排序方式: 共有26条查询结果,搜索用时 15 毫秒
21.
J. Portier H.S. Hilal I. Saadeddin S.J. Hwang M.A. Subramanian G. Campet 《Progress in Solid State Chemistry》2004,32(3-4):207-217
Thermodynamic parameters and energy-band gap of a given metal oxide, are suitable measures of its stability. For this reason, direct correlations between energy-band gap or chemical hardness, and thermodynamic parameters (e.g. standard enthalpy of formation) have been constructed for different metal oxides. Furthermore, a simple relationship to calculate values of energy-band gaps, for metal oxides, from values of their enthalpies of formation, is presented here. When tested, an appreciable number of metal oxides from s- , p- and d-blocks well obeyed the relationship, while a number of metal oxides deviated. A qualitative theoretical account for such different behaviors is presented here. 相似文献
22.
Vertex Cover: Further Observations and Further Improvements 总被引:5,自引:0,他引:5
Jianer Chen Iyad A. Kanj Weijia Jia 《Journal of Algorithms in Cognition, Informatics and Logic》2001,41(2):280
Recently, there has been increasing interest and progress in lowering the worst-case time complexity for well-known NP-hard problems, particularly for the
Cover problem. In this paper, new properties for the
problem are indicated, and several simple and new techniques are introduced, which lead to an improved algorithm of time O(kn + 1.2852k) for the problem. Our algorithm also induces improvement on previous algorithms for the
problem on graphs of small degree. 相似文献
23.
Doped SnO2 thin films have been prepared by sputtering from two different targets: antimony doped tin oxide (ATO) and antimony and zinc doped tin oxide (AZTO). In the case of ATO ceramic, the antimony amount only reaches 0.012 mol per formula unit due to its evaporation at high temperature while the presence of Zn2+ in AZTO prevents the antimony evaporation, greatly enhances the ceramic density and allows the deposition of thin films with a high deposition rate. Both types of thin films have a dense morphology with a smooth surface and they are polycrystalline. For post-annealed ATO thin films, the Drude model was applied to deduce the carrier concentration, the optical mobility as well as the resistivity. The carrier concentration is around ten times higher for ATO thin films compared to AZTO. The two combined effects (higher carrier concentration and mobility) for ATO thin films doped with 1.2% of Sb lead to the best optoelectronic performances, confirming previous results obtained with ceramics. Nevertheless, we have a better opportunity to modulate the conductivity in the case of AZTO thin films. 相似文献
24.
Iyad Karamé Dr. Malika Boualleg Jean‐Michel Camus Dr. Tarun K. Maishal Dr. Johan Alauzun Dr. Jean‐Marie Basset Dr. Christophe Copéret Dr. Robert J. P. Corriu Prof. Dr. Erwan Jeanneau Dr. Ahmad Mehdi Prof. Dr. Catherine Reyé Prof. Dr. Laurent Veyre Chloé Thieuleux Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(44):11820-11823
25.
Hichem Mrabet Author Vitae Iyad Dayoub Author Vitae Rabah Attia Author Vitae Walaa Hamouda Author Vitae 《Optics Communications》2010,283(21):4234-4241
In this paper, we report the modal dispersion of silica graded-index optical fibers as a function of the input mode parameters and lunching conditions in local area network (LAN) context. In that, we examine the mode-depending parameters, namely, modal delay, modal attenuation and mode-coupling effects as a function of wavelength. We show that the number of excited mode groups depends strongly on the spot beam radius when the fiber is excited with an axial Gaussian beam where we find an optimal axial diameter exciting only two mode groups. We present a comparison of the number of excited mode groups, the optimal spot radius beam, the signal penalty and the 3-dB baseband bandwidth enhancement for the optimal axial launching compared with full mode excitation, offset launching and mode-field matched axial launching. 相似文献
26.
Mohammed Azmi Al-Betar Iyad Abu DoushAhamad Tajudin Khader Mohammed A. Awadallah 《Applied mathematics and computation》2012,218(10):6095-6117
Selection is a vital component used in Evolutionary Algorithms (EA) where the fitness value of the solution has influence on the evolution process. Normally, any efficient selection method makes use of the Darwinian principle of natural selection (i.e., survival of the fittest). Harmony search (HS) is a recent EA inspired by musical improvisation process to seek a pleasing harmony. Originally, two selection methods are used in HS: (i) memory consideration selection method where the values of the decision variables are randomly selected from the population (or solutions stored in harmony memory (HM)) to generate a new harmony, and (ii) selecting a new solution in HM whereby a greedy selection is used to update the HM. The memory consideration selection, the focal point of this paper, is not based on natural selection principle which draws heavily on random selection. In this paper, novel selection schemes which replace the random selection scheme in memory consideration are investigated, comprising global-best, fitness-proportional, tournament, linear rank and exponential rank. The proposed selection schemes are individually altered and incorporated in the process of memory consideration and each adoption is realized as a new HS variation. The performance of the proposed HS variations are evaluated and a comparative study is conducted. The experimental results using benchmark functions show that the selection schemes incorporated in memory consideration directly affect the performance of HS algorithm. Finally, a parameter sensitivity analysis of the proposed HS variations is analyzed. 相似文献