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Search Results: 1 - 10 of 190560 matches for " Panagiotis G. Demertzis "
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Determination of Five (5) Possible Contaminants in Recycled Cardboard Packages and Food Simulants Using Ultrasound Assisted Extraction Coupled to GC-MS  [PDF]
Ioanna-Efpraxia Parigoridi, Konstantoula Akrida-Demertzi, Panagiotis G. Demertzis
Materials Sciences and Applications (MSA) , 2014, DOI: 10.4236/msa.2014.510075
Abstract:
A modified analytical procedure has been developed to test for 5 organic pollutants [benzophenone, 2 diisopropylnaphthalenes (DIPNs) {2,6- and 2,7-diisopropylnapthalene} and 2 hydrogenated terphenyls (HTPs) {m-terphenyl and o-terphenyl}] that can be found as residues in recycled cardboards intended for use as food packaging materials and to test for migration levels of these compounds in a food simulant (Tenax). A main objective was to develop a modified rapid and reliable method for the identification and quantification of these compounds at low concentrations. The method was based on ultrasound-assisted solvent extraction (UAE) followed by gas chromatography-mass spectrometry (GC-MS) analysis. The developed method was applied to analyze 3 commercially available recycled carton board food-packaging materials and also to study the potential migration of the 5 organic pollutants from these materials into Tenax to check if these recycled cardboards can be considered as suitable for use in direct contact with foodstuffs. The limits of detection (LODs) of standard solutions of the 5 compounds were determined at a signal-to-noise ratio of 3. The LODs and the limits of quantification (LOQs) of examined pollutants ranged between 0.005 to 0.5 mg/kg, and 0.1 to 1 mg/kg, respectively. The extremely low amounts of most contaminants that migrate from packaging materials to Tenax indicate that the recycled cardboards tested can be safely used for direct food contact applications.
“Matters of Life and Death” in a Mediterranean Port City: Infrastructure, Housing and Infectious Disease in Patras, 1901–1940
Panagiotis G. Eliopoulos
Hygiea Internationalis : an Interdisciplinary Journal for the History of Public Health , 2010,
Abstract: For the first four decades of the 20th century, infectious diseases were the main cause for the high mortality Greek cities witnessed in their rather late urbanization period. Urban sprawl, combined with the absence of consistent urban planning policies led to a deterioration of living conditions and sanitation, which was ultimately translated in excessive infectious disease related deaths. Patras being a major port-city was heavily struck by a number of infectious diseases (many of which had become endemic to the city) although deaths were not distributed evenly among its population, showing instead a strong relation between income and health.It was only after the arrival of the Asia Minor/Pontus refugees (1922) and the frequent epidemic outbreaks that followed when both central government and municipal authorities would initiate many sanitation schemes that would help in the prevention of large scale epidemics in the 1930’s.
Dynamic Conditional Correlation between Electricity, Energy (Commodity) and Financial Markets during the Financial Crisis in Greece  [PDF]
Panagiotis G. Papaioannou, George P. Papaioannou, Akylas Stratigakos, Christos Dikaiakos
Journal of Mathematical Finance (JMF) , 2017, DOI: 10.4236/jmf.2017.74055
Abstract: Liberalization of electricity markets has increasingly created the need for understanding the volatility and correlation structure between electricity, financial and energy commodity markets. This work reveals the existence of structural changes in correlation patterns among these markets and links the changes to both fundamentals and regulatory conditions prevailing in the markets, as well as the current European financial crisis. We apply a Dynamic Conditional Correlation (DCC) GARCH model to a set of market’s fundamental variables, related commodity markets and Greece’s financial market and microeconomic indexes to study their interaction. Emphasis is given on the period of severe financial crisis of the Country to understand “contagion” and volatility spillover between these markets. This approach enables us to capture the changing co-movement of assets within and between markets (financial, commodity, electricity) as market conditions change. The main results are that there is strong evidence of volatility spillover (or co-volatility) between financial and commodity market, while the Greek electricity market seems to be almost “isolated” from these two markets.
Capacity Performance of Adaptive Receive Antenna Subarray Formation for MIMO Systems
Theofilakos Panagiotis,Kanatas Athanasios G
EURASIP Journal on Wireless Communications and Networking , 2007,
Abstract: Antenna subarray formation is a novel RF preprocessing technique that reduces the hardware complexity of MIMO systems while alleviating the performance degradations of conventional antenna selection schemes. With this method, each RF chain is not allocated to a single antenna element, but instead to the complex-weighted and combined response of a subarray of elements. In this paper, we derive tight upper bounds on the ergodic capacity of the proposed technique for Rayleigh i.i.d. channels. Furthermore, we study the capacity performance of an analytical algorithm based on a Frobenius norm criterion when applied to both Rayleigh i.i.d. and measured MIMO channels.
Capacity Performance of Adaptive Receive Antenna Subarray Formation for MIMO Systems
Panagiotis Theofilakos,Athanasios G. Kanatas
EURASIP Journal on Wireless Communications and Networking , 2007, DOI: 10.1155/2007/56471
Abstract: Antenna subarray formation is a novel RF preprocessing technique that reduces the hardware complexity of MIMO systems while alleviating the performance degradations of conventional antenna selection schemes. With this method, each RF chain is not allocated to a single antenna element, but instead to the complex-weighted and combined response of a subarray of elements. In this paper, we derive tight upper bounds on the ergodic capacity of the proposed technique for Rayleigh i.i.d. channels. Furthermore, we study the capacity performance of an analytical algorithm based on a Frobenius norm criterion when applied to both Rayleigh i.i.d. and measured MIMO channels.
Quizz: Targeted crowdsourcing with a billion (potential) users
Panagiotis G. Ipeirotis,Evgeniy Gabrilovich
Computer Science , 2015, DOI: 10.1145/2566486.2567988
Abstract: We describe Quizz, a gamified crowdsourcing system that simultaneously assesses the knowledge of users and acquires new knowledge from them. Quizz operates by asking users to complete short quizzes on specific topics; as a user answers the quiz questions, Quizz estimates the user's competence. To acquire new knowledge, Quizz also incorporates questions for which we do not have a known answer; the answers given by competent users provide useful signals for selecting the correct answers for these questions. Quizz actively tries to identify knowledgeable users on the Internet by running advertising campaigns, effectively leveraging the targeting capabilities of existing, publicly available, ad placement services. Quizz quantifies the contributions of the users using information theory and sends feedback to the advertisingsystem about each user. The feedback allows the ad targeting mechanism to further optimize ad placement. Our experiments, which involve over ten thousand users, confirm that we can crowdsource knowledge curation for niche and specialized topics, as the advertising network can automatically identify users with the desired expertise and interest in the given topic. We present controlled experiments that examine the effect of various incentive mechanisms, highlighting the need for having short-term rewards as goals, which incentivize the users to contribute. Finally, our cost-quality analysis indicates that the cost of our approach is below that of hiring workers through paid-crowdsourcing platforms, while offering the additional advantage of giving access to billions of potential users all over the planet, and being able to reach users with specialized expertise that is not typically available through existing labor marketplaces.
Financially Stimulating Local Economies by Exploiting Communities’ Microgrids: Power Trading and Hybrid Techno-Economic (HTE) Model
Athanasios G. Lazaropoulos, Panagiotis Lazaropoulos
Trends in Renewable Energy , 2015, DOI: 10.17737/tre.2015.1.3.0014
Abstract: This paper thoroughly considers the potential of installing microgrids (MGs) in communities that suffer from the economic crisis in order to financially stimulate their local economies. Exploiting the state-of-the-art evolutions in the fields of the MG technology, the Hybrid Techno-Economic (HTE) model is proposed as a suitable techno-economic tool for assessing the power generation/consumption behaviour and the financial performance of these communities’ MGs. The contribution of this paper is four-fold. First, the HTE model is presented. HTE model describes a theoretical analysis that is suitable for studying community’s MGs. Appropriately concatenating one well-validated technical module and one new economic module, the HTE model quickly and conveniently reveals the power generation/consumption and economic profile of community’s MGs. Second, HTE model is integrated through an extended portfolio of power and financial metrics. The applied metrics study the influence of generation and consumption power changes on community’s MGs. The validity and the efficiency of the HTE model are examined with respect to these power changes while the impact of these changes on the power and cash flows of community’s MGs are assessed. Third, a cost-benefit analysis of the operation of community’s MGs accompanied with a financial stability analysis is also demonstrated. The main outcome of these analyses is the daily total benefit (TB) of community’s MGs with its respective financial bounds. Fourth, the contribution of the energy arbitrage and the power production mix among available power sources of community’s MGs to the daily TB is investigated. Apart from promoting the ecological awareness, this paper tries to become a catching argument for the communities in order to exploit the community’s MGs.
Cultivation and Characterization of Cynara Cardunculus for Solid Biofuels Production in the Mediterranean Region
Panagiotis Grammelis,Anastasia Malliopoulou,Panagiotis Basinas,Nicholas G. Danalatos
International Journal of Molecular Sciences , 2008, DOI: 10.3390/ijms9071241
Abstract: Technical specifications of solid biofuels are continuously improved towards the development and promotion of their market. Efforts in the Greek market are limited, mainly due to the climate particularity of the region, which hinders the growth of suitable biofuels. Taking also into account the increased oil prices and the high inputs required to grow most annual crops in Greece, cardoon (Cynara cardunculus L.) is now considered the most important and promising sources for solid biofuel production in Greece in the immediate future. The reason is that cardoon is a perennial crop of Mediterranean origin, well adapted to the xerothermic conditions of southern Europe, which can be utilized particularly for solid biofuel production. This is due to its minimum production cost, as this perennial weed may perform high biomass productivity on most soils with modest or without any inputs of irrigation and agrochemicals. Within this framework, the present research work is focused on the planning and analysis of different land use scenarios involving this specific energy crop and the combustion behaviour characterization for the solid products. Such land use scenarios are based on quantitative estimates of the crop’s production potential under specific soil-climatic conditions as well as the inputs required for its realization in comparison to existing conventional crops. Concerning its decomposition behaviour, devolatilisation and char combustion tests were performed in a non-isothermal thermogravimetric analyser (TA Q600). A kinetic analysis was applied and accrued results were compared with data already available for other lignocellulosic materials. The thermogravimetric analysis showed that the decomposition process of cardoon follows the degradation of other lignocellulosic fuels, meeting high burnout rates. This research work concludes that Cynara cardunculus, under certain circumstances, can be used as a solid biofuel of acceptable quality.
Cultivation and Characterization of Cynara Cardunculus for Solid Biofuels Production in the Mediterranean Region
Panagiotis Grammelis,Anastasia Malliopoulou,Panagiotis Basinas,Nicholas G. Danalatos
International Journal of Molecular Sciences , 2008,
Abstract: Technical specifications of solid biofuels are continuously improved towards the development and promotion of their market. Efforts in the Greek market are limited, mainly due to the climate particularity of the region, which hinders the growth of suitable biofuels. Taking also into account the increased oil prices and the high inputs required to grow most annual crops in Greece, cardoon (Cynara cardunculus L.) is now considered the most important and promising sources for solid biofuel production in Greece in the immediate future. The reason is that cardoon is a perennial crop of Mediterranean origin, well adapted to the xerothermic conditions of southern Europe, which can be utilized particularly for solid biofuel production. This is due to its minimum production cost, as this perennial weed may perform high biomass productivity on most soils with modest or without any inputs of irrigation and agrochemicals. Within this framework, the present research work is focused on the planning and analysis of different land use scenarios involving this specific energy crop and the combustion behaviour characterization for the solid products. Such land use scenarios are based on quantitative estimates of the crop ¢ € s production potential under specific soil-climatic conditions as well as the inputs required for its realization in comparison to existing conventional crops. Concerning its decomposition behaviour, devolatilisation and char combustion tests were performed in a non-isothermal thermogravimetric analyser (TA Q600). A kinetic analysis was applied and accrued results were compared with data already available for other lignocellulosic materials. The thermogravimetric analysis showed that the decomposition process of cardoon follows the degradation of other lignocellulosic fuels, meeting high burnout rates. This research work concludes that Cynara cardunculus, under certain circumstances, can be used as a solid biofuel of acceptable quality.
Cubic-Quintic Long-Range Interactions With Double Well Potentials
Panagiotis A. Tsilifis,Panagiotis G. Kevrekidis,Vassilios M. Rothos
Physics , 2012,
Abstract: In the present work, we examine the combined effects of cubic and quintic terms of the long range type in the dynamics of a double well potential. Employing a two-mode approximation, we systematically develop two cubic-quintic ordinary differential equations and assess the contributions of the long-range interactions in each of the relevant prefactors, gauging how to simplify the ensuing dynamical system. Finally, we obtain a reduced canonical description for the conjugate variables of relative population imbalance and relative phase between the two wells and proceed to a dynamical systems analysis of the resulting pair of ordinary differential equations. While in the case of cubic and quintic interactions of the same kind (e.g. both attractive or both repulsive), only a symmetry breaking bifurcation can be identified, a remarkable effect that emerges e.g. in the setting of repulsive cubic but attractive quintic interactions is a "symmetry restoring" bifurcation. Namely, in addition to the supercritical pitchfork that leads to a spontaneous symmetry breaking of the anti-symmetric state, there is a subcritical pitchfork that eventually reunites the asymmetric daughter branch with the anti-symmetric parent one. The relevant bifurcations, the stability of the branches and their dynamical implications are examined both in the reduced (ODE) and in the full (PDE) setting.
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