Spanning trees with generalized degree constraints arising in the design of wireless networks

In this paper we describe a minimum spanning tree problem with generalized degree constraints which arises in the design of wireless networks. The signal strength on the receiver side of a wireless link decreases with the distance between transmitter and receiver. In order to work properly, the interference on the receiving part of the link must be under a given threshold. In order to guarantee this constraint, for each node we impose a degree constraint that depends on the ”length” of the links adjacent to the corresponding node, more precisely, nodes adjacent to long links must have a smaller degree and vice-versa. The problem is complicated by considering different signal strengths for each link. Increasing the strength in a link increases the cost of the link. However, it also reduces the maximum allowed degree on its end nodes. We create two models using adequate sets of variables, one may be considered an extended version of the other, and relate, from a theoretical perspective, the corresponding linear programming relaxations.FCT - POCTI-ISFL-1-152FCT - PTDC/EIA/64772/200

Large scale railway renewal planning with a multiobjective modeling approach

Conferência realizada na Filândia, Helsinquia, de 20-24 de agosto de 2018A multiobjective modeling approach for managing large scale railway infrastructure asset renewal is presented. An optimized intervention project schedule is obtained considering operational constraints in a three objectives model: evenly spreading investment throughout multiple years, minimizing total cost, minimizing work start postponements on higher priority railway sections. The MILP model was based on a real world case study; the objectives and constraints specified by an infrastructure management company. Results show that investment spreading greatly influences the other objectives and that total cost fluctuations depend on the overall condition of the railway infrastructure. The model can produce exact efficient solutions in reasonable time, even for very large-sized instances (a test network of similar size to the USA railway network, the largest in the world). The modeling approach is therefore a very useful, practical methodology, for generating optimized solutions and analyzing trade-offs among objectives, easing the task of ultimately selecting a solution and produce the works schedule for field implementation.info:eu-repo/semantics/publishedVersio

Bi-objective modeling approach for repairing multiple feature infrastructure systems

A bi-objective decision aid model for planning long-term maintenance of infrastructure systems is presented, oriented to interventions on their constituent elements, with two upgrade levels possible for each element (partial/full repairs). The model aims at maximizing benefits and minimizing costs, and its novelty is taking into consideration, and combining, the system/element structure, volume discounts, and socioeconomic factors. The model is tested with field data from 229 sidewalks (systems) and compared to two simpler repair policies, of allowing only partial or full repairs. Results show that the efficiency gains are greater in the lower mid-range budget region. The proposed modeling approach is an innovative tool to optimize cost/benefits for the various repair options and analyze the respective trade-offs.info:eu-repo/semantics/publishedVersio

Multi-objective model for optimizing railway infrastructure asset renewal

Trabalho inspirado num problema real da empresa Infraestruturas de Portugal, EP.A multi-objective model for managing railway infrastructure asset renewal is presented. The model aims to optimize three objectives, while respecting operational constraints: levelling investment throughout multiple years, minimizing total cost and minimizing work start postponements. Its output is an optimized intervention schedule. The model is based on a case study from a Portuguese infrastructure management company, which specified the objectives and constraints, and reflects management practice on railway infrastructure. The results show that investment levelling greatly influences the other objectives and that total cost fluctuations may range from insignificant to important, depending on the condition of the infrastructure. The results structure is argued to be general and suggests a practical methodology for analysing trade-offs and selecting a solution for implementation.info:eu-repo/semantics/publishedVersio

Of the significance of business relationships

The Industrial Network Theory aims to describe and explain the business relationships and networks in which the focal firm is deeply embedded. One of its major propositions is that business relationships somehow influence, to different extents and over time, the focal firm’s survival. This pertains to the diverse and time-varying significance of business relationships for the focal firm. It has often been implicitly sustained that such significance is strongly related to the role played by business relationships and consequently the relationship outcomes accruing to the focal firm. The logic underlying the relationship significance proposition is outwardly oriented, somewhat overlooking the focal firm’s inside and in particular the conspicuous influence of business relationships on what the focal firm does competently both within and across its vertical boundaries. Arguably, the (predominantly ‘functional’) network-based arguments currently advanced represent a necessary but not sufficient condition for relationship significance. This conceptual paper tentatively suggests that there may be missing a supplementary (essentially internal) explanation supported by Competence-based Theories of the Firm.Industrial Network Theory; relationship significance proposition

Barroso and Goldman Sachs: has the EU regulatory state yielded to big business interests?

The appointment of former President of the European Commission José Manuel Barroso as an adviser at Goldman Sachs has generated criticism in recent weeks, with some observers arguing that it represents a clear conflict of interest. Luís de Sousa writes that Barroso’s appointment highlights the need for more effective conflict of interest standards and clearance procedures for Commissioners, and that failure to establish these standards could undermine public confidence in the EU’s institutions

Challenges to political financing regulation: sound external monitoring/enforcement and sensible internal party accountability

Paper prepared for the international conference Corruption Control in Political Life and the Quality of Democracy: A Comparative Perspective Europe – Latin America, ISCTE, Lisbon, 19-20 May 2005In recent years, governments and legislatures have made an unprecedented effort to improve regulatory systems of political financing which had been perceived by many as fraught with corruption. Some countries have been more sensitive to the problem than others given the nature and extent of occurrences, but the successive waves of reform show how difficult it has been for the political class to arrive at an adequate control response. The reform panorama of the 1990s has been characterised by incremental, short-lived and non-comprehensive articulation of control instruments and monitoring/enforcement shortcomings. The general regulatory context was one of reforming to address scandal and an increasingly discontented public opinion towards parties and their representatives. Despite different national responses and understandings of the major issues of concern, there has equally been a convergence of the type of measures adopted and an increasing cross-country transfer of knowledge about the panoply of instruments available. What this paper will argue, however, is that “similarities” concern more the form rather than the substance of control. The transfer of regulatory instruments has taken place faster than the expected convergence of standards of conduct. Drawing from different regulatory experiences, the article deals with a series of interrelated issues of political financing regulation: liberal versus regulatory approaches to political financing; public versus private modes of political financing; balancing revenue and expenditure; rules of publicity and publication of accounts; making parties accountable internally and externally to monitoring bodies; matching penalties to offences. The aim is to provide a general reflection of the general features of the law and practice of political finance as a preliminary step towards more general conclusions about the challenges facing political financing regulation today. In short, the article attempts to address two overarching questions: Do laws on political financing suffice to constrain party related illegality? Why certain countries do better than others in face of the degree of cross-country transfer of knowledge and regulatory innovation achieved in recent years

Relationship significance: is it sufficiently explained?

The Industrial Networks Theory (cf. Axelsson and Easton, 1992, Hakansson and Snehota, 1995) sets out to describe and explain the business relationships and markets in which the focal firm is deeply embedded. One of its major propositions pertains to the (time-varying) significance of business relationships for the focal firm (Gadde et al., 2003), i.e., business relationships influence to some extent the focal firm’s survival. Such significance seems strongly related to the role played by business relationships and consequently the relationship outcomes accruing to the focal firm. The theoretical justification underlying this proposition is outwardly oriented, somewhat overlooking the inside of the focal firm - in particular the influence of business relationships on what the focal firm does competently within and across its boundaries. Arguably, the creation and appropriation of relationship value by the focal firm is a necessary but not sufficient condition for relationship significance. A supplementary (internal) explanation supported by Knowledge-based Theories of the Firm (e.g., see Kogut and Zander, 1992), we suggest, may be missing. Our aim here has been to intuitively pinpoint a theoretical flaw, further suggesting a feasible path for its solution.Industrial Networks Theory; relationship significance proposition; relationship functions, dysfunctions, benefits, sacrifices, and value

How is the relationship significance brought about? A critical realist approach

The markets-as-networks theorists contend, at least tacitly, the significance of business relationships for the focal firm – that is, business relationships contribute somewhat to the focal firm’s survival and growth. We do not deny the existence of significant business relationships but sustain, in contrast to the consensus within the Markets-as-Networks Theory, that relationship significance should not be a self-evident assumption. Significance cannot be a taken-for-granted property of each and every one of the focal firm’s business relationships. We adopt explicitly a critical realist position in this conceptual paper and claim that the relationship significance is an event of the business world, whose causes remain yet largely unidentified. Where the powers and liabilities of business relationships (i.e., their functions and dysfunctions) are put to work, inevitably under certain contingencies (namely the surrounding networks and markets), effects result for the focal firm (often benefits in excess of sacrifices, i.e., relationship value) and as a result the relationship significance is likely to be brought about. In addition, the relationship significance can result from the dual influence that business relationships have on a great part of the structure and powers and liabilities of the focal firm, i.e., its nature and scope respectively.Markets-as-Networks Theory, relationship significance, business relationships, focal firm, resources, competences, activities