If CPM is so bad, why have we been using it so long?

Why has the Critical Path Method (CPM) been used so widely for so long given its inability to produce predictable outcomes? For shedding light on this paradox, the formative period of the CPM is analysed from two main angles. First, how was the CPM embedded into the construction management practice? Second, what was the methodological underpinning of the development of the CPM? These questions are researched through a literature review. In terms of embeddedness into practice, it turns out that the CPM morphed from being a way of production control, into a method for contract control. In consequence, the promotion of the CPM by owners has been crucial for pushing this method to be the mainstream approach to scheduling and production control. Regarding methodological underpinning, it turns out that the CPM was developed as a way of optimization, as part of the quantitative methods movement. This movement was largely based on the axiomatic approach to research. In good alignment with that approach, there was no attempt to empirically test quantitative models and their outcomes. In this context, the unrealistic assumptions and conceptualizations in CPM did not surface in forty years. These results are argued to be helpful in critical discussions on the role and merits of CPM and on the methodologies to be used in construction management research

The behavior of dealers and clients on the European corporate bond market: the case of Multi-Dealer-to-Client platforms

For the last two decades, most financial markets have undergone an evolution toward electronification. The market for corporate bonds is one of the last major financial markets to follow this unavoidable path. Traditionally quote-driven i.e., dealer-driven) rather than order-driven, the market for corporate bonds is still mainly dominated by voice trading, but a lot of electronic platforms have emerged. These electronic platforms make it possible for buy-side agents to simultaneously request several dealers for quotes, or even directly trade with other buy-siders. The research presented in this article is based on a large proprietary database of requests for quotes (RFQ) sent, through the multi-dealer-to-client (MD2C) platform operated by Bloomberg Fixed Income Trading, to one of the major liquidity providers in European corporate bonds. Our goal is (i) to model the RFQ process on these platforms and the resulting competition between dealers, and (ii) to use our model in order to implicit from the RFQ database the behavior of both dealers and clients on MD2C platforms

Electron impact excitation rates for transitions in Mg V

Energy levels, radiative rates (A-values) and lifetimes, calculated with the GRASP code, are reported for an astrophysically important O-like ion Mg~V. Results are presented for transitions among the lowest 86 levels belonging to the 2s$^2$2p$^4$, 2s2p$^5$, 2p$^6$, and 2s$^2$2p$^3$3$\ell$ configurations. There is satisfactory agreement with earlier data for most levels/transitions, but scope remains for improvement. Collision strengths are also calculated, with the DARC code, and the results obtained are comparable for most transitions (at energies above thresholds) with earlier work using the DW code. In thresholds region, resonances have been resolved in a fine energy mesh to determine values of effective collision strengths ($\Upsilon$) as accurately as possible. Results are reported for all transitions at temperatures up to 10$^6$~K, which should be sufficient for most astrophysical applications. However, a comparison with earlier data reveals discrepancies of up to two orders of magnitude for over 60\% of transitions, at all temperatures. The reasons for these discrepancies are discussed in detail.Comment: 11p of Text, 6 Tables and 6 Figures will appear in Canadian J. Physics (2017

The categorical limit of a sequence of dynamical systems

Modeling a sequence of design steps, or a sequence of parameter settings, yields a sequence of dynamical systems. In many cases, such a sequence is intended to approximate a certain limit case. However, formally defining that limit turns out to be subject to ambiguity. Depending on the interpretation of the sequence, i.e. depending on how the behaviors of the systems in the sequence are related, it may vary what the limit should be. Topologies, and in particular metrics, define limits uniquely, if they exist. Thus they select one interpretation implicitly and leave no room for other interpretations. In this paper, we define limits using category theory, and use the mentioned relations between system behaviors explicitly. This resolves the problem of ambiguity in a more controlled way. We introduce a category of prefix orders on executions and partial history preserving maps between them to describe both discrete and continuous branching time dynamics. We prove that in this category all projective limits exist, and illustrate how ambiguity in the definition of limits is resolved using an example. Moreover, we show how various problems with known topological approaches are now resolved, and how the construction of projective limits enables us to approximate continuous time dynamics as a sequence of discrete time systems.Comment: In Proceedings EXPRESS/SOS 2013, arXiv:1307.690

Coupled systems of fractional equations related to sound propagation: analysis and discussion

In this note we analyse the propagation of a small density perturbation in a one-dimensional compressible fluid by means of fractional calculus modelling, replacing thus the ordinary time derivative with the Caputo fractional derivative in the constitutive equations. By doing so, we embrace a vast phenomenology, including subdiffusive, superdiffusive and also memoryless processes like classical diffusions. From a mathematical point of view, we study systems of coupled fractional equations, leading to fractional diffusion equations or to equations with sequential fractional derivatives. In this framework we also propose a method to solve partial differential equations with sequential fractional derivatives by analysing the corresponding coupled system of equations