1,721,071 research outputs found
An enhanced lower bound for the Time-Dependent Travelling Salesman Problem
No full textGiven a graph whose arc traversal times vary over time, the Time-Dependent Travelling Salesman Problem amounts to find a Hamiltonian tour of least total duration. In this paper we exploit a new degree of freedom in the Cordeau et al. (2014) speed decomposition. This approach results in a parameterized family of lower bounds. The parameters are chosen by fitting the traffic data. The first model is nonlinear and difficult to solve. Hence, we devise a linearization which gives rise to a compact Mixed Integer Linear Programming model. Then, we develop an optimality condition which allows to further reduce the size of the model. Computational results show that, when embedded into a branch-and-bound procedure, this lower bounding mechanism allows to solve to optimality a larger number of instances than state-of-the-art algorithms
Co-breaking in the bond-equity yield equilibrium model: an empirical analysis for the United States
No full textIn this paper we present estimates indicating that there is a long run equilibrium relationship between the earnings yield on
stocks and the yield on 10-year Treasury bonds and that this equilibrium relationship implies co-breaking with forward earnings
growth. We are also able to show that this co-breaking relationship works in the same way with a variable which has been shown to
relate the variation through time of risk premia to business conditions. Our approach is similar to Krolzig and Toro [2004. Decision
Support Systems 37, 531– 542] who demonstrate that the present value theory implies co-breaking of Bond-Equity Yield Ratio
(BEYR) and dividend growth. In our paper we analyse if this result can be proven also for the so called Fed model, which is a variant
of BEYR. We provide an empirical analysis of the validity of this hypothesis in the United States for the time period 1979.1-2005.8.
Comparing the results with a linear VAR and with alternative formulations of Markov switching VAR (MS-VARX and MS-DVAR),
we find that co-breaking of the bond-equity yield equilibrium ratio and forward earnings growth or a variable that proxy for changes
in risk premium, shows a superior ability to describe bull and bear cycles in the stock market
Supporting orientation for blind people using museum guides
No full textNovel environments exploiting recent technology can enhance several tasks in applications such as mobile guides. However, in the many museum mobile guides that have been proposed, accessibility is often not explicitly addressed and the benefits of such technology are rarely made available to blind users. In this paper, we propose a solution for flexible orientation support in a multimodal and location-aware museum guide, which has been developed specifically for blind users
A composite tourism index for the competitiveness of marginal areas: a pilot application in a Southern Italy province
No full textDifferently from traditional approaches that rely on the analysis of single dimensions of the tourism phenomenon, this study aims to experiment a systemic approach based on structured and unstructured data sources to elaborate a composite index to measure the tourist competitiveness of marginal areas, with the final aim to design and plan proper socio-economic development strategies. The methodology adopted to carry out the study follows a four-step process and relies on indicators that are both relevant and accessible. The first step concerns the analysis of the literature about the existing approaches to calculate a tourism index. The second step concerns the definition of the indicators and the collection of data by using both structured and unstructured sources. The third step focuses on the population of the data set. Finally, the fourth step aims at calculating the tourism index through a composite-based methodology and using it for a pilot application in a Southern Italy province. The study calculates a synthetic tourism index for each of the 97 municipalities of the Province of Lecce (a city located in the southeast of Italy). The proposed index combines administrative, institutional and open data sources to derive a single indicator for each municipality, thus supporting decision-makers in understanding the complex reality and competitiveness level of territories in the tourism industry. The main elements of originality of the study are the breadth and typology of data sources considered to calculate the composite indicator of tourism competitiveness (both structured and unstructured); and the use of weighting and aggregation procedures in the methodological issues
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