Electrical Engineering and Computer Science

In this paper, the generation scheduling problem for autonomous island systems with significant penetration of non-dispatchable Renewable Energy Source (RES) generation is investigated, proposing a unit commitment-economic dispatch (UC-ED) model which is fully compatible with the provisions of the regulatory framework currently applicable to the Greek non-interconnected island (NII) systems. Two UC-ED model variants are presented and comparatively assessed, in order to illustrate the impact of various system parameters (technical characteristics of the thermal units, reserve requirements, etc.) on the expected operating profile of the NII system. A detailed UC-ED model is first proposed, which takes into account the reserve requirements at different time scales (primary, secondary and tertiary reserves) and respective capabilities of generating units. An alternative, simplified UC-ED model is also presented, formulated on the basis of aggregate spinning reserves, to cater for uncertainties in the actual reserve capabilities of existing thermal units. The developed UC-ED models are applied to an existing NII system to evaluate their performance and results obtained on an annual basis.

Detection of perceptually important video events is formulated here on the basis of saliency models for the audio, visual and textual information conveyed in a video stream. Audio saliency is assessed by cues that quantify multifrequency waveform modulations, extracted through nonlinear operators and energy tracking. Visual saliency is measured through a spatiotemporal attention model driven by intensity, color and motion. Text saliency is extracted from part-of-speech tagging on the subtitles information available with most movie distributions. The various modality curves are integrated in a single attention curve, where the presence of an event may be signi ed in one or multiple domains. This multimodal saliency curve is the basis of a bottom-up video summarization algorithm, that re nes results from unimodal or audiovisual-based skimming. The algorithm performs favorably for video summarization in terms of informativeness and enjoyability.

Based on perceptual and computational attention modeling studies, we formulate measures of saliency for an audiovisual stream. Audio saliency is captured by signal modulations and related multifrequency band features, extracted through nonlinear operators and energy tracking. Visual saliency is measured by means of a spatiotemporal attention model driven by various feature cues (intensity, color, motion). Audio and video curves are integrated in a single attention curve, where events may be enhanced, suppressed or vanished. The presence of salient events is signified on this audiovisual curve by geometrical features such as local extrema, sharp transition points and level sets. An audiovisual saliency-based movie summarization algorithm is proposed and evaluated. The algorithm is shown to perform very well in terms of summary informativeness and enjoyability for movie clips of various genres.

Nowadays, the proliferation of cloud-based services (CBS) has revolutionized the way people communicate, connect, share and eventually conduct business. Large and small and medium enterprises often adapt to this era by providing their core competence through an API. The present paper aims at describing a solution that manages, advances and unifies the functionality of the various CBS under a common framework that is being developed as a coherent graph API. Since the task of handling the evolution and complexity of the CBS API lifecycle is high, the framework is accompanied by a tool that creates a community of enterprises and developers actively engaged both in the usage of the Generic Graph APIs, but also in the update and improvement of these initial APIs.

Creating added value, innovative applications and services in the web is hindered by the prevailing different formats and models of information retrieved by the various Cloud-based Services (CBS). Additionally, CBS tend to change their Application Programming Interface (API) versions very often, not sufficiently helping the interested enterprises with their adoption as they need to be up-to-date and always functional. The API Builder is a community based platform that aims to facilitate developers in adopting a Graph API that unifies the experience of multiple cloud-based services APIs and personal cloudlets, building and maintaining their software applications easily, despite any changes made in the CBS APIs.

Today’s mobile applications, spanning from file storage and syncing, place checking in and tagging, multimedia sharing, streaming and recommendation, to social and professional networking, rely a lot on cloud-based services, which in turn offer increasingly more functionalities through their publicly available APIs. Users have greeted this abundance of services with even greater demand for innovative applications to address personal and business needs, but are still unaware of the full power that could be leveraged from their data, currently scattered on various platforms. In this complex ecosystem of mobile applications OPENi offers a way to facilitate developers into building applications over the multiple and diverse APIs but also provides users with their own personal cloud storage space, the "Cloudlet", equipped with strong privacy controlling mechanisms, accessed through its open-source Graph API platform. New business models can thus be deployed that leverage the full potential of the available data and metadata, offering application developers the means to create powerful but also privacy-aware services, respecting the requirements of both parties, i.e. service providers and data-owners.

More and more users, these days, keep fragmented data across the web in different applications, through various types of devices, PC, mobiles, wearable devices, etc. By taking advantage of an aggregative Graph Application Programming Interface (API), users have the ability to harness shattered data and keep them into a privacy-aware platform (Cloudlet) where permissions can be applied, and therefore let developers build useful applications from it. To make this unifying Graph API, the API Builder is proposed, as a tool for easily creating new APIs and connecting them with existing ones from Cloud-based Services (CBS), thus providing integration among services and making it easier for users and/or enterprises to reach a larger audience while conveying their message. Typical obstacles, like keeping up to date with CBS API versioning, that seems daunting for developers, are also tackled through semi-automation and the help of the community empowering the API Builder. In that way, application developers do not have to worry for merging various APIs or if the application-generated data are locked in silos of companies; now the user is the judge who gives access to their data and meta-data (i.e. especially context), to enable smarter, context-adaptive and richer in content applications.