The aim of this article is to explore materials made of polymer-titanate composites for application towards the size reduction of high frequency electronic components. A study has therefore been done on the dielectric effect of composites made of an epoxy matrix loaded with a mixture of barium titanate and calcium titanate. The effects have been quantified according to volume fraction of load. Results obtained from time domain reflectometry have been compared to modelling predictions from the generalized Lichtenecker law. Low frequency analysis (in the range DC — 500 MHz) has also been performed throughout this work, and it has primarily concentrated on conductivity behaviour which may be attributed to the effects of a percolation process. The study has confirmed the validity of the ternary mixture law being applied in order to predict the electromagnetic behaviour of the composite material. This material family may therefore find use in microelectronic applications and in the miniaturization of circuit components (substrates, components, cavities, antennas, etc.).

In this study, the emission spectra of OH (A2Σ → X2Π, 0-0) and N2 (C3Πu → B3Πg) emitted from the high-voltage DC (direct-current) corona discharge of N2 and H2O mixture gas in a needle-plate reactor are successfully recorded at one atmosphere. The relative vibrational populations and the vibrational temperature of N2 (C, v') in negative DC corona discharge are determined. The effects of discharge voltage, input power and added oxygen on the relative populations of OH (A2Σ) radicals and N2 (C3Πu) molecules in negative DC corona discharge are investigated. It is found that the relative populations of OH (A2Σ) radicals and N2 (C3Πu) molecules increase with increasing the discharge voltage and the input power and decrease with increasing the added oxygen. The emission spectra produced by positive DC corona discharge are also studied for comparing with negative DC corona discharge. However, the emission spectrum of OH (A2Σ → X2Π, 0-0) is not obtained in positive DC corona discharge, only the emission spectrum of N2 (C3Πu →B3Πg) is observed. The effects of discharge voltage and input power on the relative populations of N2 (C3Πu) molecules in positive DC corona discharge are also investigated. The relative populations of N2 (C3Πu) molecules increase with increasing the discharge voltage and the input power. The main involved physicochemical processes have been discussed.

A method of dispersing nanogranules in a polymer by utilizing the stretching, compression, and shearing effects induced by bubble inflation in a polymer melt undergoing foaming is discussed. The bubble inflation is so fast, similar to the explosion of dynamite, that a complex composite stress field is exerted on the polymer melt around the inflating bubble. An expected dispersion effect of nanogranules in a polymer melt by bubble inflation has been shown by experiments. And a model, which we call In Situ Bubble Stretching (ISBS), is proposed. Comparison of a theoretical analysis of the dispersion effect is given by the ISBS method with the results from experimental scanning electron microscope micrographs given reasonable grounds for support of our hypothesis.

This article presents a group-theoretical investigation of an incommensurate magnetic structure in the case where the crystal structure is centrosymmetric while the structure vector k is not conserved by inversion. A first method starts with the conventional group-theoretical treatment taking into account the transformations which conserve kand then combines the solutions to obtain a centrosymmetric and real magnetization. A second method includes inversion in the group-theoretical treatment, for instance by introducing the complex conjugation operator and corepresentations. The general theory is applied to CeAl2 with the scope of improving the knowledge of its magnetic structure.

A cylindrical hollow cathode discharge is modelled bythe solution of the Boltzmann equation and by particle-fluid(hybrid) simulation.While the latter technique provides a self-consistent solution for the problem, the Boltzmann methodprovides detailed information about the electron kinetics in thedischarge over the whole energy range.The results obtained from the two methods areconsistent with each other and show a fair agreement with previousexperimental data thereby validating the modelling methods used.

We have investigated the existence of any possible pair breaking mechanism in Cu0.5Tl0.5Ba2Ca2Cu0.35Zn2.65O10−δ superconductor by carrying out post-annealing experiments in nitrogen, oxygen and air atmospheres. This material is grown in tetragonal structure with a and c-axes lengths 3.879 Å and 14.581 Å; the c-axis length is found to decrease with the increased concentration of Zn in the final compound. The substitution of Zn at CuO2 planar sites in formula unit Cu0.5Tl0.5Ba2Ca2Cu3−y Zny O10−δ has given superconductivity for all the Zn doping concentration of y = 0.75, 1.5, 2.25, 2.5, 2.65. The zero resistivity critical temperature [T c (R = 0)], the quantity of diamagnetism and critical current [I c (H = 0)]are found to increase with increased Zn doping. In Zn doped samples, post-annealing in air has given a maximum increase in superconducting properties, which showed that final material is optimally doped with carriers in ZnO2 planes. Since the superconducting properties are marginally suppressed in Zn doped samples by post annealing in O2 and N2 atmospheres, it has lead to a definite conclusion that pair breaking mechanism, suggested in previous studies, are absent altogether in our Cu0.5Tl0.5Ba2Ca2Cu0.35Zn2.65O10−δ superconductor. The synthesis of Cu0.5Tl0.5Ba2Ca2Zn3O10−δ superconductor by this method is extremely reproducible.

GaN nanowires were successfully synthesized on Si(111) substrates by ammoniating the Ga2O3/ZnO films at 900 °C. The structure, morphology and optical property of the as-prepared GaN nanowires were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emission transmission electron microscope (FETEM), Fourier transform infrared spectrum (FTIR) and fluorescence spectrophotometer. The results show that the GaN nanowires have a hexagonal wurtzite structure with lengths of about several micrometers and diameters ranging from 30 nm to 120 nm. The representative photoluminescence spectrum at room temperature exhibited a strong emission peak at 374.1 nm and two weak emission peaks at 437.4 nm and 473.3 nm. Finally, the growth mechanism is also briefly discussed.

Mechanical Q-factor measurements of single crystalline calcium fluoride CaF2 bulk material are presented. Resonant modes between 27 and 100 kHz were investigated on a cylindrical test sample ( $\varnothing$ $75~{\rm mm} \times 75~{\rm mm}$ ). For selected modes low temperature measurements of the mechanical Q-factor were done within a temperature range from 5 to 300 K. For the Q-measurements a ring-down technique was used. The substrate was suspended as a pendulum by means of a tungsten wire loop. The highest Q-factor has been achieved around 60 K with 3 × 108 which is the highest Q-factor reported on CaF2 up to now.

The influence of preparation conditions on the structure and optical properties of cadmium sulphide (CdS) thin films deposited on quartz substrates by means of the pulsed laser technique have been investigated. Oriented growth of hexagonal CdS nanoparticulate film with the C-axis perpendicular to the plane of the surface has been achieved up to a film thickness of 220 nm. The results indicate that the heat treatment played an important role on both crystal structure and optical properties. The grain size and the crystallinity of the films were increased, as well as the optical energy gap $E_{\it g}^{\it opt} $ (allowed direct transitions) was increased from 2.45 to 2.50 eV upon annealing. The dispersion of the refractive index of virgin and annealed films were estimated and explained using the Wemple-Didomenico (WD) single-oscillator model. The dispersion parameters and the free charge carrier concentrations were also estimated.

An exact two-dimensional (2-D) analytical model (AM) of slotless permanent magnet (PM) machines in polar coordinates is used to determine the analytical equations of the air-gap flux density at no-load operation. The authors show that, for a radial magnetization, there is an optimal magnet thickness which permits to maximize the no-load flux density. In order to use easily and directly this optimal value during the design of surface mounted PM motors (SMPMM), the authors propose an original analytical expression of this maximum magnet thickness that have been obtained by interpolation of the values given by several analytical computations. This interpolation function could be applied to SMPMM having a parallel or radial magnetization direction.

Microstructural and magnetic properties of 14N+ irradiated Co/Pd multilayers, deposited on ultra-flat large (2.5 in) glass substrates by a special hard disk industrial manufacturing system, are discussed. Upon irradiation with 14N+ ions at different energies (20–30 keV) and doses (1014–1015 ions/cm2), both the coercive and nucleation fields were found to change with respect to as deposited multilayer. Results indicate that the irradiation process leads to a lowering of the magnetic anisotropy due to the induced disorder and degradation of the interface quality: for an energy of 30 keV, at an irradiation level of 1015 ions/cm2, H c reduces from H c ≈ 5.4 kOe for the as deposited multilayer down to 300 Oe, being the easy axis still perpendicular to the multilayer plane; at the highest dose (1016 ions/cm2), the coercivity vanishes and the perpendicular anisotropy is suppressed.

This paper presents the application of the Finite Element Method FEM to the resolution of system Helmholtz coupled equations that has been obtained in the coaxial waveguides containing magnetic anisotropic materials with loss. This application is based on variational method which necessitates the construction of functional stationary written in the form of integral equation and dependent on the electromagnetic fields. After being minimized, this functional leads to algebraic equation system to which we can apply many numerical resolution algorithms. The electromagnetic study of the waveguide led us to a system of Helmholtz coupled equations which is difficult to be solved analytically. Our software code allows us to determine the electromagnetic field distribution in all points of the coaxial waveguide. The result has been validated when the coaxial waveguide was entirely loaded with air. This software has later been applied when the waveguide was partially filled with a magnetic anisotropic material with loss ( $\varepsilon_r$ ,  $\overline{\overline{\mu_r}}$ ).

We measure by fluorescence emission and absorption spectroscopy rotational and vibrational temperature of YO molecule issuing from a liquid drop of Y2O3 melted at the focus of a solar furnace. Far from the surface and at high pressure these measurements are consistent with the predictions from a fluid dynamic calculation and are believed to give an approximate temperature of the gas phase surrounding the sample. Close to the surface and at low pressure these measurements disagree with the expected surface temperature. This results from the existence of a Knudsen layer near the vaporizing surface that, in these conditions and at our spatial resolution, we can explore, revealing according the gas pressure, quasi equilibrium or non-equilibrium conditions.

The short-term stability of passive atomic frequency standards, especially in pulsed operation, is often limited by local oscillator noise via intermodulation effects. We present an experimental demonstration of the intermodulation effect on the frequency stability of acontinuous atomic fountain clock where, under normal operating conditions, it is usually too small to observe. To achieve this, we deliberately degrade the phase stability of the microwavefield interrogating the clock transition. We measure the frequency stability of the locked, commercial-grade local oscillator, for two modulation schemes of the microwave field: square-wave phase modulation and square-wave frequency modulation. We observe a degradation of the stabilitywhose dependence with the modulation frequency reproduces the theoretical predictions for the intermodulation effect. In particular no observable degradation occurs when this frequency equals the Ramsey linewidth. Additionally we show that, without added phase noise, the frequencyinstability presently equal to 2×10-13 at 1 s, is limited by atomic shot-noise and therefore could be reduced were the atomic flux increased.

Coating of Ti-6Al-4V alloy substrates with TiN/Ti multi-layered films by magnetron sputtering in Ar gas atmosphere was examined, aiming at the application of the alloy to artificial heart valves, in order to improve not only the adhesion between the deposited film and the alloy but also the surface smoothness of titanium nitride coatings and thereby to improve the blood compatibility as well as the biocompatibility of the alloy coated with the titanium nitride film. The effects of the thickness of the TiN (titanium nitride) layer on the surface morphology of the film were investigated, in order to develop TiN coatings with higher blood compatibility. The multi-layered films were deposited by sputtering in sequence pure titanium and titanium nitride targets. The thickness of titanium nitride layer was varied from 300 nm to 800 nm, while that of pure titanium was constantly 200 nm. Under visual observation, the obtained multi-layered films looked yellow gold and appeared to be uniform and adhesive, while TiN monolithic films deposited directly onto the alloy substrate under the same sputtering conditions peeled off partly. Therefore it was found that the multi-layered thin films were more adhesive to the alloy than the monolithic films. According to AFM (Atomic Force Microscope) images for both of the films, the surface morphology of each TiN layer observed under the scope of nanometer-scaled area was rough with pits and bumps, while that under the scope of micrometer-scaled area was smooth without such pits and bumps. Furthermore based on the AFM, the surface roughness $\sigma_{\it RMS}$ measured under the area of nanometer scale was found to increase with the increase of the thickness of the TiN layer in the multi-layered film, although that measured under the area of micrometer scale was assumed to be independent of the thickness of the TiN layer.

This paper presents a method of heat-assisted magnetic probe recording, which could help increase the storage density in hard-disk data storage systems. The heating source is the field emission current from a scanning tunneling microscope (STM) tip. As perpendicular magnetic recording media, two types of CoNi/Pt multilayered films are used: one is strongly-coupled and the other is weakly-coupled granular medium. Recording marks were formed by local heating in the medium. The average mark size is 180 nm for the strongly-coupled medium, and 110 nm for the weakly-coupled one. Marks are arrayed in different formations with various spacings. With reduced spacing, the write probability of the recording system is reduced. The interaction between marks becomes stronger and in the strongly-coupled medium their position becomes disordered. By contrast, this does not happen for marks written in the granular medium. Based on this demonstration, we conclude that granular medium becomes a better candidate for ultra-high density recording.

The phenomena resulting from interaction between ion beam and mammalian cell pose important problems for biological applications. Classic Bethe-Bloch theory utilizing attached V79 mammalian cell has been conducted in order to establish the stopping powers of the mammalian cell for several-MeV single-proton microbeam. Based on the biological structure of the mammalian cell, a physical model is proposed which presumes that the attached cell is simple MWM model. According to this model and Monte Carlo simulation, we studied the energy deposition and its ratio on the selected attached mammalian cell for MeV proton implantation.

A characterisation of a low pressure SF6 discharge was undertaken, by means of plasma diagnostics, including radiofrequency electrical probes, Langmuir probes and optical emission spectroscopy. Chemical kinetics modeling of the discharge was performed too. This was aimed to the understanding of a reported transition in the plasma induced surface modification on poly(ethylene terephthalate) (PET) fibres by SF6 plasma treatment which can be characterized as a striking wettability modification reverse displayed by plasma treated fibres as the SF6 pressure in the discharge exceeds a threshold value. Here we have investigated the modification also on different polymeric surface such as that of a PET film and of cellulose (paper). We point out that the observed transition could be understood as a switch between an increased surface hydrophilicity, induced by plasma treatment at low pressure, which produces also surface etching and activation, and an increased surface hydrophobicity, imparted by plasma treatment at higher pressures, due to extended surface fluorination.

In this paper the breakdown time delay t d in neon was measured and the formative time delay t f determined in three different ways: (1) from the Laue diagrams, by taking the valueswhere linear approximation of experimental data intersects the time axis; (2) from histograms, by taking the minimum values of delay times $t_{d\min}$ for the formative time; and(3) from a difference $t_f= \overline {t_d}- \overline {t_s}\approx \overline {t_d} - \sigma\,(t_d)$ , where standard deviation $\sigma\,(t_d)$ is approximately equal to the mean ofthe statistical time delay $\overline {t_s}$ . The dependency of the formative time delay on working voltages U w was found and fitted by different approximate analytical models. The separationof the formative and statistical time delay distributions was discussed and the distribution of the formative time delay experimentally obtained. The nonstationary exponentialdistributions with time dependent parameters were introduced to describe the statistical time delay distributions under conditions of increased cathode sputtering.

Perfluorocyclobutane (c-C4F8) is one of the most promising gases to be used in gas mixtures, which are the candidates to substitute for SF6 gas as high dielectric strength insulators with a reduced potential for global warming. The set of initial collision cross-sections are assembled and modified. The motion of electrons in c-C4F8 in uniform electric fields is simulated using Monte Carlo method. Also the density-normalized ionization coefficients α/N, attachment coefficients η/N, the effective ionization coefficients (α – η)/N, drift velocity (V e ) and the electron longitudinal diffusion coefficient (ND L ) are calculated for the range of density-reduced electric field strength, 300 $\leqslant$ E/N $\leqslant$ 1000 Td. The electron swarm parameters of simulation are compared with experimental data and other results of simulation, which obtain a good agreement. However, further calculations and measurements for c-C4F8, such as η/N and ND L are required.