Internet's Critical Path Horizon

Internet is known to display a highly heterogeneous structure and complex fluctuations in its traffic dynamics. Congestion seems to be an inevitable result of user's behavior coupled to the network dynamics and it effects should be minimized by choosing appropriate routing strategies. But what are the requirements of routing depth in order to optimize the traffic flow? In this paper we analyse the behavior of Internet traffic with a topologically realistic spatial structure as described in a previous study (S-H. Yook et al. ,Proc. Natl Acad. Sci. USA, {\bf 99} (2002) 13382). The model involves self-regulation of packet generation and different levels of routing depth. It is shown that it reproduces the relevant key, statistical features of Internet's traffic. Moreover, we also report the existence of a critical path horizon defining a transition from low-efficient traffic to highly efficient flow. This transition is actually a direct consequence of the web's small world architecture exploited by the routing algorithm. Once routing tables reach the network diameter, the traffic experiences a sudden transition from a low-efficient to a highly-efficient behavior. It is conjectured that routing policies might have spontaneously reached such a compromise in a distributed manner. Internet would thus be operating close to such critical path horizon.Comment: 8 pages, 8 figures. To appear in European Journal of Physics B (2004

Logarithmic growth dynamics in software networks

In a recent paper, Krapivsky and Redner (Phys. Rev. E, 71 (2005) 036118) proposed a new growing network model with new nodes being attached to a randomly selected node, as well to all ancestors of the target node. The model leads to a sparse graph with an average degree growing logarithmically with the system size. Here we present compeling evidence for software networks being the result of a similar class of growing dynamics. The predicted pattern of network growth, as well as the stationary in- and out-degree distributions are consistent with the model. Our results confirm the view of large-scale software topology being generated through duplication-rewiring mechanisms. Implications of these findings are outlined.Comment: 7 pages, 3 figures, published in Europhysics Letters (2005

Agallas De Cecidoses Eremita Curtis Y Eucecidoses Minutanus Brèthes (lepidoptera: Cecidosidae) En Magdalena, Prov. De Buenos Aires: Muestreo Preliminar Y Fauna Asociada

In Argentina, five galling species of the family Cecidosidae (Lepidoptera), including Cecidoses eremita Curtis and Eucecidoses minutanus Brèthes, have been cited. This note reports a preliminary study of their galls in "molles" (Schinus longifolius (Lindl.) Speg.) of Magdalena (Buenos Aires, Argentina). In April 2013, galls of C. eremita and E. minutanus were censused in randomly selected "molles". In April and December 2013, randomly selected galls were then collected and transported to our laboratory in hermetic bags, and conserved at -18 °C until examination. Maximum diameter and wall thickness of collected galls were measured. About 84% of the observed "molles" (103/123) had galls of C. eremita and/or E. minutanus. The median of galls per tree was 12 (Q1=6; Q3=22). Eucecidoses minutanus had galls with smaller diameter (U11;53= 583; P<0.05) and thinner wall (U10;52=506.5; P<0..05) than C. eremita. In open galls, we found Pseudoescorpionida, Araneae (Segestriidae and Salticidae), and larvae of Lepidoptera and Hymenoptera. Within closed galls, we found adults of Torymidae and Chalcidoidea, and larvae of Ichneumonoidea. © 2016, Universidade Estadual de Campinas UNICAMP. All rights reserved.16

Analysis of loss of life of dry-type WTSU transformers in offshore wind farms

Currently, dry-type transformers are commonly installed as wind turbine step-up (WTSU) transformers, especially in offshore wind farms. Due to their low flammability and resistance to moisture, their performance is optimal in offshore platforms. Nonetheless, their thermal-electrical degradation must be carefully considered given the special wind and weather conditions in marine environments. The present paper studies the thermal aging of dry-type WTSU transformers in offshore wind farms considering the most thermally stressed location i.e. the winding hot-spot. The estimation of the transformer lifetime consumption introduced in this work can be applied in the framework of digital twins for diagnostic and prognostic monitoring purposes The thermal degradation study is based on a typical offshore load profile and includes the analysis of the impact of several transformer characteristics and operating conditions. As a result of the analysis, it can be concluded that lower temperature insulations, forced air cooling systems, a lower mean winding temperature rise and cool ambient temperatures lead to decreased loss of life values. Also, the present work suggests the suitability of considering thermal degradation studies as an optimal sizing factor for offshore WTSU given the low ambient temperatures in marine environment and the low capacity factors.The authors gratefully acknowledge the Support of the Basque Government (project ELKARTEK KK - 2018/00096 and GISEL research group IT1191-19), as well as of the University of the Basque Country UPV/EHU (research group unding GIU18/181)