Dynamic Modeling of the Electric Transportation Network

We introduce a model for the dynamic self-organization of the electric grid. The model is characterized by a conserved magnitude, energy, that can travel following the links of the network to satisfy nodes' load. The load fluctuates in time causing local overloads that drive the dynamic evolution of the network topology. Our model displays a transition from a fully connected network to a configuration with a non-trivial topology and where global failures are suppressed. The most efficient topology is characterized by an exponential degree distribution, in agreement with the topology of the real electric grid. The model intrinsically presents self-induced break-down events, which can be thought as representative of real black-outs.Comment: (e.g. 7 pages, 5 figures

Emergence and criticality in spatiotemporal synchronization: the complementarity model

This work concerns the long-term dynamics of a spatiotemporal many-body deterministic model that exhibits emergence and self-organization, and which has been recently proposed as a new paradigm for Artificial Life. Collective structures emerge in the form of dynamic networks, created by bursts of spatiotemporal activity (avalanches) at the edge of a synchronization phase transition. The spatiotemporal dynamics is portraited by a motion picture and quantified by time varying collective parameters, which revealed that the dynamic networks undergo a "life cycle", made of self-creation, self-regulation, and self-destruction. The power spectra of the collective parameters show 1/f power-law tails, and the statistical properties of the avalanches, evaluated in terms of their size and durations, show power laws with characteristic exponents in agreement with those values found in the literature concerning neural networks. The mechanism underlying avalanches is discussed in terms of local-to-collective excitability. Finally, the connections that link the present work to self-organized criticality, neural networks and artificial life are discussed

A mesoscopic model for the collective dynamics of water coherence domains

This work deals with a mesoscopic and deterministic theory for the collective dynamics of Water Coherence Domains, and it represents a continuation of a previous work published in Plos ONE https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0188753 This approach qualitatively reproduces some features of the experimental phenomenology, and it could sustain an evolutionary theory based on layered synchronization processes. Its relevance for the description of the processes behind the emergence of life is discussed

Managing uncertainty in regional supply chains: The case of Fresh fruit from Lleida province

Supply chain management typically examines a network of companies from production to consumption with the aim to improve performance in terms of cost. During the last decades, supply chain management has evolved to include multi-objective performance measurement goals such as flexibility, reliability, and recently sustainability. In food supply chains sustainability is measured with CO2 emissions and other environmental indicators. However, there are two gaps in our understanding of managing supply chains effectively. Firstly, uncertainty is a key factor that influences the performance of chains. Although, scholars such as van der Vorst and Beulens (2002) have early identified uncertainty as a key parameter in supply chains, there is little empirical evidence on how to model it effectively. This is surprising since supply chains are prone to complexity and uncertainty. Therefore, making well-informed supply chain decisions requires risk analysis, control and mitigation (Heckmann, 2015). According to van der Vorst and Beulens (2002), there are three characteristics of supply chain uncertainty: - Inherent characteristics: variability in demand, supply or process are extremely common in perishable product chains. - Chain characteristics: chain configuration, such consolidation points, may disturb the system. - Exogenous phenomena: they are not controllable by the firm. This category includes weather conditions, governmental regulations, etc. Solutions to such increasing inventory, adding capacity at different locations and having multiple suppliers — undermine efforts to improve supply chain cost efficiency (Sunil, 2014) The second gap in our understanding food supply chains lies on the methods applied where the unit of analysis is usually the firm-level or in fewer studies the dyad between suppliers and retailers. Only but few studies, have examined the region as unit of analysis in food supply chains (Soysal et al. 2014) This study aimed to examine the regional supply chains and assess how uncertainly affects their performance. The method was a case study of Fresh fruit from Lleida province. Data collection included site visits, interviews with key managers and secondary data sources. The study modeled the fruit supply chains from Lleida to EU destinations. It analyses the key risk factors that influence decision making. The study sheds light how regions compete in global supply chains which is significant especially after the Brexit outcome. A number of recommendations and suggestions for further research are also provided. References Heckmann, Iris, Tina Comes, and Stefan Nickel. (2015), A critical review on supply chain risk–Definition, measure and modelling, Omega, Vol 52, No. 119-132. Soysal, M., Bloemhof-Ruwaard, J. and van der Vorst, J. (2014). Modelling food logistics networks with emission considerations: The case of an international beef supply chain. International Journal of Production Economics, Vol. 152, pp.57-70. van der Vorst, J. and Beulens, A. (2002). Identifying sources of uncertainty to generate supply chain redesign strategies. International Journal of Physical Distribution & Logistics Management, Vol. 32, No. 6, pp.409-430

Functional fatigue of NiTi Shape Memory wires for a range of end loadings and constraints

The availability of engineering strength data on shape memory alloys (SMAs) under cyclic thermalactivation (functional fatigue) is central to the rational design of smart actuators based on these materials. Testresults on SMAs under functional fatigue are scarce in the technical literature and the few data available aremainly limited to constant-stress loading. Since the SMA elements used within actuators are normally biased byelastic springs or by another SMA element, their stress state is far from constant in operation. The mismatchbetween actual working conditions and laboratory arrangements leads to suboptimal designs and underminesthe prediction of the actuator lifetime. This paper aims at bridging the gap between experiment and reality. Fourtest procedures are planned, covering most of the typical situations occurring in practice: constant-stress,constant-strain, constant-stress with limited maximum strain and linear stress-strain variation with limitedmaximum strain. The paper describes the experimental apparatus specifically designed to implement the fourloading conditions and presents fatigue results obtained from commercial NiTi wires tested under all thoseprotocols

The emergence of dynamic networks from many coupled polar oscillators. A model for Artificial Life

This work concerns a many-body deterministic model that displays life-like properties as emergence, complexity, self-organization, spontaneous compartmentalization, and self-regulation. The model portraits the dynamics of an ensemble of locally coupled polar phase oscillators, moving in a two-dimensional space, that in certain conditions exhibit emergent superstructures. Those superstructures are self-organized dynamic networks, resulting from a synchronization process of many units, over length scales much greater than the interaction length. Such networks compartmentalize the two-dimensional space with no a priori constraints, due to the formation of porous transport walls, and represent a highly complex and novel non-linear behavior. The analysis is numerically carried out as a function of a control parameter showing distinct regimes: static, stable dynamic networks, intermittency, and chaos. A statistical analysis is drawn to determine the control parameter ranges for the various behaviors to appear.Comment: 14 pages, 8 figures and 4 movie

Functional fatigue of shape memory wires under constant-stress and constant-strain loading conditions

Abstract Shape memory alloys (SMAs) are increasingly used for the construction of simple solid-state actuators characterized by outstanding power density. The rational design of these actuators requires reliable data on the fatigue strength of the alloy under cyclic thermal activation (functional fatigue). The technical literature shows scanty test results for SMAs under functional fatigue. Furthermore, the few data available are mainly limited to the condition of constant stress applied to the material. Sincethe SMA elements used within actuators are normally biased by conventional springs or by another SMA element, their stress condition is far from constant in operation. The disagreement between actual working conditions and laboratory conditions leadsto suboptimal designs and undermines the prediction of the life of the actuator. This paper aims at bridging the gap between experiment and reality. Four characteristic test conditions are envisioned, covering most of the actual situations occurring inpractice: constant-stress, constant-strain, constant-stress with controlled maximum strain and cyclic-stress with controlled maximum strain. The paper presents the experimental apparatus specifically designed to implement the four test conditions. Fatigue results on a commercial NiTi wire (0.15 mm diameter) tested under constant-stress and constant-strain loading are also presented and discussed

Carbon supported bimetallic Ru‐Co catalysts for H2 production through NaBH4 and NH3BH3 hydrolysis

Summary This work investigates the effect of the addition of small amounts of Ru (0.5-1 wt%) to carbon supported Co (10 wt%) catalysts towards both NaBH4 and NH3BH3 hydrolysis for H2 production. In the sodium borohydride hydrolysis, the activity of Ru-Co/carbon catalysts was sensibly higher than the sum of the activities of corresponding monometallic samples, whereas for the ammonia borane hydrolysis, the positive effect of Ru-Co systems with regard to catalytic activity was less evident. The performances of Ru-Co bimetallic catalysts correlated with the occurrence of an interaction between Ru and Co species resulting in the formation of smaller ruthenium and cobalt oxide particles with a more homogeneous dispersion on the carbon support. It was proposed that Ru°, formed during the reduction step of the Ru-Co catalysts, favors the H2 activation, thus enhancing the reduction degree of the cobalt precursor and the number of Co nucleation centers. A subsequent reduction of cobalt and ruthenium species also occurs in the hydride reaction medium, and therefore the state of the catalyst before the catalytic experiment determines the state of the active phase formed in situ. The different relative reactivity of the Ru and Co active species towards the two investigated reactions accounted for the different behavior towards NaBH4 and NH3BH3 hydrolysis