilibria in general-sum extensive-form games: fixed-parameter algorithms, hardness, and two-sided column-generation
No full textFaster no-regret learning dynamics for extensive-form correlated and coarse correlated equilibria
No full text
- …
