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1.
P. Kavouras Th. Kehagias K. Chrissafis Ph. Komninou Th. Karakostas 《Journal of Thermal Analysis and Calorimetry》2006,86(3):715-719
Three batch compositions of pure oxides (SiO2,
Fe2O3, PbO, Na2O)
with equivalent SiO2, Fe2O3
and PbO contents and a gradually increased Na2O content
were vitrified through heating in a high temperature electric furnace and
subsequent quenching. The resulting vitreous products were thermally treated
in order to study the devitrification behaviour, under conditions designated
from differential thermal analysis experiments. Depending on the Na2O
content, crystal phase separation gave rise to the growth of acmite and hematite
or maghemite. A uniformly phase separated glass-ceramic material, with crystallites
of similar size and population density, was produced from devitrification
of the vitreous product with the higher Na2O content. 相似文献
2.
Ph. Komninou Th. Kehagias A. Delimitis G.P. Dimitrakopulos J. Kioseoglou E. Dimakis A. Georgakilas Th. Karakostas 《Superlattices and Microstructures》2004,36(4-6):509
The structural properties of InN thin films, grown by rf plasma-assisted molecular beam epitaxy on Ga-face GaN/Al2O3(0001) substrates, were investigated by means of conventional and high resolution electron microscopy. Our observations showed that a uniform InN film of total thickness up to 1 μm could be readily grown on GaN without any indication of columnar growth. A clear epitaxial orientation relationship of , was determined. The quality of the InN film was rather good, having threading dislocations as the dominant structural defect with a density in the range of 109–1010 cm−2. The crystal lattice parameters of wurtzite InN were estimated by electron diffraction analysis to be a=0.354 nm and c=0.569 nm, using Al2O3 as the reference crystal. Heteroepitaxial growth of InN on GaN was accomplished by the introduction of a network of three regularly spaced misfit dislocation arrays at the atomically flat interface plane. The experimentally measured distance of misfit dislocations was 2.72 nm. This is in good agreement with the theoretical value derived from the in-plane lattice mismatch of InN and GaN, which indicated that nearly full relaxation of the interfacial strain between the two crystal lattices was achieved. 相似文献
3.
V. Karakostas 《International Journal of Theoretical Physics》1994,33(8):1645-1659
Recently, Ghirardi, Rimini, Weber, and Pearle have proposed a stochastic modification of the Schrödinger equation which dynamically suppresses coherent superpositions of macroscopically distinguishable states and so avoids the infamous cat paradox. We show that the modified dynamics reduces the state vector completely only in the limit of infinite time, and therefore, for any finite timet, no objective local property can be meaningfully assigned to measurement outcomes. Since a physical mechanism giving rise to stochastic spontaneous localizations of the state vector is lacking, we argue that the model (however heuristically interesting) turns out to bead hoc. Finally, we discuss consequences of this latter feature in association with the elusiveness of the two new constants of nature appearing in the model. 相似文献
4.
J E Boylan A A Syntetos G C Karakostas 《The Journal of the Operational Research Society》2008,59(4):473-481
Different stock keeping units (SKUs) are associated with different underlying demand structures, which in turn require different methods for forecasting and stock control. Consequently, there is a need to categorize SKUs and apply the most appropriate methods in each category. The way this task is performed has significant implications in terms of stock and customer satisfaction. Therefore, categorization rules constitute a vital element of intelligent inventory management systems. Very little work has been conducted in this area and, from the limited research to date, it is not clear how managers should classify demand patterns for forecasting and inventory management. A previous research project was concerned with the development of a theoretically coherent demand categorization scheme for forecasting only. In this paper, the stock control implications of such an approach are assessed by experimentation on an inventory system developed by a UK-based software manufacturer. The experimental database consists of the individual demand histories of almost 16?000 SKUs. The empirical results from this study demonstrate considerable scope for improving real-world systems. 相似文献
5.
P. Kavouras M. Katsikini N. Vouroutzis C. B. Lioutas E. C. Paloura J. Antonopoulos Th. Karakostas 《Journal of Crystal Growth》2001,230(3-4):454-458
We study the effect of N+ and O+ implantation on the microhardness and the microstructure of epitaxially grown GaN. The microhardness is measured using a Knoop diamond indenter while information on the effect of implantation on the surface morphology, microstructure and electronic structure is provided by atomic force microscopy, cross-section transmission electron microscopy and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. It is demonstrated that implantation increases the surface microhardness. A possible mechanism for the surface hardening effect is based on the formation of N interstitials that pin the dislocations and prohibit the plastic deformation. In addition to the hardening effect, the implantation induced N interstitials introduce a characteristic resonance in the NEXAFS spectra, at 1.4 eV below the absorption edge. 相似文献
6.
We consider the problem of characterizing user equilibria and optimal solutions for selfish routing in a given network. We
extend the known models by considering malicious behavior. While selfish users follow a strategy that minimizes their individual
cost, a malicious user will use his flow through the network in an effort to cause the maximum possible damage to the overall cost. We define
a generalized model, present characterizations of flows at equilibrium and prove bounds for the ratio of the social cost of
a flow at equilibrium over the cost when centralized coordination among users is allowed.
An extended abstract of this work appeared in the Proceedings of the 14th Annual International Symposium on Algorithms and
Computation (ISAAC) 2003.
G. Karakostas’ research was supported by an NSERC Discovery research grant and MITACS.
Part of this research was done when Viglas was a postdoctoral fellow at the University of Toronto, Canada. 相似文献
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George Karakostas 《Annali di Matematica Pura ed Applicata》1982,131(1):1-27
Summary The translation of abstract causal operators along any function in their domain analogous to the Miller-Sell [21] translation of Volterra integral operators along solutions is established. A skew-product semi-flow with phase- space a convergence space is constructed via the shifting semi- flow and the translations of operators and dynamic properties arising from the nature of the semi- flow are investigated. The restriction of the semi- flow on a specific set is used to define the limiting equations along solutions of causal operator equations of the form x=Tx. Applications are given on implicit Volterra integral equations with an additional delay argument and new results on the asymptotic behavior of the solutions are given.This research was supported by the Deutscher Akademischer Austaunschdienst. 相似文献
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