Fractional kinetics emerging from ergodicity breaking in random media

We present a modelling approach for diffusion in a complex medium characterized by a random length scale. The resulting stochastic process shows subdiffusion with a behavior in qualitative agreement with single particle tracking experiments in living cells, such as ergodicity breaking, p-variation and aging. In particular, this approach recapitulates characteristic features previously described in part by the fractional Brownian motion and in part by the continuous-time random walk. Moreover, for a proper distribution of the length scale, a single parameter controls the ergodic-to-nonergodic transition and, remarkably, also drives the transition of the diffusion equation of the process from non-fractional to fractional, thus demonstrating that fractional kinetics emerges from ergodicity breaking.Comment: Extended version of arXiv:1508.01361: Gianni Pagnini, Daniel Molina-Garc\'ia, Tuan Minh Pham, Carlo Manzo, Paolo Paradisi, Ergodicity breaking in random media and the foundation of fractional kinetic

Sustainable rice cultivation in the deep flooded zones of the Vietnamese Mekong Delta

This paper explains how the management of the full-dyke system in the deep flooded zones of the Vietnamese Mekong Delta affects rice cultivation, and outlines how alternative dyke management strategies could offer more sustainable adaptations in the face of future environmental threats. The current management of the ‘full-dyke’ network has been successful in promoting triple-cropping rice cultivation, but this practice has prevented sediment deposition on the land surface. River-borne sediments deposited on the delta land surface have high economic value because they are (i) rich in nutrients (potentially 26 million USD/yr of free fertiliser to An Giang Province) and can (ii) help to maintain the Mekong Delta land above sealevel. Without a continuing supply of sediment to the delta, triple-cropping paddies may not continue to be sustainable or profitable for the majority of rice farmers over the next 10 to 20 years. The economic value of sediment as a free fertiliser is particularly important to poor farmers, as without sediment, they run a significant risk of debt due to fluctuations in rice, fertiliser, and other input prices. With incoming loads now declining, sediment must be managed carefully as a resource. Our projections show that the best use of the remaining sediment resource can be achieved by allowing full paddy flooding only in years of high sediment potential, and this would greatly increase the sustainability of rice agriculture in the face of future environmental change. This recommended policy is an option with few regrets, in that its other benefits include maximising groundwater replenishment, ensuring freshwater availability during drought periods (including countering salt water intrusion), cleansing rice paddies of pests and disease, and tempering downstream flooding. If triple-rice-cropping continues to have priority, financial support will particularly be needed to provide help to poorer farmers coping with increases in artificial fertiliser prices

Probabilistic Roadmaps for Aerial Relay Path Planning

Unmanned aerial vehicles (UAVs) with on-board relays can be used to establish multi-hop links that deliver high-speed connectivity beyond cell limits. This is of utmost importance e.g. in remote areas and in emergency scenarios. However, jointly designing the trajectories of multiple such flying relays is a complex task since the dimensionality of the underlying configuration space is too large to allow the direct application of traditional shortest-path methods. To bypass this difficulty, this work proposes a probabilistic roadmap algorithm based on a novel heuristic path design which is guaranteed to provide feasible paths for all UAVs under general conditions. This addresses the limitations of existing algorithms, which are typically based on non-linear optimization and, therefore, entail high complexity and cannot readily accommodate the presence of obstacles such as buildings. As corroborated via numerical experiments in an urban environment, the proposed scheme can establish a high-speed link with a user by means of just two aerial relays in a short time

Acceptance-Promoting Practice Framework for Online Collaborative Learning and EdTech in Formal Education: a Thematic Analysis of Literature

This exploratory quantitative study seeks to identify (a) the e-learning practices that can improve the acceptance of online collaborative learning (OCL) and the associated EdTech in formal learning contexts and (b) the characteristics or features of such EdTech. A systematic review was conducted combined with a thematic analysis of literature (i.e., 42 journal articles relevant to OCL that was published from 2001 to 2020 from Scopus database), the findings of which not only attained all research objectives with the proposed the acceptance-promoting practice framework for OCL and EdTech (APPFOE) in formal education (see Figure 7), but also identified the challenges that OCL learners generally confront. The proposed APPFOE reveals a number of practices in three main themes (viz., teacher presence, OCL EdTech, and learners’ control over learning) that can handle those challenges and promote the acceptance of OCL and the associated EdTech in light of the extended unified theory of acceptance and use of technology model. The implications for positive social change include the potential to guide educators in their class interactions, aid policymakers with their alignment of resources, assist EdTech professionals and entrepreneurs in their product development, and contribute to the growing body of academic knowledge in some respects, hence lay out the basis for some future research