Effects of circular measures on scarce metals in complex products – Case studies of electrical and electronic equipment

Circular measures such as long-life designs, reuse, repair and recycling have been suggested for prolonging scarce metal life cycles and reducing the dependence on primary resources. This paper explores to what extent circular measures could mitigate metals scarcity when adopted to complex products. Based on three real cases, the effect of extending the use of laptops, smartphones and LED systems before recycling are assessed for between 7 and 15 scarce metals using material flow analysis. As expected, benefits can be gained from such extensions, but, importantly, differ substantially between metals since they occur in various components with various service lifetimes and functional recycling rates vary. Notably, risks of flipping the ranking in favor of short use before recycling are identified: if service lifetimes are short, designs are metal-intensive or if metal contents differ between products. Furthermore, regardless of measure, sizable and varying losses of each metal from functional use occur since all products are not collected for recycling and all metals are not functionally recycled. Thus, neither use extension measures nor recycling can alone nor in combination radically mitigate metals scarcity and criticality currently. Overall, it is a challenge to target the multitude of scarce and critical metals applied in complex products through circular measures. Careful analysis beyond simplified guidelines such as \uf6R frameworks” are recommended. As the importance of scarce metals availability and the attention to the circular economy are expected to continue, these insights may be used for avoiding efforts with unclear or minor benefits or even drawbacks

Multivariate Granger Causality and Generalized Variance

Granger causality analysis is a popular method for inference on directed interactions in complex systems of many variables. A shortcoming of the standard framework for Granger causality is that it only allows for examination of interactions between single (univariate) variables within a system, perhaps conditioned on other variables. However, interactions do not necessarily take place between single variables, but may occur among groups, or "ensembles", of variables. In this study we establish a principled framework for Granger causality in the context of causal interactions among two or more multivariate sets of variables. Building on Geweke's seminal 1982 work, we offer new justifications for one particular form of multivariate Granger causality based on the generalized variances of residual errors. Taken together, our results support a comprehensive and theoretically consistent extension of Granger causality to the multivariate case. Treated individually, they highlight several specific advantages of the generalized variance measure, which we illustrate using applications in neuroscience as an example. We further show how the measure can be used to define "partial" Granger causality in the multivariate context and we also motivate reformulations of "causal density" and "Granger autonomy". Our results are directly applicable to experimental data and promise to reveal new types of functional relations in complex systems, neural and otherwise.Comment: added 1 reference, minor change to discussion, typos corrected; 28 pages, 3 figures, 1 table, LaTe

Representation of complex probabilities and complex Gibbs sampling

Complex weights appear in Physics which are beyond a straightforward importance sampling treatment, as required in Monte Carlo calculations. This is the well-known sign problem. The complex Langevin approach amounts to effectively construct a posi\-tive distribution on the complexified manifold reproducing the expectation values of the observables through their analytical extension. Here we discuss the direct construction of such positive distributions paying attention to their localization on the complexified manifold. Explicit localized repre\-sentations are obtained for complex probabilities defined on Abelian and non Abelian groups. The viability and performance of a complex version of the heat bath method, based on such representations, is analyzed.Comment: Proceedings of Lattice 2017 (The 35th International Symposium on Lattice field Theory). 8 pages, 4 figure

Online korean skincare decision support system

Despite the explosive growth of electronic commerce and the rapidly increasing number of consumers who use interactive media for pre-purchase information search and online shopping, very little is known about how consumers make purchase decisions in such settings. One desirable form of interactivity from a consumer perspective is the implementation of sophisticated tools to assist shoppers in their purchase decisions by customizing the electronic shopping environment to their individual preferences

Graph Metrics for Temporal Networks

Temporal networks, i.e., networks in which the interactions among a set of elementary units change over time, can be modelled in terms of time-varying graphs, which are time-ordered sequences of graphs over a set of nodes. In such graphs, the concepts of node adjacency and reachability crucially depend on the exact temporal ordering of the links. Consequently, all the concepts and metrics proposed and used for the characterisation of static complex networks have to be redefined or appropriately extended to time-varying graphs, in order to take into account the effects of time ordering on causality. In this chapter we discuss how to represent temporal networks and we review the definitions of walks, paths, connectedness and connected components valid for graphs in which the links fluctuate over time. We then focus on temporal node-node distance, and we discuss how to characterise link persistence and the temporal small-world behaviour in this class of networks. Finally, we discuss the extension of classic centrality measures, including closeness, betweenness and spectral centrality, to the case of time-varying graphs, and we review the work on temporal motifs analysis and the definition of modularity for temporal graphs.Comment: 26 pages, 5 figures, Chapter in Temporal Networks (Petter Holme and Jari Saram\"aki editors). Springer. Berlin, Heidelberg 201