This paper presents the result of thermodynamic studies on (Se80Te20)100-xAgx ( 1< x < 4)glasses under non isothermal conditions using differential scanning calorimetric technique. Thecrystallization kinetics has also been discussed. Thermodynamic parameters like entropy difference betweenglassy and the crystalline phase, difference of Gibbs free energy, specific heat, and the enthalpy released during phase transformation have been evaluated. The heat capacity jump and fragility of these alloys are alsocalculated. The results show that the stability of sample is minimum for (Se80Te20)99Ag1 and maximum for (Se80Te20)97Ag3 among all the samples.

Based on the features of diode-pumped Yb3+:Y2SiO5 (Yb:YSO) lasers, a thermal model was established. According to the latest reports and measurements on thermal parameters, and further considering the heat transfer on side surface, thermal lensing effect of Yb:YSO was studied for the first time to our knowledge. Under the pump power of 17 W, the maximum temperature (488.4 °C) and the maximum distortion (1.24 μm) were obtained by solving Poisson equation using finite difference method. Moreover, thermal lens focal length was measured through a plane-plane cavity. All the results demonstrate that the theoretical result will be closer to the reality if we take the heat transfer on side surfaces into account.

An insertable electron beam ionizer into a quadrupole-based secondary ion mass spectrometer instrument has been designed and installed to analyze sputtered neutrals. The optimum design conditions of the ionizer have been obtained by modeling various configurations of the system using a simulation program developed by us. The program has allowed us to compute the potentials and ion trajectories inside the system to test the performance of the ion optics design. We have investigated the advantages of using a large ionization volume with low electron current to minimize the space charge effect in the ionizer, as this is the majorproblem in this type of instrument. In addition, we have used the simulations to obtain allelectrodes voltages which provide an efficient suppression of residual gas and secondaryions. A good useful yield was obtained, even with low electron densities, thanks to the highgeometrical acceptance of the ionizer and its large active volume. This configurationimplies less thermal radiation in the ionizer and, in addition, a longer life time of thefilament. Although the signal of residual gas not suppressed (i.e. in residual gasmode) is two orders of magnitude higher than the signal of sputtered neutrals, we haveachieved a good background suppression.

A systematic investigation on growth and sensor characteristics of SnO2 thin films of different orientations is reported for the first time. Thin films were grown by pulsed laser (KrF; λ = 248 nm) ablation technique under in-situ conditions. Films deposited at 525 °C on (1102) sapphire were predominantly (101) orientated whereas those deposited on (100) LaAlO3 were highly a-axis orientated. Sensors made of predominantly (101) oriented films exhibited more than two orders magnitude change in resistance even for 100 ppm of H2 in air at 310 °C. The response and retracing times of the sensor were remarkably short respectively 30 and 200 s. Sensors made of a-axis oriented films also exhibited similar sensitivity and response time for the same quantity of both H2 and LPG. However, the retrace time was very long typically about 20 min. Atomic force microscopic (AFM) investigation reveals that the films are highly granular with an average size of about 100–150 nm which is ten times larger than the critical size of 6 nm, a criterion required for high sensitivity. (The Debye length of ${\rm SnO}_2 \cong3.07$  nm at 293 K and the critical grain size is therefore 2 × Debye length, whichis 6 nm.)

The aim of this work is to study the kerosene explosibility in closed or vented vessels and to develop an application to safety systems. The basic characteristics of the model have been developed for the ignition and the combustion of propulsive powders and adapted to liquid fuels with appropriate parameters linked to simplified kinetics. A simple representation of the combustion phenomena based on energy transfers and the action of specific molecular species is presented. The pressure venting, due to the vent breaking is calculated taking into account the mass rate of discharge of the different products in the assumption of the standard orifice equations.The model allows the study of various parameters such as the nature of the kerosene, the fuel ratio of the mixture, the ignition energy, the thermal exchanges and the influence of the pressure venting or the vent area. The theoretical results have been compared with data obtained in the course of experiments performed in small vessel volumes (V 0 = 13 and 33 l) and indicate correct preliminary tendencies.

The presence of impurities in the molecular crystals of organic semiconductors is a key limiting factor for the performance of related electronic devices. For this reason, the atomic-scale details of impurity incorporation are important elements for modeling and optimization of organic electronic systems. In this article, we use first-principles density-functional theory calculations to describe the vibrational spectrum of typical impurity culprits in the prototype organic semiconductor pentacene. First, we validate the computational approach by comparing results on vibrational modes of impurity-free pentacene with available theoretical and experimental data. We then analyze the effect of oxygen, water, and hydrogen impurities on the modes of pentacene crystals. The results identify distinct impurity-related features which can help understand the evolution of impurities in pentacene samples.

Schottky barrier diodes based on a composite of polyaniline with titanium oxide (TiO2) were fabricated using aluminum as a Schottky contact and gold as an ohmic contact. The observed current-voltage characteristics can be satisfactorily fitted using the modified Schottky equation. The current-voltage characteristics were studied to explain the rectification generation of the diode. The diode shows non-ideal I-V behavior with an ideality factor greater than unity. The conduction mechanism was determined and a Schottky-type conduction process was defined. The diode parameters such as saturation current density and ideality factor were found to be 9.28 x 10−4 A/cm2 and 6.33, respectively.

The plasma parameters for the fast deposition of highly crystallized microcrystalline silicon (µc-Si) films with low defect density are presented using a high-density and low-temperature SiH4-H2 mixture microwave plasma. A very high deposition rate of $\sim $ 65 Å/s was achieved for a SiH4 concentration of 67% diluted in H2 with a high Raman crystallinity I c/I a > 2.5 and a low defect density of 1−2 × 1016 cm−3 by adjusting the plasma conditions. Contrary to the case of a conventional rf plasma, the defect density of the µc-Si films strongly depends on substrate temperature, T s, and increases with increasing T s even if T s is below 300 °C. This indicates that the real temperature at the growing surface is higher than the monitored value. A sufficient supply of deposition precursors such as SiH3 at the growing surface under an appropriate ion bombardment is effective for the fast deposition of highly crystallized µc-Si films as well as for the suppression of the amorphous incubation and transition interface layers at the initial growth stage.

Gas mixtures containing humid air, various proportions of CO2 and traces of NO2 are submitted to a short gap point-to-plane DC corona discharge in a reactor at atmospheric pressure. These mixtures can be considered as the basic component of most industrial effluents. Coming after an electrical study previously published, this work is centered on the physico-chemical effects of the discharge.Concentric circular alterations appearing on a copper cathode have been analyzed by XPS, showing an oxidation and acidification spread over a great part of the surface by the electric wind. The NO2 removal and corresponding by-products have been studied by UV absorption spectroscopy on gas samples after treatment, in the 200–400 nm wavelength range where NO2 abatement and O3 concentrations can be evaluated. Being partly produced in liquid phase, HNO3 which is responsible of the acidification of cathode surface, can be studied only qualitatively. A few chemical mechanisms are propounded for both bulk and surface actions of the discharge.

In this work, a low-frequency dynamic hysteresis model is proposed and applied to nonoriented Fe-Si steel. The model based on Preisach theory can be used when skin effect is negligible over the lamination thickness. In our model, the Preisach engine that usually takes the magnetic field as input variable must be inverted. Some B(H) symmetric loops are calculated and compared with measurements in the rolling direction both in quasistatic and dynamic operations under sinusoidal induction.

This paper proposes a general applicable algorithm for the optimization of the current density distribution in the electrochemical cells using the insulating shields during the electroplating process. The innovative aspect is that the position of the insulating shield is displaced over a number of predefined time steps convecting its surface proportional with and in the direction of a well chosen rate provided by a genetic algorithm. The aim of this method is to develop a systematic modification of the insulating shield position in order to get a more uniform distribution of the current density, hence a more uniform deposited layer at the cathode. As the displacement of the insulating shield is performed with the Level Set Method, the re-meshing of the computational domain with finite elements is not required anymore. Finally an example related to the optimization of the current density distribution in the vicinity of a singularity (incident angle between the electrode and insulator = 180°), using an insulating shield, will be presented.

The computation of induced currents in a conductor whose shape isa dome is achieved iteratively by dividing this conductor intoseveral elementary layers to take into account the tridimensionalbehaviour of the induced currents.

In this paper we present an investigation into the possible link between the pressure of the gas in the surrounding environment and the rate of ice sublimation in a VPSEM (variable pressure scanning electron microscope). Although this is mainly significant to an electron microscopist working in a variable pressure environment, it is relevant to people working at low pressures who wish to have control over the rate of sample dehydration where the input of water vapour is not a viable alternative.

Existing implementation of perfectly matched layers (PML) constraining the computational volume in an electromagnetic modeling of open structures has been shown to be efficient. However, cases with absorbing materials inserted into PML require substantial amount of memory and calculation time spent on the computation of the field inside the PML layer. In this paper we are addressing these problems by introducing a new computational method. As the procedure requires some substantial amount of memory and operations to compute fields in the PML layer, the paper addresses these issues. The PML split-field equations are revisited yielding a reduction from four-term storage to only three. In addition, the new algorithm is used with a new hybrid MRTD-FDTD (HMRTD) method applied to various lossy structures, conjointly with a higher-order field evaluation. Results demonstrate the efficiency of the new PML algorithm as compared to current schemes.

Surface modification was performed on the indium-tin-oxide (ITO) thin films by oxygen inductive coupling plasma (O-ICP) and oxygen plasma immersion ion implantation (O-PIII). The electronic states of ITO surfaces were characterized by X-ray photoelectron spectroscopy (XPS). The observed peak shifts of O 1s, In 3d5/2 and Sn d5/2 core levels showed that the work function of ITO can be further enhanced by O-PIII treatment, compared with that of untreated and O-ICP treated surfaces. The deconvolution of O 1s spectrum and calculation of stoichiometry showed that the work function improvement should be attributed to the increase of effective oxygen content, namely, the elimination of oxygen vacancies. In addition, the measurement of Kelvin probe confirmed that an increment of the ITO work function by 1.1 eV was obtained on O-PIII treated sample and the results sustained our proposal.

The vortex dynamics of (Y, Nd)Ba2Cu3O7−δ ((Y, Nd)123) superconductors have been studied using magnetic relaxation measurements obtained at different sweep rates. The temperature dependence of the dynamic relaxation rate (Q) is found to be not vanishing at T = 0 K, and also showed well developed maxima becoming broader and tending to move to higher temperatures with decreasing magnetic field. At temperatures close to the critical temperature (T c ), Q(T) showed well-developed minima becoming deeper and tending to move to lower temperatures with increasing field. These minima appeared to occur approximately at the same reduced temperature position [ T/T c ]as that of oxygen-controlled-melt-grown (OCMG)-Nd(123) samples, thus providing further support for pinning similarities between both systems. Both the field dependence of the characteristic pinning energy [ U c ]and relaxation rate showed significant inconsistency with the collective pinning theory but full agreement with the results of [Perkins et al., Phys. Rev. B 54, 12551 (1996)].

Cu0.62Zn0.38 foil was subjected to surface mechanical attrition treatment (SMAT) processing first. Growth behavior of ZnO nanostructure on the SMAT Cu0.62Zn0.38 surface during thermal oxidation was investigated in this paper. The original and SMAT Cu0.62Zn0.38 foils were thermally oxidized at 400 ~ 700 °C under various gaseous environments, including nitrogen and mixture of N2-O2 at a pressure of 1 atm. for 3 h. The oxidized specimens were characterized with a scanning electron microscope, an X-ray diffractometer and a transmission electron microscope. It is found that nanosheets are easily formed on the SMAT specimen surface. The favorable formation of nanosheets relates to twin lamellae structure of Cu0.62Zn0.38 formed during SMAT processing.

X-ray emission from a compact diode consisting of a sharp edged cathode and flat anode of copper and lead, energized by simple capacitor discharge is reported. With a sewing machine needle cathode, and lead target, the generation efficiency upto 0.4% is obtained. The efficiency is expected to enhance further with the increase in discharge energy, charging voltage and reducing the parasitic inductance.

The stabilized fibers with different relative cyclization index were prepared by stabilization of electrospun polyacrylonitrile (PAN) fibers at temperatures of 275, 290 and 300 ºC. Then electrospun PAN-based carbon fibers were prepared by carbonization of the stabilized fibers at 700 ºC in a nitrogen atmosphere. The thermal property of as-spun fibers during the stabilization process was investigated by differential scanning calorimetry. The evolution of chemical structure and morphology of the PAN-based stabilized fibers was studied by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. Microwave electromagnetic properties of these carbonized fibers were investigated in the range of 1.5–18.0 GHz by the vector network analyzer. The reflection loss was calculated by the measured electromagnetic parameter. The results indicate that the stabilization has a significant effect on the electromagnetic and microwave absorbing properties of the carbon fibers.

Dc conductivity measurements for Z-cut natural quartz plates, at different temperatures and values of the applied electric field were made. The evolution of I−V characteristics shapes is studied for electrodiffusion times up to 100 h (in interstitial alkali ions transport region). The non-ohmic behavior is discussed and is considered to be due to the space charge produced by the uncompensated Al3+ ions substitutional for Si4+.