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

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

Predictors and outcomes of sustained, intermittent or never achieving remission in patients with recent onset inflammatory polyarthritis:Results from the Norfolk Arthritis Register

Objectives: Early remission is the current treatment strategy for patients with inflammatory polyarthritis (IP) and RA. Our objective was to identify baseline factors associated with achieving remission: sustained (SR), intermittent (IR) or never (NR) over a 5-year period in patients with early IP.  Methods: Clinical and demographic data of patients with IP recruited to the Norfolk Arthritis Register (NOAR) were obtained at baseline and years 1, 2, 3 and 5. Remission was defined as no tender or swollen joints (out of 51). Patients were classified as NR or PR, respectively, if they were in remission at: no assessment or ⩾3 consecutive assessments after baseline, and IR otherwise. Ordinal regression and a random effects model, respectively, were used to examine the association between baseline factors, remission group and HAQ scores over time.  Results: A total of 868 patients (66% female) were included. Of these, 54%, 34% and 12% achieved NR, IR and SR, respectively. In multivariate analysis, female sex (odds ratio, OR 0.47, 95% CI: 0.35, 0.63), higher tender joint count (OR = 0.94, 95% CI: 0.93, 0.96), higher HAQ (OR = 0.59, 95% CI: 0.48, 0.74), being obese (OR = 0.70, 95% CI: 0.50, 0.99), hypertensive (OR = 0.67, 95% CI: 0.50, 0.90) or depressed (OR = 0.74, 95% CI: 0.55, 1.00) at baseline were independent predictors of being in a lower remission group. IR and SR were associated with lower HAQ scores over time and lower DAS28 at year 5.  Conclusion: Women with higher tender joint count and disability at baseline, depression, obesity and hypertension were less likely to achieve remission. This information could help when stratifying patients for more aggressive therapy

Ultrasound in the diagnosis of calcium pyrophosphate dihydrate deposition disease. A systematic literature review and a meta-analysis

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Phase Synchronization and Polarization Ordering of Globally-Coupled Oscillators

We introduce a prototype model for globally-coupled oscillators in which each element is given an oscillation frequency and a preferential oscillation direction (polarization), both randomly distributed. We found two collective transitions: to phase synchronization and to polarization ordering. Introducing a global-phase and a polarization order parameters, we show that the transition to global-phase synchrony is found when the coupling overcomes a critical value and that polarization order enhancement can not take place before global-phase synchrony. We develop a self-consistent theory to determine both order parameters in good agreement with numerical results

Emergence of hierarchical networks and polysynchronous behaviour in simple adaptive systems

We describe the dynamics of a simple adaptive network. The network architecture evolves to a number of disconnected components on which the dynamics is characterized by the possibility of differently synchronized nodes within the same network (polysynchronous states). These systems may have implications for the evolutionary emergence of polysynchrony and hierarchical networks in physical or biological systems modeled by adaptive networks.Comment: 4 pages, 4 figure