Solving linear multiplicative programs via branch-and-bound: a computational experience

In this paper, linear multiplicative programs are approached with a branch-and-bound scheme and a detailed computational study is provided. Several underestimation functions are analyzed and various partitioning criteria are presented. A particular class of linear multiplicative programs, useful to solve some applicative bilevel problems, is considered from a theoretical point of view to emphasize an efficient solution method. Detailed results of the computational study are provided to point out the performances provided by using various underestimation functions and partitioning criteria, thus improving some of the results of the current literature

The convergence of the disciplines for stage in high schools

The scientific discoveries gained over the last 70 years now allow us to build a unitary history of the universe that gathers the contributions of many disciplines. These new vision assigns to the Earth Sciences a new and important role to promote the convergence of many disciplines in order to build a unified history of the universe and of man in it. An example of this new role can be found in the Alternanza Scuola-Lavoro ASL (combined experience of study and work). For the Liceo the ASL, is a challenge. It risks becoming another activity that is added to citizenship education, assessment by skills, university orientation. The teachers see this set of activities as an already inadequate subtraction of time. Interesting opportunities are created by engaging students and the whole class council in activities of contextualization of knowledge. Students, with a precise responsibility in a working group, experience some of the typical dynamics of a work situation. From the observation, guided by indicators, and from the evaluation of the products, the teachers can obtain useful indications for inserting the students in the business realities. The Big History Project in Earth\u2019s Science context can be the solution. The students, in groups, study the history of the Universe according, they will have the task of creating a product of their choice. \u201cAvogadro Institute\u201d of Biella has produced videos with Sony Vegas Pro. One has engaged in a History of the Universe in 8 minutes, the other has presented the geological history of Biella. This job could be preparatory to a subsequent ASL in a geopark. In the \u201cA. Banfi\u201d Liceo in Vimercate (MI) it was decided to let the whole class work in the realization of a single product as 30-minute documentary that obtained almost 1500 views on Youtube. An educational trip to the Geological Observatory of Coldigioco has introduced students to the complexity of the geological history of Italy and the international interest it raises. A subsequent inspection in Val d\u2019Ossola, led by the Department of Earth Sciences of the University of Milan, provided the necessary information to relate the remote history of the valley with the recent one. The online attendance of a coding course allowed students to design and implement an application for mobile phones with App Inventor. From the set of evaluative elements such as group work observation tables, the daily report of the progress of the activities on a dedicated platform and the evaluation of the realized products, a profile of the student\u2019s skills can emerge, useful for a subsequent ASL insertion in a company real and also for orientation at the end of high school studies

Access regulation and the transition from copper to fiber networks in telecoms

In this paper we study the impact of different forms of access obligations on firms' incentives to migrate from the legacy copper network to ultra-fast broadband infrastructures. We analyze three different kinds of regulatory interventions: geographical regulation of access to copper networks-where access prices are differentiated depending on whether or not an alternative fiber network has been deployed; access obligations on fiber networks and its interplay with wholesale copper prices; and, finally, a mandatory switch-off of the legacy copper network-to foster the transition to the higher quality fiber networks. Trading-off the different static and dynamic goals, the paper provides guidelines and suggestions for policy makers' decision

Infrastructure Upgrades and Foreclosure with Coexistence of Service-Based and Facility-Based Firms

We investigate the incentives for facility-based firms to invest in infrastructure upgrades and to foreclose service-based firms. We focus on asymmetric regulation regarding servicebased firms' access to the infrastructure held by a facility-based firm. Spillovers from the infrastructure upgrades made by a regulated facility-based firm on service-based firms play a key role in the incentives for making these upgrades. The spillover effect can enhance the incentives for the regulated facility-based firm to make upgrades if access prices are not regulated. The existence of rival facility-based firms strengthens the incentives for a regulated facility-based firm to make infrastructure upgrades, especially when the spillover effect is significant. Furthermore, if access prices are not regulated, the existence of rival facility-based firms weakens the incentives for a regulated facility-based firm to foreclose service-based firms

A global optimization approach to fractional optimal control

In this paper, we consider a fractional optimal control problem governed by system of linear differential equations, where its cost function is expressed as the ratio of convex and concave functions. The problem is a hard nonconvex optimal control problem and application of Pontriyagin's principle does not always guarantee finding a global optimal control. Even this type of problems in a finite dimensional space is known as NP hard. This optimal control problem can, in principle, be solved by Dinkhelbach algorithm [10]. However, it leads to solving a sequence of hard D.C programming problems in its finite dimensional analogy. To overcome this difficulty, we introduce a reachable set for the linear system. In this way, the problem is reduced to a quasiconvex maximization problem in a finite dimensional space. Based on a global optimality condition, we propose an algorithm for solving this fractional optimal control problem and we show that the algorithm generates a sequence of local optimal controls with improved cost values. The proposed algorithm is then applied to several test problems, where the global optimal cost value is obtained for each case