177,956 research outputs found
Are R&D subsidies provided optimally? Evidence from a simulated agency-firm stochastic dynamic game
No full textBy means of a simulated funding-agency/supported-firm stochastic dynamic game, this paper firstly shows that not only the level of R&D performed by firms is underprovided (as maintained by traditional literature on the subject), but also the level of the subsidy provided by the funding (public) agency (used to correct exactly for the corporate R&D shortage). This event is due to externalities generated by the agency-firm strategic relationship. Two versions of the model are simulated and compared: one assuming rival behaviors between companies and agency, and one associated to the Social-planner (or cooperative) strategy. Secondly, the paper looks at what “welfare” implications are associated to different degree of funding effect’s persistency. Three main conclusions are drawn: (i) the relative quota of subsidy to R&D is undersized in the rival compared to the Social-planner model; (2) the rivalry strategy generates distortions that favor the agency compared to firms; (3) when passing from less persistent to more persistent R&D additionality/crowding-out effect, the lower the bias the greater the variance is and vice versa. As for the management of R&D funding policies, all the elements favouring greater collaboration between agency and firm objectives can help current R&D support to reach its social optimum.R&D subsidies, Rivalry vs. cooperation, Dynamic-stochastic games, Simulations
Iscrizioni e documenti arabi per la storia della Somalia
No full textPoche sono le testimonianze delle correnti migratorie tra le coste meridionali arabe e quelle somale risalenti a epoche remote: in quest'articolo Cerulli raccoglie una serie di iscrizioni e documenti che gettano luce sullo sviluppo storico di Mogadiscio anteriormente al XVIII secolo.Waa dhif waxyaaba xilli aad u fog la qoray oo muujinaya geeddiga xeebaha koofur Areebiya iyo kuwa soomaaliyeed. Haddaba qoraagani wuxuu qoraalkaan ku soo ururiyay qoraallo ku xardhan derbi iyo qoraallo badan oo muujinayaa koboca taarikheed ee magaalada Muqdisho, xilliigii ka horreeyay qarnigii 18aad.Few are the testimonies of migratory flows between the southern Arabic coasts and Somalia dating back to ancient times: in this article, Cerulli collects a series of inscriptions and documents that shed light on the historical development of Mogadishu before the eighteenth century.Documento messo a disposizione dall'Università di Napoli L'Orientale.Dokumentigan waxaa dadka u soo bandhigay jaamacadda "Università di Napoli L'Orientale".Document provided by the University of Naples L'Orientale
Sperimentazione e confronto di algoritmi per il problema del centro assoluto di una rete
No full textFranco Angeli Editor
Sperimentazione e confronto di algoritmi per il problema del centro assoluto di una rete
No full textFranco Angeli Editor
Relations, models and a memetic approach for three degree-dependent spanning tree problems
No full textAbstract In this paper we take into account three different spanning tree problems with degree-dependent objective functions. The main application of these problems is in the field of optical network design. In particular, we propose the classical Minimum Leaves Spanning Tree problem as a relevant problem in this field and show its relations with the Minimum Branch Vertices and the Minimum Degree Sum Problems. We present a unified memetic algorithm for the three problems and show its effectiveness on a wide range of test instances
Operations management in distribution networks within a smart city framework
No full textThis article studies a vehicle routing problem with environmental constraints that are motivated by the requirements for sustainable urban transport. The empirical research presents a fleet planning problem that takes into consideration both minimum cost vehicle routes and minimum pollution. The problem is formulated as a mixed integer linear programming model and experimentally validated using data collected from a real situation: a grocery company delivering goods ordered via e-channels to customers spread in the urban and metropolitan area of Genoa smart city. The proposed model is a variant of the vehicle routing problem tailored to include environmental issues and street limitations. Its novelty regards also the use of real data instances provided by the B2C grocery company. Managerial implications are the choice of both the routes and the number and type of vehicles. Results show that commercial distribution strategies achieve better results in term of both business and environmental performance, provided the smart mobility goals and constraints are included into the distribution model from the beginning
Finding Pattern Configurations for Bank Cheque Printing
No full textAbstract The problem we address in this paper arises in large-scale manufacturing of bank cheques. Due to security reasons, the cheques must be printed on special (expensive) paper. The first step in the printing process is to prepare the plates that will be used by the composing machine. If the imprint (image) of a particular cheque is on a plate, each time the composing machine uses this plate a new cheque of this type is produced. Each plate has a predefined number of positions to be impressed. Due to delivery due dates, there is an additional constraint requiring each cheque not to be present in more than a predefined number of different plates. There are two different production costs that have to be considered: overproduction costs and printing costs. Each overproduced cheque can be either destroyed or stored in a proper location under surveillance. Both these alternatives have a huge environmental impact, indeed, on the one hand, paper waste is produced, while, on the other hand there is a huge energy consumption. The problem consists in defining the pattern (i.e. the configuration of cheque images) of each plate to be used and the corresponding frequency, such that total costs are minimized. We study this real world problem that is strictly related to the cutting stock problem with pattern minimization. Such a problem is addressed actually by a large cheque manufacturer in Southern part of Italy. We define a very efficient heuristic to solve it. The proposed solution methodology is currently used by the above mentioned manufacturer to define the cheque allocation of the plates
A two-level metaheuristic for the all colors shortest path problem
No full textGiven an undirected weighted graph, in which each vertex is assigned to a color and one of them is identified as source, in the all-colors shortest path problem we look for a minimum cost shortest path that starts from the source and spans all different colors. The problem is known to be NP-Hard and hard to approximate. In this work we propose a variant of the problem in which the source is unspecified and show the two problems to be computationally equivalent. Furthermore, we propose a mathematical formulation, a compact representation for feasible solutions and a VNS metaheuristic that is based on it. Computational results show the effectiveness of the proposed approach for the two problems
A tabu search heuristic based on k-diamonds for the weighted feedback vertex set problem
No full textGiven an undirected and vertex weighted graph G = (V,E,w), the Weighted Feedback Vertex Problem (WFVP) consists of finding a subset F ⊆ V of vertices of minimum weight such that each cycle in G contains at least one vertex in F. The WFVP on general graphs is known to be NP-hard and to be polynomially solvable on some special classes of graphs (e.g., interval graphs, co-comparability graphs, diamond graphs). In this paper we introduce an extension of diamond graphs, namely the k-diamond graphs, and give a dynamic programming algorithm to solve WFVP in linear time on this class of graphs. Other than solving an open question, this algorithm allows an efficient exploration of a neighborhood structure that can be defined by using such a class of graphs. We used this neighborhood structure inside our Iterated Tabu Search heuristic. Our extensive experimental show the effectiveness of this heuristic in improving the solution provided by a 2-approximate algorithm for the WFVPon general graphs
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