Teachers’ primary concerns in a case of educational innovation introduction in primary schools in Greece

By converting all-day primary schools of suburban and urban areas in Greece into schools that implement the Comprehensive Reformed Educational Programme (CREP), a set of innovations were implemented, significantly altering the Greek school. The purpose of this study was to investigate the effect of selected variables over concerns of teachers who work at such schools. Additionally, this research asked the teachers to identify the professional development support and interventions required to enable them to make better use of the Book-reading Advancement (Philanagnosia) Activities innovation. Teachers’ administrative and pedagogical guidance executives, based on the above, will design the necessary interventions to positively address teachers’ concerns and implement the specific innovation in the most effective manner. Overall, the study found that higher teacher concerns were task related, with a significant record of information and self-concerns, which may indicate that the introduction of the innovation was not properly designed to address teachers’ primary concerns

Protection and fault location schemes suited to large-scale multi-vendor high voltage direct current grids

Recent developments in voltage source converter (VSC) technology have led to an increased interest in high voltage direct current (HVDC) transmission to support the integration of massive amounts of renewable energy sources (RES) and especially, offshore wind energy. VSC-based HVDC grids are considered to be the natural evolution of existing point-to-point links and are expected to be one of the key enabling technologies towards expediting the integration and better utilisation of offshore energy, dealing with the variable nature of RES, and driving efficient energy balance over wide areas and across countries. Despite the technological advancements and the valuable knowledge gained from the operation of the already built multi-terminal systems, there are several outstanding issues that need to be resolved in order to facilitate the deployment of large-scale meshed HVDC grids. HVDC protection is of utmost importance to ensure the necessary reliability and security of HVDC grids, yet very challenging due to the fast nature of development of DC faults and the abrupt changes they cause in currents and voltages that may damage the system components. This situation is further exacerbated in highly meshed networks, where the effects of a DC fault on a single component (e.g. DC cable) can quickly propagate across the entire HVDC grid. To mitigate the effect of DC faults in large-scale meshed HVDC grids, fast and fully selective approaches using dedicated DC circuit breaker and protection relays are required. As the speed of DC fault isolation is one order of magnitude faster than typical AC protection (i.e. less than 10 ms), there is a need for the development of innovative approaches to system protection, including the design and implementation of more advanced protection algorithms. Moreover, in a multi-vendor environment (in which different or the same type of equipment is supplied by various manufacturers), the impact of the grid elements on the DC fault signature may differ considerably from case to case, thus increasing the complexity of designing reliable protection algorithms for HVDC grids. Consequently, there is a need for a more fundamental approach to the design and development of protection algorithms that will enable their general applicability. Furthermore, following successful fault clearance, the next step is to pinpoint promptly the exact location of the fault along the transmission medium in an effort to expedite inspection and repair time, reduce power outage time and elevate the total availability of the HVDC grid. Successful fault location becomes increasingly challenging in HVDC grids due to the short time windows between fault inception and fault clearance that limit the available fault data records that may be utilised for the execution of fault location methods. This thesis works towards the development of protection and fault location solutions, designed specifically for application in large-scale multi-vendor HVDC grids. First, a methodology is developed for the design of travelling wave based non-unit protection algorithms that can be easily configured for any grid topology and parameters. Second, using this methodology, a non-unit protection algorithm based on wavelet transform is developed that ensures fast, discriminative and enhanced protection performance. Besides offline simulations, the efficacy of the wavelet transform based algorithm is also demonstrated by means of real-time simulation, thereby removing key technical barriers that have impeded the use of wavelet transform in practical protection applications. Third, in an effort to reinforce the technical and economic feasibility of future HVDC grids, a thorough fault management strategy is presented for systems that employ efficient modular multilevel converters with partial fault tolerant capability. Finally, a fault location scheme is developed for accurately estimating the fault location in HVDC grids that are characterised by short post-fault data windows due to the utilisation of fast acting protection systems.Recent developments in voltage source converter (VSC) technology have led to an increased interest in high voltage direct current (HVDC) transmission to support the integration of massive amounts of renewable energy sources (RES) and especially, offshore wind energy. VSC-based HVDC grids are considered to be the natural evolution of existing point-to-point links and are expected to be one of the key enabling technologies towards expediting the integration and better utilisation of offshore energy, dealing with the variable nature of RES, and driving efficient energy balance over wide areas and across countries. Despite the technological advancements and the valuable knowledge gained from the operation of the already built multi-terminal systems, there are several outstanding issues that need to be resolved in order to facilitate the deployment of large-scale meshed HVDC grids. HVDC protection is of utmost importance to ensure the necessary reliability and security of HVDC grids, yet very challenging due to the fast nature of development of DC faults and the abrupt changes they cause in currents and voltages that may damage the system components. This situation is further exacerbated in highly meshed networks, where the effects of a DC fault on a single component (e.g. DC cable) can quickly propagate across the entire HVDC grid. To mitigate the effect of DC faults in large-scale meshed HVDC grids, fast and fully selective approaches using dedicated DC circuit breaker and protection relays are required. As the speed of DC fault isolation is one order of magnitude faster than typical AC protection (i.e. less than 10 ms), there is a need for the development of innovative approaches to system protection, including the design and implementation of more advanced protection algorithms. Moreover, in a multi-vendor environment (in which different or the same type of equipment is supplied by various manufacturers), the impact of the grid elements on the DC fault signature may differ considerably from case to case, thus increasing the complexity of designing reliable protection algorithms for HVDC grids. Consequently, there is a need for a more fundamental approach to the design and development of protection algorithms that will enable their general applicability. Furthermore, following successful fault clearance, the next step is to pinpoint promptly the exact location of the fault along the transmission medium in an effort to expedite inspection and repair time, reduce power outage time and elevate the total availability of the HVDC grid. Successful fault location becomes increasingly challenging in HVDC grids due to the short time windows between fault inception and fault clearance that limit the available fault data records that may be utilised for the execution of fault location methods. This thesis works towards the development of protection and fault location solutions, designed specifically for application in large-scale multi-vendor HVDC grids. First, a methodology is developed for the design of travelling wave based non-unit protection algorithms that can be easily configured for any grid topology and parameters. Second, using this methodology, a non-unit protection algorithm based on wavelet transform is developed that ensures fast, discriminative and enhanced protection performance. Besides offline simulations, the efficacy of the wavelet transform based algorithm is also demonstrated by means of real-time simulation, thereby removing key technical barriers that have impeded the use of wavelet transform in practical protection applications. Third, in an effort to reinforce the technical and economic feasibility of future HVDC grids, a thorough fault management strategy is presented for systems that employ efficient modular multilevel converters with partial fault tolerant capability. Finally, a fault location scheme is developed for accurately estimating the fault location in HVDC grids that are characterised by short post-fault data windows due to the utilisation of fast acting protection systems

The troubled journey of QoS: From ATM to content networking, edge-computing and distributed internet governance

Network Quality of Service (QoS) and the associated user Quality of Experience (QoE) have always been the networking “holy grail” and have been sought after through various different approaches and networking technologies over the last decades. Despite substantial amounts of effort invested in the area, there has been very little actual deployment of mechanisms to guarantee QoS in the Internet. As a result, the Internet is largely operating on a “best effort” basis in terms of QoS. Here, we attempt a historical overview in order to better understand how we got to the point where we are today and consider the evolution of QoS/QoE in the future. As we move towards more demanding networking environments where enormous amounts of data is produced at the edge of the network (e.g., from IoT devices), computation will also need to migrate to the edge in order to guarantee QoS. In turn, we argue that distributed computing at the edge of the network will inevitably require infrastructure decentralisation. That said, trust to the infrastructure provider is more difficult to guarantee and new components need to be incorporated into the Internet landscape in order to be able to support emerging applications, but also achieve acceptable service quality. We start from the first steps of ATM and related IP-based technologies, we consider recent proposals for content-oriented and Information-Centric Networking, mobile edge and fog computing, and finally we see how distributed Internet governance through Distributed Ledger Technology and blockchains can influence QoS in future networks

Proof-of-Prestige: A Useful Work Reward System for Unverifiable Tasks

As cryptographic tokens and altcoins are increasingly being built to serve as utility tokens, the notion of useful work consensus protocols, as opposed to number-crunching PoW consensus, is becoming ever more important. In such contexts, users get rewards from the network after they have carried out some specific task useful for the network. While in some cases the proof of some utility or service can be proved, the majority of tasks are impossible to verify. In order to deal with such cases, we design Proof-of-Prestige (PoP) - a reward system that can run on top of Proof-of-Stake blockchains. PoP introduces prestige which is a volatile resource and, in contrast to coins, regenerates over time. Prestige can be gained by performing useful work, spent when benefiting from services and directly translates to users minting power. PoP is resistant against Sybil and Collude attacks and can be used to reward workers for completing unverifiable tasks, while keeping the system free for the end-users. We use two exemplar use-cases to showcase the usefulness of PoP and we build a simulator to assess the cryptoeconomic behaviour of the system in terms of prestige transfer between nodes.Comment: 2019 IEEE International Conference on Blockchain and Cryptocurrency (ICBC 2019

NFaaS: Named Function as a Service

In the past, the Information-centric networking (ICN) community has focused on issues mainly pertaining to traditional content delivery (e.g., routing and forwarding scalability, congestion control and in-network caching). However, to keep up with future Internet architectural trends the wider area of future Internet paradigms, there is a pressing need to support edge/fog computing environments, where cloud functionality is available more proximate to where the data is generated and needs processing. With this goal in mind, we propose Named Function as a Service (NFaaS), a framework that extends the Named Data Networking architecture to support in-network function execution. In contrast to existing works, NFaaSbuilds on very lightweight VMs and allows for dynamic execution of custom code. Functions can be downloaded and run by any node in the network. Functions can move between nodes according to user demand, making resolution of moving functions a first-class challenge. NFaaSincludes a Kernel Store component, which is responsible not only for storing functions, but also for making decisions on which functions to run locally. NFaaSincludes a routing protocol and a number of forwarding strategies to deploy and dynamically migrate functions within the network. We validate our design through extensive simulations, which show that delay-sensitive functions are deployed closer to the edge, while less delay-sensitive ones closer to the core

Revisiting Resource Pooling: The Case for In-Network Resource Sharing.

We question the widely adopted view of in-network caches acting as temporary storage for the most popular content in Information-Centric Networks (ICN). Instead, we propose that in-network storage is used as a place of temporary custody for incoming content in a store and forward manner. Given this functionality of in-network storage, senders push content into the network in an open-loop manner to take advantage of underutilised links. When content hits the bottleneck link it gets re-routed through alternative uncongested paths. If alternative paths do not exist, incoming content is temporarily stored in in-network caches, while the system enters a closed-loop, back-pressure mode of operation to avoid congestive collapse. Our proposal follows in spirit the resource pooling principle, which, however, is restricted to end-to-end resources and paths. We extend this principle to also take advantage of in-network resources, in terms of multiplicity of available sub-paths (as compared to multihomed users only) and in-network cache space. We call the proposed principle In-Network Resource Pooling Principle (INRPP). Using the INRPP, congestion, or increased contention over a link, is dealt with locally in a hop-by-hop manner, instead of end-to-end. INRPP utilises resources throughout the network more efficiently and opens up new directions for research in the multipath routing and congestion control areas

Hash-routing schemes for information centric networking.

It is our great pleasure to welcome you to The 3rd ACM SIGCOMM Workshop on Information-Centric Networking (ICN 2013). The fundamental concept in Information-Centric Networking (ICN) is to evolve the Internet from today's host based packet delivery towards directly retrieving information objects by names in a secure, reliable, scalable, and efficient way. These architectural design efforts aim to directly address the challenges that arise from the increasing demands for highly scalable content distribution, from accelerated growths of mobile devices, from wide deployment of the Internet-of-Things (IoT), and from the need to secure the global Internet. Rapid progress has been made over the last few years, initial designs are sketched, new research challenges exposed, and prototype implementations are deployed on testbeds of various scales. The research efforts have reached a new stage that allows one to experiment with proposed architectures and to apply a proposed architectural design to address real world problems. It also becomes important to compare different design approaches and develop methodologies for architecture evaluations. Some research areas, such as routing and caching, have drawn considerable attention; some other areas, such as trust management, effective and efficient application of cryptography, experience from prototyping, and lessons from experimentations, to name a few, have yet to be fully explored. This workshop presents original contributions on Information-Centric Networking architecture topics, specific algorithms and protocols, as well as results from implementations and bexperimentation, with an emphasis on applying the new approach to address real world problems and on experimental investigations. New for this year is that the workshop includes a poster/demo session. We received a large number of submissions and as the workshop is limited in time we were only able to accept 20% of them as full papers. To promote sharing of latest results among workshop attendees, we also accepted 17% of the submissions as posters or demos