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Various metal oxide-silica nanocomposite films have been recently proposed as gas-sensitive materials. This paper presents results on cobalt oxide-SiO2 mesoporous nanocomposite thin films templated by a cationic surfactant. The films were deposited on glass substrate by dip-coating process, using [Co(CH3COO)2]·4H2O and tetraethoxysilane (TEOS) as starting materials. The effect of withdrawal speed, number of layers and thermal treatment on the crystalline structure, morphology, Co-doping states, optical, electrical and gas sensing properties of the thin films has been investigated using X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, optical transmittance and room temperature photoreduction-oxidation data. © 2007 Elsevier B.V. All rights reserved.

Transparent wide band gap indium molybdenum oxide (IMO) thin films were rf sputtered on glass substrates at room temperature. The films were studied as a function of sputtering power (ranging 40-180 W) and sputtering time (ranging 2.5-20 min). The film thickness was varied in the range 50-400 nm. The as-deposited films were characterized by their structural (XRD), morphological (AFM), electrical (Hall Effect measurements) and optical (visible-NIR spectroscopy) properties. XRD studies revealed that the films are amorphous for the sputtering power ≤ 100 W and the deposition time ≤ 5 min, and the rest are polycrystalline with a strong reflection from (222) plane showing a preferential orientation. A minimum bulk resistivity of 2.65 × 10- 3 Ω cm and a maximum carrier concentration of 4.16 × 1020 cm- 3 are obtained for the crystalline films sputtered at 180 W (10 min). Whereas a maximum mobility (19.5  cm2 V- 1 s- 1) and average visible transmittance (∼ 85%) are obtained for the amorphous films sputtered at 80 W and 100 W respectively for 10 min. A minimum transmittance (∼ 18%) was obtained for the crystalline films sputtered at 180 W (∼ 305 nm thick). The optical band gap was found varying between 3.75 and 3.90 eV for various sputtering parameters. The obtained results are analyzed and corroborated with the structure of the films. © 2007 Elsevier B.V. All rights reserved.

This paper reports on a method and a test setup developed to measure the transient dark current and the spectral response characteristics of a-Si:H MIS photosensors. Using this method the segmented-gate/SiNx/a Si:H/n +/ITO structures have been characterized under different biasing conditions. The dependences of the dark and light signals on the refresh pulse amplitude, offset voltage and pulse width were measured and analyzed. It is found that the amplitude of the time-dependent component of the leakage current associated with charge trapping at the insulator-semiconductor interface can be significantly reduced by adjusting the offset voltage. The observed bias dependence of the spectral response characteristics is explained by analyzing the charge carrier transport in the absorption layer at different wavelengths of the incident light. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA.

Co-doped TiO 2 films were characterized by spectroscopic ellipsometry to determine their thickness, deposition rate and optical properties as function of substance temperature and background gas composition. To fit the data we used a combination of a single Tauc-Lorentz oscillator with the Drude free electron model to take in account the free electrons present in the film. The Co doping and addition of H 2 to the gas phase during film growth cause the formation of a titanium oxide which containsfree electrons that absorb the energy of the red part of the spectrum, causing k to increase. The n of the film at 1.5 eV is about 2.3 eV. The fittings also show that the n of films decreases and k increase at the surface. This can be related to a segregation of Co to the surface, which in some cases, of high substrate temperature and high H 2 flow during deposition, can lead to and even higher concentration of free electrons at the surface. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA.

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We present a first theoretical determination of the hyperfine coupling constants of a spherical top molecule using ab initio methods. The scalar and tensorial contributions to the spin-rotation constants and the diamagnetic and paramagnetic contributions to the nuclear shielding constant are calculated for the ³²SF₆ molecule. The corrections to the spin-rotation constants due to nuclear Thomas precession are evaluated and discussed. Our results are compared with previously reported experimental values.

We present a first theoretical determination of the hyperfine coupling constants of a spherical top molecule using <i>ab initio</i> methods. The scalar and tensorial contributions to the spin-rotation constants and the diamagnetic and paramagnetic contributions to the nuclear shielding constant are calculated for the ³²SF₆ molecule. The corrections to the spin-rotation constants due to nuclear Thomas precession are evaluated and discussed. Our results are compared with previously reported experimental values.

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To evaluate the evolution of a dark film formation on silver surface objects, several coupons were catalogued and place inside a museum, located in an urban area. The changes on these samples were measured by spectroscopic ellipsometry, in periods of months. This technique allows the reduction of the coupons exposure time, in several months, due to its high sensitivity to surface modifications, with acceptable results for the evaluation of its degradation. The thicknesses of the degradation layers and the optical properties of silver oxide, chloride and sulphide reference samples were determined using a mixture of Tauc-Lorentz and Drude models. The composition of the silver corrosion layer was determined by fitting the layer using a Bruggeman Effective Medium Approximation (BEMA) of the three products plus voids. It was found that the thickness of the layer depends in the placement of the coupons, namely, inside or outside displayers. The average film thickness after 6 months was of 180 Å and 280 Å, inside and outside the displayers, respectively. The main compounds found in the layers were the silver chlorides and sulphides, which composition changed with the thickness of the layer, and the exposition time. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.

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This paper presents the design of a test rig for an all HTS linear synchronous motor. Although this motor showed to have several unattractive characteristics, its design raised a number of problems which must be considered in future HTS machines design. HTS electromagnetic properties led to the development of new paradigms in electrical machines and power systems, as e. g. in some cases iron removal and consequent assembly of lighter devices. This is due to superconductor's ability to carry high currents with minimum losses and consequent generation in the surrounding air of flux densities much higher than the allowed by ferromagnetic saturation. However, severe restrictions in HTS power devices design that goes further beyond cryogenic considerations must be accounted in. This is usually the case when BSCCO tapes are used as conductors. Its bending limitations and the presence of flux components perpendicular to tape surface, due to the absence of iron, have to be considered for it may turn some possible applications not so attractive or even practically unfeasible. An all HTS linear synchronous motor built by BSCCO tapes as armature conductors and two trapped-flux YBCO bulks in the mover was constructed and thrust force measurements are starting to be performed. Although the device presents severe restrictions due to the exposed and other reasons, it allowed systematising its design. A pulsed-field magnetiser to generate opposite fluxes for both YBCO bulks is also detailed. Thrust force numerical predictions were already derived and presented.

This paper presents the design of a test rig for an all HTS linear synchronous motor. Although this motor showed to have several unattractive characteristics, its design raised a number of problems which must be considered in future HTS machines design. HTS electromagnetic properties led to the development of new paradigms in electrical machines and power systems, as e. g. in some cases iron removal and consequent assembly of lighter devices. This is due to superconductor's ability to carry high currents with minimum losses and consequent generation in the surrounding air of flux densities much higher than the allowed by ferromagnetic saturation. However, severe restrictions in HTS power devices design that goes further beyond cryogenic considerations must be accounted in. This is usually the case when BSCCO tapes are used as conductors. Its bending limitations and the presence of flux components perpendicular to tape surface, due to the absence of iron, have to be considered for it may turn some possible applications not so attractive or even practically unfeasible. An all HTS linear synchronous motor built by BSCCO tapes as armature conductors and two trapped-flux YBCO bulks in the mover was constructed and thrust force measurements are starting to be performed. Although the device presents severe restrictions due to the exposed and other reasons, it allowed systematising its design. A pulsed-field magnetiser to generate opposite fluxes for both YBCO bulks is also detailed. Thrust force numerical predictions were already derived and presented.

This paper presents the design of a test rig for an all HTS linear synchronous motor. Although this motor showed to have several unattractive characteristics, its design raised a number of problems which must be considered in future HTS machines design. HTS electromagnetic properties led to the development of new paradigms in electrical machines and power systems, as e. g. in some cases iron removal and consequent assembly of lighter devices. This is due to superconductor's ability to carry high currents with minimum losses and consequent generation in the surrounding air of flux densities much higher than the allowed by ferromagnetic saturation. However, severe restrictions in HTS power devices design that goes further beyond cryogenic considerations must be accounted in. This is usually the case when BSCCO tapes are used as conductors. Its bending limitations and the presence of flux components perpendicular to tape surface, due to the absence of iron, have to be considered for it may turn some possible applications not so attractive or even practically unfeasible. An all HTS linear synchronous motor built by BSCCO tapes as armature conductors and two trapped-flux YBCO bulks in the mover was constructed and thrust force measurements are starting to be performed. Although the device presents severe restrictions due to the exposed and other reasons, it allowed systematising its design. A pulsed-field magnetiser to generate opposite fluxes for both YBCO bulks is also detailed. Thrust force numerical predictions were already derived and presented.

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The spread of systems that provide parallelism either ‘‘in-the-large’’ (grid infrastructures, clusters) or ‘‘in-the-small’’ (multi-core chips), creates new opportunities for exploiting parallelism in a wider spectrum of application domains. However, the increasing complexity of parallel and distributed platforms renders the programming, the use, and the management of these systems a costly endeavor that requires advanced expertise and skills. Therefore, there is an increasing need for powerful support tools and environments that will help end-users, application programmers, software engineers and system administrators to manage the increasing complexity of parallel and distributed platforms.

The spread of systems that provide parallelism either «in-the-large» (grid infrastructures, clusters) or «in-the-small» (multi-core chips), creates new opportunities for exploiting parallelism in a wider spectrum of application domains. However, the increasing complexity of parallel and distributed platforms renders the programming, the use, and the management of these systems a costly endeavor that requires advanced expertise and skills. Therefore, there is an increasing need for powerful support tools and environments that will help end-users, application programmers, software engineers and system administrators to manage the increasing complexity of parallel and distributed platforms.

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