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Aims. We study the ensemble X-ray variability properties of active galactic nuclei (AGN) over large ranges of timescale (20 ks ≤  T  ≤ 14 yr), redshift (0 ≤  z  ≲ 3), luminosity (10 40  erg s −1  ≤  L X  ≤ 10 46  erg s −1 ), and black hole (BH) mass (10 6  ≤  M ⊙  ≤ 10 9 ). Methods. We propose the use of the variance-frequency diagram as a viable alternative to the study of the power spectral density (PSD), which is not yet accessible for distant, faint, and/or sparsely sampled AGN. Results. We show that the data collected from archival observations and previous literature studies are fully consistent with a universal PSD form, which does not show any evidence for systematic evolution of shape or amplitude with redshift or luminosity, even if there may be differences between individual AGN at a given redshift or luminosity. We find new evidence that the PSD bend frequency depends on BH mass and possibly on accretion rate. We finally discuss the implications for current and future AGN population and cosmological studies. 

The rapid increase in the wind energy sector has brought forward a challenging problem of disposing off a huge quantity of non-biodegradable, thermosetting fibre reinforced polymer (FRP) composite materials used in wind turbine blades. Most of the existing solutions are either not sustainable or not economical. This study focuses on re-use options. In this paper a design option for re-using decommissioned wind turbine blades in pedestrian bridges is presented. To demonstrate the concept, an 8.5 m long pedestrian bridge is designed using parts taken from two A29 (modified version of Vestas V27) windblades. A preliminary code-based structural analysis is carried out to assess practicality of the proposed design and to check strength and serviceability requirements given in the prescribed codes. The results show that proposed design full-fills the strength criteria and serviceability requirements recommended in the Eurocodes. The maximum strength utilisation of the blade components is found about 61% and deflection is limited to span/303. 

Content Distribution Networks (CDNs) manage their own caching or routing overlay networks to provide reliable and efficient content delivery services. Currently, CDNs have become one of the most important tools on the Internet. They have been responsible for the majority of today's Internet traffic. The performance of CDNs directly influences the experiences of end users. In this paper, we develop several analyses to figure out the key factors influencing the overall performance of a CDN. The primary results demonstrate that the caching overlays and the routing overlays both have their own influential factors affecting CDN performance. Our results also show that the transmission latency between a surrogate and a content owner is a critical factor determining the overall performance of routing overlays. Furthermore, we argue that the surrogate assignment policy of a routing overlay need to seriously take this latency into account. Our analysis results provide a context for the CDN community on preferable surrogate assignment solutions. 

It is critical in social network analysis to understand the underlying mechanisms of online information diffusion. Although there has been much progress on the influential factors that lead to online viral diffusion, little is known about the impact by public opinion. In this paper, we examine the relations between the public opinion among information propagators and the virality of online diffusion based on a large-scale real-world dataset. We propose a set of new metrics for public opinion in online diffusion to reveal their correlation with diffusion structural virality, and further apply our understanding to predict diffusion virality based on public opinion. The experimental results show the effectiveness of the proposed analysis in the prediction of viral diffusion events.