Creation of models for calculation of coefficients of terrain passability

Quality & Quantity - The content of this article is a paper about a complex mathematical model of terrain passability which respects geographical and meteorological conditions in terrain and...     

Cointegrated TFP processes and international business cycles

A puzzle in international macroeconomics is that real exchange rates are highly volatile. Standard international real business cycle (IRBC) models cannot reproduce this fact. This paper provides evidence that TFP processes for the U.S. and the “rest of the world” are characterized by a vector error correction model (VECM) and that adding cointegrated technology shocks to the standard IRBC model helps to explain the observed high real exchange rate volatility. Also, the model can explain the observed increase in real exchange rate volatility with respect to output in the last 20 years by changes in the parameters of the VECM.     

Migrant Remittances Provide Resilience Against Disasters in Africa

How responsive are migrant remittances to various disasters, both natural and human-made? Would remittances be affected by systemic financial crises, such as the 2008–09 financial crisis, or more recent crises affecting the Eurozone? Using panel data on 23 sub-Saharan African (SSA) countries from 1980 to 2007, we find that remittances are slow to respond to natural disasters, unresponsive to outbreaks of conflict, and will slowly decline following a systemic financial crisis. This suggests that, given its stability, remittances are sources of resilience in SSA.     

Visual displays: analytical study and applications to graphs and real data

Principal axis methods such as principal component analysis (PCA) and correspondence analysis (CA) are useful for identifying structures in data through interesting planar graphic displays. However, some kinds of data sets can be dealt alternatively with PCA or CA. This paper focuses on methods, such as PCA and CA, and on visual displays. Our aim is to illustrate the implications for a potential user of selecting either method, and its advantages and disadvantages, from an applied point of view. This is a matter covered broadly in textbooks and elsewhere considering theoretical arguments. Our purpose is to contribute to the comparison between these methods, over the same data set, in order to illustrate them for the practitioner. In the first part of this paper we present a novel analytical study of a binary matrix associated with a non-oriented axis-symmetric graph and show that CA outperforms standardized PCA for the reconstitution and visualization of such kind of graphs. In the second part we present a case using real data dealing with the distribution of employees in different economic sectors for the countries of the European Union, analyzed by means of standardized PCA and two-way CA, in order to see the differences between the two methods in practice.     

Value-in-context in crowdfunding ecosystems: how context frames value co-creation

The aim of this paper is to analyse the phenomenon of crowdfunding and determine whether it can be considered a service ecosystem, where the context frames innovation through value co-creation. A qualitative, multiple case study approach is used to analyse three platforms and six initiatives in the Spanish arts sector. The findings reveal that crowdfunding can be considered an ecosystem where value-in-context frames seven types of value co-creation, offering a contribution both to ecosystem theory and to the field of co-creation.     

ASSESSING THE EFFECT OF PUBLIC SUBSIDIES ON FIRM R&D INVESTMENT: A SURVEY

This survey examines the empirical literature on the relationship between public R&D subsidies and private R&D investment over the past five decades. The survey reveals a considerable heterogeneity of empirical results that cannot be explained fully by methodological issues. We aim to provide further explanations of the possible causes of that heterogeneity. In particular, we emphasise a set of issues that, in our view, are critical to understanding the potential effect of public R&D subsidies on private R&D spending. Special attention is paid to the dynamic aspects and composition of firm R&D, the constraints faced by the firm (such as financial constraints), and the amount and source of public subsidies. None of these issues have been investigated in depth. We formulate a set of research assumptions to guide future empirical research in this field.     

Multi-product capacitated facility location problem with general production and building costs

This research introduces the multi-product capacitated facility location problem with general production and building costs (MP-CFLPGC). The MP-CFLPGC extends previous problems found in the literature by including multiple products and general production and building cost functions that allow the modeling of different behaviors like economies of scale and congestion. The MP-CFLPGC is formulated as a mixed integer linear program (MILP). To evaluate the performance of the proposed formulation we analyze the results of a commercial optimizer on a set of 288 randomly generated test instances that resemble the Colombian cement industry supply chain. After one hour the optimizer achieved an optimality gap of 1.0 % or less in 55 % out of the 288 test instances. On average the optimality gap was 3.57 %. Additionally, we propose a randomized mathematical-programming-based heuristic for the test instances where the MILP formulation presents significantly high optimality gaps.