National Centre of Scientific Research "Demokritos"

About: National Centre of Scientific Research "Demokritos" is a facility organization based out in Athens, Greece. It is known for research contribution in the topics: Computer science & Aerosol. The organization has 471 authors who have published 640 publications receiving 14478 citations. The organization is also known as: Demokritos.

A low-background Micromegas detector for axion searches

Abstract: A micropattern low-background detector based on the Micromegas technology has been designed and constructed for the CERN Axion Search experiment CAST. The detector is made of low natural radioactivity materials and has a two-dimensional readout with X–Y strip structure. It is operated with an Argon/Isobutane (95%/5%) mixture and is controlled by a VME data acquisition system. The detector is sensitive to photons in the energy range of 1–10 keV, it has a linear response, excellent stability and a very good energy resolution (14% FWHM at 5.9 keV). This device has been in stable operation since October 2002, taking data during the running periods of the CAST experiment. At the end of summer 2003, the detector was upgraded with a flash ADC readout of the grid signal to further improve its background rejection capability. The currently achieved background rate under normal operation is about 2.0 � 10 � 5 events/keV/cm 2 /s with better than 85% software efficiency.

Effect of the Standard Nomenclature for Air Pollution (SNAP) Categories on Air Quality over Europe

Abstract: The contribution of different anthropogenic source-sectors on ozone mixing ratios and PM2.5 concentrations over Europe is assessed for a summer month (July 2006) using the US Environmental Protection Agency’s (EPA’s) Models-3 framework and the Netherlands Organization for Applied Scientific Research (TNO) anthropogenic emissions for 2006. Anthropogenic emission sources have been classified into 10 different Standard Nomenclature for Air Pollution (SNAP) categories. The road transport category, which is mainly responsible for NOX emissions, is estimated to have the major impact on Max8hrO3 mixing ratio suggesting an increase of 6.8% on average over Europe, while locally it is more than 20%. Power generation category is estimated to have the major impact on PM2.5 concentrations since it is the major source of SO2 emissions, suggesting an increase of 22.9% on average over Europe, while locally it is more than 60%. Agriculture category is also contributing significantly on PM2.5 concentrations, since agricultural activities are the major source of NH3 emissions, suggesting an increased by 16.1% on average over Europe, while in regions with elevated NH3 emissions the increase is up to 40%.

Time Series Forecasting of Hourly PM10 Using Localized Linear Models

Abstract: The present paper discusses the application of localized linear models for the prediction of hourly PM10 concentration values. The advantages of the proposed approach lies in the clustering of the data based on a common property and the utilization of the target variable during this process, which enables the development of more coherent models. Two alternative localized linear modelling approaches are developed and compared against benchmark models, one in which data are clustered based on their spatial proximity on the embedding space and one novel approach in which grouped data are described by the same linear model. Since the target variable is unknown during the prediction stage, a complimentary pattern recognition approach is developed to account for this lack of information. The application of the developed approach on several PM10 data sets from the Greater Athens Area, Helsinki and London monitoring networks returned a significant reduction of the prediction error under all examined metrics against conventional forecasting schemes such as the linear regression and the neural networks.

Consequence analysis of an open fire incident in a pesticide storage plant

Abstract: This paper deals with the consequence assessment of an open fire incident in a Pesticides Storage Facility. Consequences are mainly caused by the atmospheric dispersion of toxic substances produced during the fire and transported downwind to considerable distance. An integrated methodology, based on Computational fluid Dynamics (CFD) techniques and the dimensionless buoyancy flux number, F / U 3 L , a parameter that can be associated with the flow characteristics, taking advantage of the dynamic similarity of the flow domain, is presented and used for the simulation of the plume dispersion. Rise to the present study gave a real incident, which happened in northern Greece in the beginning of 2004 and constituted the basis for the development of the accident scenarios eventually studied. Owing to the uncertainty in the estimation of source term strength and specifically of the magnitude of the heat released during the incident together with the variation in wind velocity, a parameterization of these two quantities has been applied. Four typical accident scenarios have been designed and studied. It is concluded that the proposed methodology allows for the calculation of the ground level concentration of any non-reactive substance dispersed in the atmosphere and constitutes a complementary approach in the consequence analysis of accidents in agrochemical (pesticides) plants.

Digital Enhancement of Cultural Experience and Accessibility for the Visually Impaired

Abstract: Visual impairment restricts everyday mobility and limits the accessibility of places, which for the non-visually impaired is taken for granted. A short walk to a close destination, such as a market or a school becomes an everyday challenge. In this chapter, we present a novel solution to this problem that can evolve into an everyday visual aid for people with limited sight or total blindness. The proposed solution is a digital system, wearable like smart-glasses, equipped with cameras. An intelligent system module, incorporating efficient deep learning and uncertainty-aware decision-making algorithms, interprets the video scenes, translates them into speech, and describes them to the user through audio. The user can almost naturally interact with the system via a speech-based user interface, which is also capable of understanding the user’s emotions. The capabilities of this system are investigated in the context of accessibility and guidance to outdoor environments of cultural interest, such as the historic triangle of Athens. A survey of relevant state-of-the-art systems, technologies and services is performed, identifying critical system components that better adapt to the goals of the system, user needs and requirements, toward a user-centered architecture design.