Spray pressure variation effect on the properties of CdS thin films for photodetector applications

Herein, we report the photosensing property of CdS thin films. CdS thin films were coated onto glass substrates via a spray pyrolysis method using different spray pressures. Prepared films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical and photoluminescence spectroscopy. XRD analysis demonstrated the growth of crystalline CdS films with crystallite sizes varying from 26 to 29 nm depending on the pressure. The SEM and EDAX analyses revealed nearly-stoichiometric CdS films with smooth surfaces and slight variation in grain morphology due to pressure changes. Optical measurements showed a direct bandgap varying from 2.37 eV to 2.42 eV due to pressure changes. A photodetector was also fabricated using the grown CdS films; the fabricated photodetector exhibited good performance depending on the spray pressure. A spray pressure of 1.5 GPa resulted in high photoresponsivity and external quantum efficiency.     

Analysis of illumination-intensity-dependent j–V characteristics of ZnO/CdS/CuGaSe2 single crystal solar cells

Current–voltage characteristics of ZnO/CdS/CuGaSe₂ single crystal solar cells measured at room temperature are investigated depending on illumination intensity. The characteristics can be described using the two-diode model, indicating two current transport mechanisms acting in the cells. The first and dominant mechanism is recombination of carriers at the interface between CdS and CuGaSe₂. The second one is recombination in the depletion region, which has been found to have a small effect on the solar cell photovoltaic performance. Both the diode ideality factor and the saturation current density of the dominant diode increase under illumination. A model based on interface recombination can explain these results. This model allows the estimation of diffusion voltage, capture cross-section of holes at the interface and mobility of electrons in the CdS layer.     

Fill factor losses in ZnO/CdS/CuGaSe2 single-crystal solar cells

Current–voltage characteristics of ZnO/CdS/CuGaSe₂ single-crystal solar cells with solar conversion efficiency values of η=3.5%, 6.0%, 6.7% and 9.7% were analyzed using the single diode equation. The effect of each of the achieved parameters on the fill factor was calculated. The calculations revealed that the fill factor reduction due to the series resistance remained below Δff=4.4% under illumination, while this effect would have been much higher if the illumination had not reduced the series resistance markedly. The calculation furthermore revealed that the fill factor reduction due to the shunt resistance remained below Δff=3.6% under illumination. This effect would have been negligible if the illumination had not also reduced the shunt resistance in all studied cells. The increase of the saturation current density under illumination has brought about considerably high fill factor losses (at least Δff=8.3%) in all studied cells. Already the dark saturation current density and the diode ideality factor in such cells have been found to be much higher than the ones in the cells based on CuInSe₂. This seems to be the most substantial restriction to the fill factor, and thus to the performance, of solar cells based on CuGaSe₂. An explanation for this different behavior seems to lie in the different band structures of these cells.     

Frequency dependence of the complex dielectric constant of sodium carboxymethyl cellulose

The dielectric constant, ε′, and dielectric loss, ε″, were determined for three solid carboxymethyl cellulose samples having different levels of substitution and different degrees of polymerization over a frequency range of 0.1 – 10 000 kHz at temperatures from 10–60°C. In contrast to the two relaxation processes, γ and β, previously observed in native cotton cellulose, only one relaxation process within a frequency range of 0.1 – 1 kHz was identified. It was found that the dielectric properties do not only depend on the degree of substitution, but also on the weight-average degree of polymerization and uniformity of distribution.     

Impact of inulin and okara on Lactobacillus acidophilus La-5 and Bifidobacterium animalis Bb-12 viability in a fermented soy product and probiotic survival under in vitro simulated gastrointestinal conditions

The effect of inulin and/or okara flour on Lactobacillus acidophilus La-5 and Bifidobacterium animalis Bb-12 viability in a fermented soy product (FSP) and on probiotic survival under in vitro simulated gastrointestinal conditions were investigated throughout 28 days of storage at 4 °C. Employing a 2² design, four FSP trials were produced from soymilk fermented with ABT-4 culture (La-5, Bb-12, and Streptococcus thermophilus): FSP (control); FSP-I (with inulin, 3 g/100 mL of soymilk); FSP-O (with okara, 5 g/100 mL); FSP-IO (with inulin + okara, ratio 3:5 g/100 mL). Probiotic viabilities ranged from 8 to 9 log cfu/g during the 28 days of storage, and inulin and/or okara flour did not affect the viability of La-5 and Bb-12. Bb-12 resistance to the artificial gastrointestinal juices was higher than for La-5, since the Bb-12 and La-5 populations decreased approximately 0.6 log cfu/g and 3.8 log cfu/g, respectively, throughout storage period. Even though the protective effect of inulin and/or okara flour on probiotic microorganisms was not significant, when compared to a fresh culture, the FSP matrix improved Bb-12 survival on day 1 of storage and may be considered a good vehicle for Bb-12 and could play an important role in probiotic protection against gastrointestinal juices.     

Spectrophotormetric Determination of Quinolinium Acid Esters with 2, 4-Dinitrophenylhydrazine

Carbonyl compound. react with 2, 4-dinitrophtnylhydrazin. to form the corresponding hydrsiones. These hydrazones in the prrsence of lN NaOH give a reddish brown color which can be utilized for colorimatric analysis. This method is used for the spectrophoto-metric determination of quinolinium-6-carboxy-l-metliyl- iodide. Furthermota 2. 4-dinitrophenylhydrazine is utilized to kinetic measurements of the rate of hydrolysie of the quinolinium acid esters.     

Backstepping-based cooperative and adaptive tracking control design for a group of underactuated AUVs in horizontal plan

In this paper, we investigate new implementable cooperative adaptive backstepping controllers for a group of underactuated autonomous vehicles that are communicating with their local neighbours to track a time-varying virtual leader of which the relative position may only be available to a portion of the team members. At the kinematic cooperative control level of the autonomous underwater vehicle, the virtual cooperative controller is basically designed on a proportional and derivative consensus algorithm presented in Ren (2010) Ren, W. (2010). Consensus tracking under directed interaction topologies: Algorithms and experiments. IEEE Transactions on Control Systems Technology, 18, 230–237.[Crossref], [Web of Science ®] , [Google Scholar], which involves velocity information from local neighbours. In this paper, we propose a new design algorithm based on singular perturbation theory that precludes the use of the neighbours’ velocity information in the cooperative design. At the dynamic cooperative control level, calculation of the partial derivatives of some stabilising functions which in turn will contain velocity information from the local neighbours is required. To facilitate the implementation of the cooperative controllers, we propose a command filter approach technique to avoid analytic differentiation of the virtual cooperative control laws. We show how Lyapunov-based techniques and graph theory can be combined together to yield a robust cooperative controller where the uncertain dynamics of the cooperating vehicles and the constraints on the communication topology which contains a directed spanning tree are explicitly taken into account. Simulation results with a dynamic model of underactuated autonomous underwater vehicles moving on the horizontal plane are presented and discussed.     

Studies of electrical and mechanical properties of semiconductive poly(vinyl chloride) compositions

A sample of poly(vinyl chloride) (PVC) and a polar plasticizer consisting of dioctylphthalate (DOP) and triisopropylphenylphosphate (TIPPP) was prepared and found to possess some electrical conductivity. Different samples of PVC compositions were formulated from the PVC-DOP-TIPPP system and also variable proportions of the conductive materials polyaniline or the Ni salt of ethylene glycol bisadipate ester. Dibutyltindilaurate as a heat stabilizer, titanium oxide as a filler, and sandorin red 20 pigment were added. The effect of the structure of polyaniline and Ni adipate ester on the electrical and mechanical properties of the PVC–DOP–TIPPP system was studied to obtain a semiconductive plasticized PVC with good mechanical properties. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 685–693, 1998     

One-pot lithium bromide-catalyzed reaction of polyoxyethylene diglycidyl ether with carbon disulfide: synthesis of new polyoxyethylene epoxyoxathiolane-2-thione

A simple and highly efficient regio- and chemio-specific synthesis of polyoxyethylene epoxyoxathiolan-2-thione was realized from a one-pot reaction of polyoxyethylene diglycidyl ether and carbon disulfide using lithium bromide as a catalyst. The unsymmetrical obtained products were fully characterized by ¹H, ¹³C NMR and high-resolution mass spectra data.