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1.
A carbon paste electrode (graphite, ion-exchange polymer, transition cations, buffer electrolyte) was achieved and the properties of the compounds were studied. The range of pH over which the metallic cation is most fixed on the polymer was determined. Electronic conductivity measurements of the samples show that their resistance increases greatly when the ratio of polymerised active material exceeds 50%. 相似文献
2.
This paper introduces genetic algorithms for the jump number scheduling problem. Given a set of tasks subject to precedence constraints, the problem is to construct a schedule to minimize the number of jumps. We show that genetic algorithms outperform the previously known Knuth and Szwarcfiter's exhaustive search algorithm when applied to some classes of orders in which no polynomial time algorithms exist in solving the jump number problem. Values for various parameters of genetic jump number algorithms are tested and results are discussed. 相似文献
3.
A high resolution (0.0018 cm−1) Fourier transform instrument has been used to record the spectrum of an enriched 34S (95.3%) sample of sulfur dioxide. A thorough analysis of the ν2, 2ν2 − ν2, ν1, ν1 + ν2 − ν2, ν3, ν2 + ν3 − ν2, ν1 + ν2 and ν2 + ν3 bands has been carried out leading to a large set of assigned lines. From these lines ground state combination differences were obtained and fit together with the existing microwave, millimeter, and terahertz rotational lines. An improved set of ground state rotational constants were obtained. Next, the upper state rotational levels were fit. For the (0 1 0), (1 1 0) and (0 1 1) states, a simple Watson-type Hamiltonian sufficed. However, it was necessary to include explicitly interacting terms in the Hamiltonian matrix in order to fit the rotational levels of the (0 2 0), (1 0 0) and (1 0 1) states to within their experimental accuracy. More explicitly, it was necessary to use a ΔK = 2 term to model the Fermi interaction between the (0 2 0) and (1 0 0) levels and a ΔK = 3 term to model the Coriolis interaction between the (1 0 0) and (0 0 1) levels. Precise Hamiltonian constants were derived for the (0 0 0), (0 1 0), (1 0 0), (0 0 1), (0 2 0), (1 1 0) and (0 1 1) vibrational states. 相似文献
4.
B.D. Ngom T. Mpahane O. Nemraoui J.B. Kana M. Maaza A.C. Beye 《Applied Surface Science》2009,255(7):4153-4158
Novel highly c-oriented tungsten-doped zinc oxide (WZO) thin films with 1 wt% were grown by pulsed laser deposition (PLD) technique on corning 1737F glass substrate. The effects of laser energy on the structural, morphological as well as optical transmission properties of the films were studied. The films were highly transparent with average transmittance exceeding 87% in the wavelength region lying between 400 and 2500 nm. X-ray diffraction analysis (XRD) results indicated that the WZO films had c-axis preferred orientation with wurtzite structure. Film thickness and the full width at half maximum (FWHM) of the (0 0 2) peaks of the films were found to be dependent on laser fluence. The composition determined through Rutherford backscattering spectroscopy (RBS) appeared to be independent of the laser fluence. By assuming a direct band gap transition, the band gap values of 3.36, 3.34 and 3.31 eV were obtained for corresponding laser fluence of 1, 1.7 and 2.7 J cm−2, respectively. Compared with the reported undoped ZnO band gap value of 3.37 eV, it is conjectured that the observed low band gap values obtained in this study may be attributable to tungsten incorporation in the films as well as the increase in laser fluence. The high transparency makes the films useful as optical windows while the high band gap values support the idea that the films could be good candidates for optoelectronic applications. 相似文献
5.
H. GaviB.D. Ngom A.C. BeyeA.M. Strydom V.V. Srinivasu M. ChakerN. Manyala 《Journal of magnetism and magnetic materials》2012,324(6):1172-1176
Low field microwave absorption (LFMA) measurements at 9.4 GHz (X-band), were carried out on pulse laser deposited (PLD) polycrystalline B20 cubic structure FeSi thin film grown on Si (111) substrate. The LFMA properties of the films were investigated as a function of DC field, temperature, microwave power and the orientation of DC field with respect to the film surface. The LFMA signal is very strong when the DC field is parallel to the film surface and vanishes at higher angles. The LFMA signal strength increases as the microwave power is increased. The LFMA signal disappears around 340 K, which can be attributed to the disappearance of ferromagnetic state well above room temperature in these films. We believe that domain structure evolution in low fields, which in turn modifies the low field permeability as well as the anisotropy, could be the origin of the LFMA observed in these films. The observation of LFMA opens the possibility of the FeSi films to be used as low magnetic field sensors in the microwave and rf frequency regions. 相似文献
6.
B.D. Ngom M. ChakerN. Manyala B. LoM. Maaza A.C. Beye 《Applied Surface Science》2011,257(14):6226-6232
We report on the effects of glass substrate temperature on the crystal structure and morphology of tungsten (W)-doped ZnO nanostructures synthesized by pulsed-laser deposition. X-ray diffraction analysis data shows that the W-doped ZnO thin films exhibit a strongly preferred orientation along a c-axis (0 0 0 L) plane, while scanning electron and atomic force microscopes reveal that well-aligned W-doped ZnO nanorods with unique shape were directly and successfully synthesized at substrate temperature of 550 °C and 600 °C without any underlying catalyst or template. Possible growth mechanism of these nanorods is suggested and discussed. 相似文献
7.
8.
M. Maaza B. D. Ngom S. Khamlich J. B. Kana Kana P. Sibuyi D. Hamidi S. Ekambaram 《Journal of nanoparticle research》2012,14(2):714
The possibility of synthesizing binary oxides nanoparticles in a nano-scaled form by laser liquid solid interaction using
a NdYAG “1.064 μm” as an irradiating laser source is reported. The case of MoO3−δ is emphasized. Furthermore, it is demonstrated that the Mo–O electronic valence can be controlled through the coupling effects
of oxygen enriched nature of the used coating liquid layer, namely pure H2O or H2O2 and the laser beam fluence. Dark blue hydrated molybdic pentoxide Mo2O5·xH2O and yellow molybdenum trioxide MoO3 nano-suspensions were reproducibly synthesized with hydrogen peroxide and water, respectively, at a relatively high ablation
rate. The average size of the molybdenum trioxide nanoparticles was about <ϕ>~8 nm, slightly larger than the molybdic pentoxide
ones “<ϕ>~6.2 nm”. 相似文献
9.
A.Y. Fasasi B.D. Ngom J.B. Kana-Kana M. Maaza U. Buttner 《Journal of Physics and Chemistry of Solids》2009,70(10):1322-1329
The results of gadolinium (Gd)-doped barium titanate (BaTiO3) thin films prepared by laser ablation on glass and silicon substrates are reported. Rutherford backscattering (RBS) analyses carried out on glass samples indicated the substitution of barium (Ba) by gadolinium (Gd) after annealing, leading to a film with composition Ba0.76TiGd0.01O2.5. There is a reduction in the thickness from 2.21 to 2.02 microns for as-deposited and annealed films. The films on silicon showed a higher degree of crystallinity compared to that of glass substrates due to increased annealing temperature. The average grain size calculated using the X-ray diffraction (XRD) pattern from silicon substrates was 30 nm. The film has a tetragonal structure with a “c/a” ratio of 1.03 signifying that the incorporation of Gd in BaTiO3 led to the elongation of the c-axis. The percentage transmittance reduced from 80 to 50% due to annealing and this is probably due to structural changes in the film. Swanepoel envelope method employed on the interference fringes of the transmittance pattern led to the determination of the variation of the refractive index with wavelength. Sellmier single oscillator model was applied to determine the optical constants of the films on glass substrates. Bandgap analyses carried out showed the reduction in bandgap with annealing and also the possibility that Gd incorporation has modified the film chemistry leading to the existence of direct (4.35 eV) and indirect (3.88 eV) allowed transitions in the annealed films. Dielectric property measurement carried out under ambient conditions gave a relaxation time τ of 1.6×10−4 s and conduction by small polaron with the onset of polaron conduction set at about 7 kHz. It is conjectured that these properties, especially the high refractive index and the high bandgaps, can make Gd-doped BaTiO3 a good candidate for optoelectronic applications. 相似文献
10.
W-doped ZnO nanostructures were synthesized at substrate temperature of 600 °C by pulsed laser deposition (PLD), from different wt% of WO3 and ZnO mixed together. The resulting nanostructures have been characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy and photoluminescence for structural, surface morphology and optical properties as function of W-doping. XRD results show that the films have preferred orientation along a c-axis (0 0 L) plane. We have observed nanorods on all samples, except that W-doped samples show perfectly aligned nanorods. The nanorods exhibit near-band-edge (NBE) ultraviolet (UV) and violet emissions with strong deep-level blue emissions and green emissions at room temperature. 相似文献