Stability of electrical properties in polyaniline-polystyrene blends

The thermal stability of free standing polystyrene-polyaniline-DiOHP blend electrical properties is described. Electrical conductivity measurements have been performed at different temperatures for a long degradation time. A good stability with time and temperature is observed. The electrical conductivity variations versus temperature are explained on the assumption of a main contribution of hopping mechanisms between conducting clusters.     

Effect of metal oxide nanofluids on the performance of passive solar still single slope for two different absorbent plates

This study aims to improve the performances of a solar still single slope using metal oxide nanofluid (Al₂O₃–water, Cu₂O–water, and TiO₂–water). The numerical study was carried out for the climatic conditions of Agadir, Morocco, with different concentrations of nanofluids inside a basin equipped with an absorber plate with two different absorptivities. The numerical study is based on thermal balance equations applied on different solar system components and solved using the Runge Kutta method. The numerical model is validated by comparing our results with the literature available data. A comparison study of the effect of these nanofluids on solar still productivity is done. The results show that the productivity of the solar still using nanoparticles Cu₂O, TiO₂, and Al₂O₃ are 7.38, 7.1, and 7.064 kg m⁻² day⁻¹, respectively. It is obtained that the maximum efficiency of the solar still is found to be 55.27% by using cuprous oxide nanoparticles. Furthermore, an enhancement in solar still productivity of 6.36%, 19.54%, and 33.25% is obtained by dispersing 1%, 3%, and 5% volume fraction of Cu₂O nanoparticles in pure water, respectively compared to the conventional solar. Moreover, the impact of the absorptivity of the absorber plate on the solar still effectiveness is investigated. Two types of coatings are considered to change the absorber plate absorptivity. The results indicate that the efficiencies of the solar system are 58.81% and 51.77% using an absorber plate with 0.95 and 0.85 of absorptivity, respectively.     

Experimental and numerical study of granular medium-rough wall interface friction

Wall roughness plays a crucial role in granular medium - rough wall interface friction. In this study, an experimental device has been designed to study the influence of boundary conditions, more specifically wall roughness, on the behavior of sheared granular medium. The study is based on use of an analog model, and consists of simulating roughness by means of notches and grains in the medium by monodisperse beads and on use of a numerical model based on the discrete element method. The test protocol entails displacing at fixed speed notched rods under confined granular medium. Movement of the beads layer near the rods as well as friction of the beads against the rods are both studied herein. Results indicate that the parameter controlling friction at the granular medium - rough wall interface is primarily the depth of beads embedment in surface asperities. The objective of the associated numerical modeling is to supplement the experimental results.     

Influence of Alumina-Supported M–Pt Catalysts in DeNOx Reactions with M = Pd or Ir or Ru

To better understand N₂ formation in the selective catalytic reduction of NO _x by propene under oxidative atmosphere, we studied the catalytic behavior of bimetallics. Surface segregation phenomena may provoke geometric and electronic modifications of the catalytic active sites. To explain our results we invoked: (i) the facile way to oxidize the bimetallic aggregates, (ii) the presence of atoms with low coordination number able to be oxidized first and (iii) an eventual formation of like vic-diNO _x species on such bimetallics leading to N₂ formation.     

Electrical properties of polyaniline–polystyrene blends above the percolation threshold

Blends of conductive polymers with classical ones can exhibit good mechanical properties and good electrical conductivity and deserve great attention for application in electronic industrial technology. Conductive polyaniline solutions have been chemically prepared using bis(2-ethyl hexyl)hydrogen phosphate (DiOHP) as the dopant chemical species. The codissolution method leads to conductive polyaniline–polystyrene (PANI–PSt) composites with good mechanical properties. The dependence of electrical conductivity on the volume fraction of PANI in the blend is found to be characteristic of a percolation system. Electrical conductivity and thermoelectric power measurements are interpreted on the basis of hopping mechanisms between polaronic clusters. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1205–1208, 1998     

Dielectric/metal/dielectric structures using copper as metal and MoO3 as dielectric for use as transparent electrode

Transparent conductive oxide/metal/oxide, where the oxide is MoO₃ and the metal is Cu, is realized and characterized. The films are deposited by simple joule effect. It is shown that relatively thick Cu films are necessary for achieving conductive structures, what implies a weak transmission of the light. Such large thicknesses are necessary because Cu diffuses strongly into the MoO₃ films. We show that the Cu diffusion can be strongly limited by sandwiching the Cu layer between two Al ultra-thin films (1.4 nm). The best structures are glass/MoO₃ (20 nm)/Al (1.4 nm)/Cu (18 nm)/Al (1.4 nm)/MoO₃ (35 nm). They exhibit a transmission of 70% at 590 nm and a resistivity of 5.0 · 10^− 4 Ω cm. A first attempt shows that such structures can be used as anode in organic photovoltaic cells.     

Investigation of low resistance transparent MoO3/Ag/MoO3 multilayer and application as anode in organic solar cells

Depending on the resistivity and transmittance, transparent conductive oxides (TCO) are widely used in thin film optoelectronic devices. Thus doped In₂O₃ (ITO), ZnO, SnO₂ are commercially developed. However, the deposition process of these films need sputtering and/or heating cycle, which has negative effect on the performances of the organic devices due to the sputtering and heat damages. Therefore a thermally evaporable, low resistance, transparent electrode, deposited onto substrates room temperature, has to be developed to overcome these difficulties. For these reasons combination of dielectric materials and metal multilayer has been proposed to achieve high transparent conductive oxides. In this work the different structures probed were: MoO₃ (45 nm)/Ag (x nm)/MoO₃ (37.5 nm), with x = 5-15 nm. The measure of the electrical conductivity of the structures shows that there is a threshold value of the silver thickness: below 10 nm the films are semiconductor, from 10 nm and above the films are conductor. However, the transmittance of the structures decreases with the silver thickness, therefore the optimum Ag thickness is 10 nm. A structure MoO₃ (45 nm)/Ag (10 nm)/MoO₃ (37.5 nm) resulted with a resistivity of 8 × 10^− 5 Ω cm and a transmittance, at around 600 nm, of 80%. Such multilayer structure can be used as anode in organic solar cells according to the device anode/CuPc/C₆₀/Alq₃/Al. We have already shown that when the anode of the cells is an ITO film the introduction of a thin (3 nm) MoO₃ layer at the interface anode (ITO)/organic electron donor (CuPc) allows reducing the energy barrier due to the difference between the work function of ITO and the highest occupied molecular orbital of CuPc [1]. This property has been used in the present work to achieve a high hole transfer efficiency between the CuPc and the anode. For comparison MoO₃/Ag/MoO₃/CuPc/C₆₀/Alq₃/Al and ITO/MoO₃/CuPc/C₆₀/Alq3/Al solar cells have been deposited in the same run. These devices exhibit efficiency of the same order of magnitude.     

Electrical characterisation of CuInSe2 thin films for solar cells applications

Nearly stoichiometric large area polycrystalline CuInSe, thin films have been grown using a simple and low cost method based on close-spaced vapour transport (CSVT) in a vertical closed tube. Direct current electrical conductivity, Hall coefficient and thermoelectric power measurements have been performed as a function of the temperature in the range 80–600 K. Results are interpreted on the basis of conduction due to hopping mechanisms in an impurity band and, at high temperatures, due to diffusion mechanisms in the extended states of the valence and conduction bands.     

Spatial and temporal variations of niphargus populations in interstitial aquatic habitat at the karst/floodplain interface

Artificial substrates buried in stream sediments at the karst/floodplain interface were used to examine the spatial and temporal variations of Niphargus populations. The study was carried out at two stations in two different areas of the French Jura. One was mainly supplied by karst water (Verna station), the other by both karst and surface waters (Pissoir station). The occupation of interstitial habitat was found to depend on several interacting factors:

• 1 The waterflow and its changes at the outlet. The correlation between abundance of individuals and discharge was strongest with the discharges two to four days before sampling. The structure and restoration of populations after a spate related to geological characteristics. In particular, restoration was slower and more difficult in the sediments located at the base-level of a massif (Verna) than at an overflow level (Pissoir).
• 2 The location of the sediments. At the Pissoir station, the number of individuals was higher at the main outflow, but also for both stations, on the banks opposite the outlet. Animals drifting from the karst system found refuge in the sediment of the opposite bank. Almost no Niphargus were found upstream from the outlets. At the Verna station, Niphargus were only found inside the cave.
• 3 The variability of the number of animals at different depths in the sediment was more difficult to explain. At the station mainly supplied by karst water, which presented a relatively constant flow during the study, the distribution seemed to be random. At the other station, where discharge varied considerably, the vertical distribution globally presented a gradient in abundance with more individuals in the upper sediment level. This gradient varied according to the samples. Discharge changes partly explained these results.

     

Human tracking using joint color-texture features and foreground-weighted histogram

Multimedia Tools and Applications - This paper proposes a new appearance model for human tracking based on Mean Shift framework. The proposed method uses a novel target representation by using...