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991.
Within the framework of the effective-mass approximation and variational approach, we present calculations of the bound exciton binding energy, due to an ionized donor, in wurtzite InxGa1−xN/GaN strained quantum dots (QDs), considering three-dimensional confinement of the electron and hole in the QDs and the strong built-in electric field induced by the spontaneous and piezoelectric polarizations. Our results show that the position of the ionized donor, the strong built-in electric field, and the structural parameters of the QDs have a strong influence on the donor binding energy. The variation of this energy versus position of the donor ion is in double figures of milli-electron volt. Realistic cases, including the donor in the QD and in the surrounding barriers, are considered. 相似文献
992.
The present study concerns magnetic behavior of nanocrystalline Cu–Ni, Cu–Fe and Cu–Ni–Fe alloys prepared by mechanical alloying. It has been found that the magnetic properties e.g. Hc, Mr and Ms of the nanocrystalline alloys were significantly influenced by the changes in microstructural constituents, grain size and evolution of phases. Microstructural changes in the alloys have been effected by carrying out isothermal treatments on the mechanically alloyed products in the temperature range of 450–650 °C. Phase evolution in the samples after the isothermal treatments were identified and characterized by X-ray diffraction (XRD) and differential scanning calorimetric (DSC) techniques and the results were correlated with the magnetic properties of the alloys. 相似文献
993.
George Alyfantis Stathes Hadjiefthymiades Lazaros Merakos 《Mobile Networks and Applications》2006,11(2):241-251
An overlay smart spaces system, called MITOS, is proposed for managing the use of the resources in wireless local area networks
(WLAN). MITOS monitors the traffic load distribution in the different WLAN segments, as well as the location of each user,
and when necessary, suggests to specific users to change their location in order to improve their quality of service. Enhancements
to the basic MITOS architecture are introduced to intelligently manage local congestion, and maintain an almost uniform load
level across the network. The approach used for load balancing is based on game theoretic mechanisms, such as the solutions
to the Santa Fe Bar Problem. Simulation results are provided showing the efficiency of the proposed system.
The research of the author for his PhD studies is supported by the Alexander S. Onassis Foundation Scholarship Programme.
George Alyfantis received his B.Sc. degree in Informatics and Telecommunications from the Department of Informatics and Telecommunications,
University of Athens, Athens Greece, in 2002. He received his M.Sc. degree in Communication and Network Systems from the same
Department, in 2003. Since 2001, he is a member of the Communication Networks Laboratory (CNL) of the University of Athens.
Currently, he is working towards his Ph.D. thesis. His research interests include pervasive/mobile computing, middleware for
wireless sensor networks, web caching performance and game theory. He is the author of 5 papers in the aforementioned areas.
In the course of his studies he received numerous distinctions like the Alexandros Onassis Foundation Scholarship for his
Ph.D. studies, the best student award of the Department of Informatics and Telecommunications for graduating first in his
B.Sc./M.Sc. class and the best M.Sc. thesis Ericsson Award of Excellence in Telecommunications 2004.
Stathes Hadjiefthymiades received his B.Sc. (honors) in Informatics from the Department of Informatics at the University of Athens, Greece, in 1993
and his M.Sc. (honors) in Informatics (Advanced information systems) from the same department in 1996. In 1999 he received
his Ph.D. from the University of Athens (Department of Informatics and Telecommunications). In 2002 he received a joint engineering-economics
M.Sc. degree from the National Technical University of Athens. In 1992 he joined the Greek consulting firm Advanced Services
Group, Ltd., where he was involved in the analysis and specification of information systems and the design-implementation
of telematic applications. In 1995 he became a member of the Communication Networks Laboratory (UoA-CNL) of the University
of Athens. During the period September 2001–July 2002, he served as a visiting assistant professor at the University of Aegean,
Department of Information and Communication Systems Engineering. On the summer of 2002 he joined the faculty of the Hellenic
Open University (Department of Informatics), Patras, Greece, as an assistant professor.
Since December 2003, he is in the faculty of the Department of Informatics and Telecommunications, University of Athens, where
he is presently an assistant professor. He is coordinating the Pervasive Computing Research Group of the Dept. of Informatics
and Telecommunications at the University of Athens. He has participated in numerous projects realized in the context of EU
programs (ACTS, ORA, TAP, and IST), EURESCOM projects, as well as national initiatives. His research interests are in the
areas of web engineering, wireless/mobile computing, and networked multimedia applications. He is the author of over 80 publications
in the above areas.
Lazaros Merakos received the Diploma in electrical and mechanical engineering from the National Technical University of Athens, Athens, Greece,
in 1978, and the M.S. and Ph.D. degrees in electrical engineering from the State University of New York, Buffalo, in 1981
and 1984, respectively. From 1983 to 1986, he was in the faculty of the Electrical Engineering and Computer Science Department
University of Connecticut, Storrs. From 1986 to 1994 he was in the faculty of the Electrical and Computer Engineering Department,
Northeastern University, Boston, MA. During the period 1993–1994, he served as director of the Communications and Digital
Processing Research Center, Northeastern University. During the summers of 1990 and 1991, he was a visiting scientist at the
IBM T. J. Watson Research Center, Yorktown Heights, NY. In 1994, he joined the faculty of the University of Athens, Athens,
Greece, where he is presently a professor in the Department of Informatics and Telecommunications, and director of the Communication
Networks Laboratory (UoA-CNL) and the Networks Operations and Management Center. Since 1995, he is leading the research activities
of UoA-CNL in the area of mobile communications, in the framework of the Advanced Communication Technologies and Services
(ACTS) and Information Society Technologies (IST) programs funded by the European Union (projects RAINBOW, Magic WAND, WINE,
MOBIVAS, POLOS, ANWIRE, E2R, LIAISON). His research interests are in the design and performance analysis of communication
networks, and wireless/mobile communication systems and services. He has authored more than 190 papers in the above areas.
Dr. Merakos is chairman of the board of the Greek Universities Network, the Greek Schools Network, and member of the board
of the Greek Research Network. In 1994, he received the Guanella Award for the best paper presented at the International Zurich
Seminar on Mobile Communications. 相似文献
994.
In the present work, different geometries of interferometers with three divergent illumination beams are discussed. It is shown that the sensitivity components for each source can be measured with a maximum weight factor. The three sources were placed respectively, on x, y and near to z axis of a coordinate system. Based on our theoretical calculations it is proposed an interferometer that uses ESPI technique. Experimental results of displacements and strains are presented for one elastic surface when a torsion load is applied near to the target centre. 相似文献
995.
Studies on Structure and Electrocatalytic Hydrogen Evolution of Nanocrystalline Ni-Mo-Fe Alloy Electrodeposit 总被引:5,自引:0,他引:5
NanocrystallineNi Mo Fealloydepositswereobtainedbyelectrode position .ThestructuresofthealloydepositswereanalyzedbyX raydiffraction (XRD )andX rayphotoelectronspectroscopy(XPS) .TheXRDresultsofnanocrystallineNi Mo Fealloydepositshowthatmanydiffractionlinesdisappear ,andthatthereisonlyonediffractionpeakat 44 .0° .TheXPSresultsofnanocrystallineNi Mo Fealloydepositsindicatethatthenickel,molybdenumandironofthedepositsexistinmetallicstate ,andthatthebindingen ergyofthealloyedelementsincre… 相似文献
996.
A. Kornylo A. Jankowska-Frydel B. Kuklinski M. Grinberg N. Krutiak Z. Moroz M. Pashkowsky 《Radiation measurements》2004,38(4-6):707-710
The influence of Fe and Li co-doping on optical properties of ZnWO4 crystals have been investigated by optical spectroscopy and electron paramagnetic resonance (EPR). The iron ions were added to the ZnWO4 composition in the form of Fe0, FeO or Fe2O3. EPR has been used for determination of the Fe3+ concentration. The luminescence and excitation spectra obtained at different temperatures are presented. Under excitation 325 nm, two bands were observed: blue-green emission peaked at 490 nm and red peaked at 650 nm. The blue- green emission is related to Fe3+ and their shape depends on the doping method. The red emission is not related to the Fe3+. 相似文献
997.
998.
本文用微波溶样技术,对头发样品进行消解处理,用FAAS法测定头发中锌、铜、铁。实验结果表明,用微波溶样消解头发具有省时、节约试剂、消解完全等优点。用本法测定头发中锌、铜、铁,获得满意的方法精密度、准确度。 相似文献
999.
1000.
Cu-Cr alloys, irradiated with a low-energy, high-current electron beam, are analyzed by high-resolution secondary ion mass spectrometry. Mass spectra and images of Cu+ and Cr+ surface distributions finely reveal the regions enriched in Cu and Cr. For electron beam energies above a threshold value, the formation of a non-equilibrium Cu1−xCrx solid solution, extending over sub-micrometer areas is highlighted for the first time. A discussion of the process leading to Cu1−xCrx formation is given. 相似文献