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Search Results: 1 - 10 of 88331 matches for " Alexandros I. Nikolaidis "
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Indices to Assess the Integration of Renewable Energy Resources on Transmission Systems
Alexandros I. Nikolaidis,Francisco M. Gonzalez-Longatt,C. A. Charalambous
Conference Papers in Science , 2013, DOI: 10.1155/2013/324562
Abstract: The continuous increase on the penetration levels of Renewable Energy Sources (RESs) in power systems has led to radical changes on the design, operation, and control of the electrical network. This paper investigates the influence of these changes on the operation of a transmission network by developing a set of indices, spanning from power losses to GHG emissions reduction. These indices are attempting to quantify any impacts therefore providing a tool for assessing the RES penetration in transmission networks, mainly for isolated systems. These individual indices are assigned an analogous weight and are mingled to provide a single multiobjective index that performs a final evaluation. These indices are used to evaluate the impact of the integration of RES into the classic WSCC 3-machine, 9-bus transmission network. 1. Introduction European Union countries have a set of specific targets to promote the use of energy from Renewable Energy Source (RES) in accordance with the Directive 2009/28/EC of the European Parliament [1]. These National Action Plans (NAPs) consider and set targets for the final use of energy for heating and cooling, electricity generation, and transportation. In particular, electricity generation is of great interest as it requires the liberalization of the electricity markets. The 16% of global final energy consumption comes from renewable sources during 2012, with 10% coming from traditional biomass, which is mainly used for heating and 3.4% from hydroelectricity. New renewable sources (small hydro, modern biomass, wind, solar, geothermal, and biofuels) accounted for another 2.8% and are growing very rapidly [2]. The share of renewable sources in electricity generation is around 19%, with 16% of global electricity coming from hydroelectricity and 3% from new renewable sources [2]. Nevertheless, RESs have not been a significant part of the energy mix for the vast majority of countries around the world, fact which has led governments to provide incentives to entities that are interested in investing in RES electricity generation, in most cases using wind and solar power. Consequently, it is of crucial importance to investigate how RES generation affects the network’s operational ability and which potential configurations could prove beneficial. Hence, a series of technical aspects must be considered by the planners in order to evaluate the pros and cons of such penetration. In particular, the minimization of power losses has so far been the most important issue for the planners [3, 4]. However, other grid related technical aspects
A Variation of the Box-Counting Algorithm Applied to Colour Images
N. S. Nikolaidis,I. N. Nikolaidis,C. C. Tsouros
Computer Science , 2011,
Abstract: The box counting method for fractal dimension estimation had not been applied to large or colour images thus far due to the processing time required. In this letter we present a fast, easy to implement and very easily expandable to any number of dimensions variation, the box merging method. It is applied here in RGB images which are considered as sets in 5-D space.
Purification of Agro Waste Saffron Using Membrane Technology-Ultrafiltration-Application to Sunscreen Cosmetic Emulsions  [PDF]
Maria Zarkogianni, Nikolaos Nikolaidis
Open Journal of Applied Sciences (OJAppS) , 2016, DOI: 10.4236/ojapps.2016.67046
Abstract: In this present work, ultrafiltration was applied for the purification of agro waste Greek red saffron. The agro waste saffron (before and after ultrafiltration) was used for the preparation of oil- in-water emulsions. Produced emulsions were examined for their viscosity, pH and conductivity during time. Also surface tension values of the aqueous and oily phase of the emulsions were measured. Saffron is known for its antioxidant and anti-solar properties. Anti-solar activity of saffron was evaluated by measuring the SPF value of the emulsion. UV-Vis measurements have shown an incredible increase of the absorption of saffron after ultrafiltration. The emulsions made with the purified saffron presented a better anti-solar activity and at the same time remarkably improvement of their antioxidant and antiaging properties giving a very promising alternative to the cosmetic industry.
Vancomycin-resistant enterococci, colonizing the intestinal tract of patients in a university hospital in greece
Metallidis, Simeon;Chatzidimitriou, Maria;Tsona, Afroditi;Bisiklis, Alexandros;Lazaraki, Georgia;Koumentaki, Eleni;Gikas, Ahilleas;Alexiou-Daniel, Stela;Nikolaidis, Pavlos;
Brazilian Journal of Infectious Diseases , 2006, DOI: 10.1590/S1413-86702006000300005
Abstract: objective: determine the prevalence of vancomycin-resistant enterococci (vre) colonizing the intestinal tract of hospitalized patients and define risk factors. material and methods: a point prevalence survey of vre fecal carriage was carried out among patients who stayed at a 600-bed teaching hospital for at least two days. resistance to vancomycin was detected by the e-test method. epidemiological data was recorded for all patients included in the study and was used for the risk factor analysis. results: a total of 128 patients hospitalized for at least two days were enrolled in this investigation. thirty-nine patients (30.5%) were colonized with vancomycin-resistant enterococci. twenty-three of the 39 strains were identified as enterococcus faecium, 13 were identified as enterococcus gallinarum and three strains as enterococcus casseliflavus. the risk factors that were significantly associated with vre colonization included length of hospital stay (13.2 days vs. 8.6 days), age (60.7 years vs. 47.7 years) and the presence of underlying malignancies (28.2% vs. 11.2%). an association was found between vre colonization and the use of antimicrobials with anaerobic activity, such as metronidazole, piperacillin/tazobactam and imipenem. the use of vancomycin was associated with vre colonization in the intensive care unit. conclusions: vre colonization must be monitored, and risk factors should be determined, because they are useful for screening hospitalized patients for vre colonization in order to establish prevention and control measures.
The hygieinic importance of water quality in renal dialysis units
Costantinidis T. G.,Nikolaidis C.,Alexandropoulou I.,Costantinidis T. K.
Interscientific Health Care , 2011,
Abstract: The microbiological and chemical quality of water used in haemodialysis units must comply with several hygienic conditions that do not compromise the nephropathic patient’s health. Every week patients undergoing renal therapy are exposed to approximately 400 liters of water that are used to manufacture haemodialysis liquids. Efficient monitoring of water quality in Renal Dialysis Units (RDU) can address the microbiological and chemical hazards and prevent complications associated with the impurity of hemodialysis liquids (e.g. inflammatory, infectious and toxicological reactions). This review article aims at elucidating the importance of water quality in RDU, describe the methods used for quality assurance and promote the active role of the laboratory in preventing these hazards through efficient monitoring.
GENDER DIFFERENCES IN ANAEROBIC POWER IN PHYSICAL EDUCATION AND SPORT SCIENCE STUDENTS
Pantelis Nikolaidis
Citius Altius Fortius , 2009,
Abstract: Purpose: To find out gender differences in anaerobic power and capacity in Physical Education and Sportstudents. Methods: 56 female (age 22.72 years old ± 1.96, body mass 60.7 Kg ± 6.06, stature 1.69 m ± 0.06 andbody mass index 21.19 Kg.m-2 ± 1.92, mean ± standard deviation) and 152 male students (23.34 years old ± 2.14,77.3 Kg ± 7.85, 1.82 m ± 0.06 and 23.28 ± 1.93 Kg.m-2) realized the Wingate anaerobic test. Results: The maleshowed significantly higher values in the main indexes of the test, peak power-PP (63.36 % in absolute and28.03 % in relative to body mass values), mean power-MP (60.76 % in absolute and 26.06 % in relative to bodymass values) and fatigue index (8.15 %) with comparison to female students. Female and male students revealedsimilar and high correlation between body mass and power parameters in absolute values (r=0.79 and r=0.81 forPP and 0.79 and 0.82 for MP, correspondingly). Conclusion: The significant gender differences in anaerobicpower support the teaching in separate classes according to gender and it is suggested to consider thesequantitative differences in the design of effective study programs. Key Words: Wingate, ergometry, studyprograms.
The Nature of Economic Turbulence: The Power Destructing Economies, with Application to Shipping  [PDF]
Alexandros M. Goulielmos, Alexandros M. Goulielmos
Modern Economy (ME) , 2018, DOI: 10.4236/me.2018.95066
Abstract: Studying the history of “economic turbulence”, we ended up with the certainty that the statistical methods used so far, by economists, are unsuitable to model it. We have mainly the methods of Normal distribution and Random Walk in mind. Moreover, the picture of reality we get from time series depends on the time-frame of the data used… Different time-frame data, different reality… In addition, econometricians provided a whole family of econometric models to approach reality, starting in early 1980s, with “autoregressive models—AR” combined or not with MA (moving averages). But even its 1986 flagship, the GARCH, with its many variations, cannot cope with a number of characteristics, one of which is leptokurtosis (small alpha, higher peaks and long tails), though some argue that it can cater for outliers. Economic turbulence, low or high—despite its characterization by Science as rare—became frequent since 1987 (Black Monday)... In late 1990s e.g. the global financial system underwent 6 crises—which have been called “near turbulences”—over a number of countries, including Russia in 1998. The next turbulence will not be one generation apart—we reckon. This paper is an attempt to invite writers to write a “theory of economic turbulence”. Turbulence is a nightmare, which wakes people up suddenly, and unexpectedly, but it is something people wish to forget… till it strikes again: turbulence stroke in 1929 on (Black) Tuesday, then in 1987 on (Black) Monday and in end-2008, the Great Recession—on 29th September. In Black Monday stock markets around the world crashed losing a huge value in a matter of very short time (Hong Kong, Europe, and USA). The Dow fell ~23%. At that time OPEC collapsed in 1986 and the price of oil doubled… The dry cargo shipping sector entered a turbulent situation since 1989, which has been deteriorated since 2015 reaching finally an alpha equal to ~1.43 < 1.70 by 2035…
Polarizability Matrix Extraction of a Bianisotropic Metamaterial from the Scattering Parameters of Normally Incident Plane Waves
Theodosios D. Karamanos,Alexandros I. Dimitriadis,Kantartzis Nikolaos V.
Advanced Electromagnetics , 2012, DOI: 10.7716/aem.v1i3.73
Abstract: In this paper, a polarizability matrix retrieval method for bianisotropic metamaterials is presented. Assuming that scatterers can be modeled by electric and magnetic pointdipoles located at their centers, the induced dipole moments are analytically related to the normally incident fields, while the scattered fields are also analytically obtained for two individual cases of normal wave incidence. The latter can be combined with the incident fields, to express the desired polarizabilities, with regard to the measured or simulated scattering parameters. In this way, the polarizability matrix can be extracted by solving the resulting non-linear system of equations. The proposed technique is applied to two different split-ring resonator structures and reveals very good agreement with previously reported techniques.
Combined FVTD/PSTD Schemes with Enhanced Spectral Accuracy for the Design of Large-Scale EMC Applications
Nikolaos V Kantartzis,Alexandros I Dimitriadis,Theodoros D Tsiboukis
Advanced Electromagnetics , 2012, DOI: 10.7716/aem.v1i3.46
Abstract: A generalized conformal time-domain method with adjustable spectral accuracy is introduced in this paper for the consistent analysis of large-scale electromagnetic compatibility problems. The novel 3-D hybrid schemes blend a stencil-optimized finite-volume time-domain and a multimodal Fourier-Chebyshev pseudo-spectral time-domain algorithm that split the overall space into smaller and flexible areas. A key asset is that both techniques are updated independently and interconnected by robust boundary conditions. Also, combining a family of spatial derivative approximators with controllable precision in general curvilinear coordinates, the proposed method launches a conformal field flux formulation to derive electromagnetic quantities in regions with fine details. For advanced grid reliability at dissimilar media interfaces, dispersion-reduced adaptive operators, which assign the proper weights to each spatial increment, are developed. So, the resulting discretization yields highly rigorous and computationally affordable simulations, devoid of lattice errors. Numerical results, addressing detailed comparisons of various realistic applications with reference or measurement data verify our methodology and reveal its significant applicability.
Influence of magnetic interaction between impurity and impurity-liberated spins on the magnetism in the doped Haldane chain compounds PbNi${}_{2-x${A}${}_{x}$V${}_{2}$O${}_{8}$ (A = Mg, Co)
Andrej Zorko,Denis Ar?on,Alexandros Lappas,Zvonko Jagli?i
Physics , 2005, DOI: 10.1103/PhysRevB.73.104436
Abstract: A comprehensive study of impurity-induced magnetism in nonmagnetically (Mg${}^{2+}$) and magnetically (Co${}^{2+}$) doped PbNi${}_{2}$V${}_{2}$O${}_{8}$ compounds is given, using both macroscopic dc susceptibility and local-probe electron spin resonance (ESR) techniques. Magnetic coupling between impurity-liberated spins is estimated from a linewidth of low-temperature ESR signal in Mg-doped samples. In addition, in the case of magnetic cobalt dopants the impurity-host magnetic exchange is evaluated from the Co-induced contribution to the linewidth in the paramagnetic phase. The experimentally observed severe broadening of the ESR lines in the magnetically doped compounds with respect to nonmagnetic doping is attributed to a rapid spin-lattice relaxation of the Co${}^{2+}$ ions, which results in a bottleneck-type of temperature dependence of the induced linewidth. The exchange parameters obtained from the ESR analysis offer a satisfactory explanation of the observed low-temperature magnetization in doped samples.
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