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Search Results: 1 - 10 of 276187 matches for " E. V. Liarakos "
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Nondestructive Wireless Monitoring of Early-Age Concrete Strength Gain Using an Innovative Electromechanical Impedance Sensing System
C. P. Providakis,E. V. Liarakos,E. Kampianakis
Smart Materials Research , 2013, DOI: 10.1155/2013/932568
Abstract: Monitoring the concrete early-age strength gain at any arbitrary time from a few minutes to a few hours after mixing is crucial for operations such as removal of frameworks, prestress, or cracking control. This paper presents the development and evaluation of a potential active wireless USB sensing tool that consists of a miniaturized electromechanical impedance measuring chip and a reusable piezoelectric transducer appropriately installed in a Teflon-based enclosure to monitor the concrete strength development at early ages and initial hydration states. In this study, the changes of the measured electromechanical impedance signatures as obtained by using the proposed sensing system during the whole early-age concrete hydration process are experimentally investigated. It is found that the proposed electromechanical impedance (EMI) sensing system associated with a properly defined statistical index which evaluates the rate of concrete strength development is very sensitive to the strength gain of concrete structures from their earliest stages. 1. Introduction Since accurate field measurements of early-age concrete properties, such as setting time, in-place strength gain, and shrinkage stresses, are crucial to in situ quality control of concrete, various techniques have been proposed including Windsor and pullout probe tests, ultrasonic pulse velocity, impact-echo method, microwave method, and maturity method [1]. Those nondestructive techniques interactively measure certain mechanical properties of the concrete from which information on the strength is derived. However, although mechanical wave velocity methods such as the ultrasonic pulse velocity and impact-echo methods are widely used to test in a nondestructive manner, they have some limitations that restrict practical applications. Thus, mainly due to their serious drawbacks they received little interest from the construction community. Besides, these methods use extensive wiring systems to operate and necessitate special equipment to gain access to the structure during construction. In addition, these techniques perform localized measurements, and the monitoring of large concrete structures requires an extensive amount of time and effort leading to costly usage. Substructures such as concrete foundations and piles are inaccessible and their early-age strength development cannot be evaluated using these monitoring systems. The advent of smart materials, such as piezoelectric materials, shape-memory alloys, and optical fibers, has attracted interests among researchers and engineers to develop new
Time-dependent alterations in serum NO concentration after oral administration of L-arginine, L-NAME, and allopurinol in intestinal ischemia/reperfusion
Amalia E Yanni,Eleutherios Margaritis,Nikolaos Liarakos,Alkisti Pantopoulou
Vascular Health and Risk Management , 2008,
Abstract: Amalia E Yanni1, Eleutherios Margaritis2, Nikolaos Liarakos2, Alkisti Pantopoulou2, Maria Poulakou2, Maria Kostakis2, Despoina Perrea2, Alkis Kostakis31Department of Science of Dietetics and Nutrition, Harokopio University of Athens, Athens, Greece, 2Laboratory of Experimental Surgery and Surgical Research, School of Medicine, National and Kapodistrian University of Athens, Athens, Greece, 32nd Department of Propedeutic Surgery, School of Medicine, National and Kapodistrian University of Athens, Athens, GreeceObjective: To study the effect of oral administration of a nitric oxide (NO) donor L-arginine (L-Arg), a NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) and an inhibitor of xanthine oxidase, allopurinol (Allo), on serum NO concentration and catalase activity after intestinal ischemia/reperfusion (I/R) in rats.Methods: Male Wistar rats received per os L-Arg (800 mg/kg) or L-NAME (50 mg/kg) or Allo (100 mg/kg) 24 hrs, 12 hrs and 1 hr before underwent 1 hr occlusion of superior mesenteric artery followed by 1 hr of reperfusion (L-Arg(IR1), L-NAME(IR1) and Allo(IR1) respectively) or 1 hr occlusion followed by 8 hrs of reperfusion (L-Arg(IR8), L-NAME(IR8) and Allo(IR8) respectively). There was one group underwent 1 hr occlusion (I), a group underwent 1 hr occlusion followed by 1 hr reperfusion (IR1), a group subjected to 1 hr occlusion followed by 8 hrs of reperfusion (IR8) and a last group that served as control (C). Serum NO concentration and catalase activity were measured.Results: After 1 hr of reperfusion serum NO concentration was elevated in IR1 and L-Arg(IR1) groups compared with group C but not in L-NAME(IR1) and Allo(IR1) group. Catalase activity was enhanced in L-NAME(IR1) group. Interestingly, serum NO concentration was increased after 8 hrs of reperfusion in all groups (IR8, L-Arg(IR8), L-NAME(IR8) and Allo(IR8)) compared with control while catalase activity did not show significant difference in any group.Conclusions: The results of the present study show that NO concentration is elevated in serum after intestinal I/R and the elevation sustained after administration of L-Arg but not after administration of L-NAME or Allo after 1 hr reperfusion. However, after 8 hrs of reperfusion NO concentration was increased in all groups studied, focusing attention on its possible important role in a complicated situation such as intestinal I/R that involves intestine and other organs. Serum catalase activity does not seem to be affected by per os supplementation of L-Arg or Allo in intestinal I/R.Keywords: intestine, ischemia-reperfusio
Methane Formation by the Reaction of Coalbed Carbon with Water  [PDF]
V. E. Vigdergauz
Geomaterials (GM) , 2011, DOI: 10.4236/gm.2011.11003
Abstract: There is proposed a mechanism of methane and carbon dioxide formation by the direct reaction of carbon with water during catastrophic events in the mining of coal deposits. Thermodynamics of the reaction is dis-cussed.
The Conservation of Energy Space-Time Metric for Space Outside Matter  [PDF]
V. N. E. Robinson
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.48149
Abstract:

By using experimentally determined measurements of potential energy together with the principle of conservation of energy and solving directly, the space-time geometry equation for space outside matter is obtained. That equation fits all the experimental observations that support the accepted Schwarzschild metric, yet predicts there isn’t a singularity at the Schwarzschild radius. The accepted Schwarzschild metric is the first approximation of the conservation of energy space-time metric. No observation yet made can distinguish between the predictions of the two metrics.

The Energy Conservation Paradox of Quantum Physics  [PDF]
V. E. Shapiro
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.611160
Abstract: This work asserts that quantum theory runs into a fundamental conflict with the principles of energy conservation inferred from the statistical evolution of interacting systems. The gist is the energy of systems by the principles of Lagrangian mechanics leaves out of account their energy associated with the phase flows of non-invariant phase volume. The quantum theory takes this fact into account, but does that improperly. We show it by presenting insoluble inconsistencies and a case study.
New Method of Thermal Energy—To Electrical Energy Conversion in Vacuum Devices with the Metal—Dielectric Nanofilm Electron Sources  [PDF]
V. E. Ptitsin
Materials Sciences and Applications (MSA) , 2018, DOI: 10.4236/msa.2018.913078
Abstract: New method of thermal energy—to electrical energy conversion in vacuum devices with the metal (W)—dielectric nanofilm (ZrO2) electron source is offered and studied. According to estimates and results of modeling, the energy effectiveness (χ) of the proposed method may exceed χ for the known thermionic energy conversion method to 2 - 3 orders of magnitude.
Peak Power Effect on Skin Rejuvenation Using IPL: Lumecca IPL Evaluation  [PDF]
E. V. Ross, Michael Kreindel
Advances in Aging Research (AAR) , 2016, DOI: 10.4236/aar.2016.53008
Abstract: A high peak power IPL system (Lumecca) was tested to determine the correlation between a high peak power and the successful treatment of pigmented and vascular lesions. Short pulse duration in the millisecond range and high peak power of 3.3 kW/cm2 enabled selective and effective destruction, not only of pigment, but also of vessels in a comparable manner to a pulsed dye laser. Only one treatment session at a low fluence (8 - 16 J/cm2) was sufficient to achieve the desired results.
Phonon Mediated Electron-Electron Scattering in Metals  [PDF]
V. Palenskis, E. ?itkevi?ius
World Journal of Condensed Matter Physics (WJCMP) , 2018, DOI: 10.4236/wjcmp.2018.83008
Abstract: It is shown that the linear resistivity dependence on temperature for metals above the Debye’s temperature mainly is caused by electron-electron scattering of randomly moving electrons. The electron mean free path in metals at this temperature range is in inverse proportion to the effective density of randomly moving electrons, i.e. it is in inverse proportion both to the temperature, and to the density-of-states at the Fermi surface. The general relationships for estimation of the average diffusion coefficient, the average velocity, mean free length and average relaxation time of randomly moving electrons at the Fermi surface at temperatures above the Debye’s temperature are presented. The effective electron scattering cross-sections for different metals also are estimated. The calculation results of resistivity dependence on temperature in the range of temperature from 1 K to 900 K for Au, Cu, Mo, and Al also are presented and compared with the experimental data. Additionally in temperature range from 1 K to 900 K for copper, the temperature dependences of the mean free path, average diffusion coefficient, average drift mobility, average Hall mobility, average relaxation time of randomly moving electrons, and their resultant phonon mediated scattering cross-section are presented.
Analysis of Rainfall Variability Using Remote Sensing and GIS in North Central Nigeria  [PDF]
O. Ideki, V. E. Weli
Atmospheric and Climate Sciences (ACS) , 2019, DOI: 10.4236/acs.2019.92013
Abstract: The importance of rainfall variability in successfully understanding the dynamics of climate change in any region cannot be overemphasized. This study examines rainfall variability in the North Central region including the Federal Capital Territory Abuja using remote sensing and geographic information system (GIS) application. The study employed satellite data basically from near real time data of Moderate Resolution Imaging Spectroradiometer (MODIS). Thereafter, the point data of rainfall was clipped to the shape file of Nigeria Boundary and interpolation using Inverse Distance Weight (IDW) was done to generate rainfall spatial maps from 2000-2017. The result reveal high temporal variation in rainfall particularly Niger, Plateau, Benue and Nassarawa states. The study therefore recommends close monitoring of periodic pattern of rainfall characteristics in the region by the Nigerian meteorological agency and to encourage farmers into drought tolerant and irrigation farming.
Numerical Modelling of Coal Combustion Processes in the Vortex Furnace with Dual-Port Loading  [PDF]
I. S. Anufriev, E. P. Kopyev, D. V. Krasinsky, V. V. Salomatov, E. Y. Shadrin, O. V. Sharypov
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B060
Abstract: The work is devoted to numerical simulation of pulverized-coal combustion processes in the vortex furnace which is a prospective design of a boiler unit for thermal power plants. New modification of this design characterized by additional tangential-injection nozzle located at the bottom of combustion chamber has been studied. Numerical results for the case of Siberian brown coal combustion in this vortex furnace with dual-port loading are presented, including 3-D aerodynamic structure, the fields of temperatures, radiated heat fluxes, species and dispersed phase concentrations, and NOx emissions.
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