Synthesized ZnO nanotubes have finite wall thickness and holy hexagon section. Using density functional theory first we calculated structural and electronic properties of isolated and bundle of these systems. Then same calculations are performed for these systems which encapsulated Fe nanochain or Fe nanowires with different thickness. We found for both cases the bundle is more stable than isolated nanotube. Both pristine of isolated and bundle are semiconductor, in which the bundle energy gap is less than isolated nanotube. All encapsulated systems are spin polarized ferromagnetic with high magnetic moment. In each encapsulated nanotube for lower thickness all ZnO layers are metal but for high thickness the outer layers remained semiconductor.

Microstrip ring resonator (MSRR) is an efficient technique for electromagnetic material characterization in microwave bands. Ferrites constitute important class of materials for microwave devices, especially for RF passive components. The aim of the work was to characterize ferrite materials using the frequency response of MSRRs. A theoretical analysis of the problem has been developed to find a relation between the ring resonance frequencies and the electromagnetic properties of ferrite such as effective permittivity and permeability. The measurements made on YIG (101) from 1 to 30 GHz are found to be in good agreement with the theoretical results. And the MSRR technique applied on ferrite materials has been validated.

TiO2 nanotubes were synthesized via electrochemical anodization of Ti foil at 60 V for 1 h in a bath with electrolytes composed of ethylene glycol containing 5 wt.% of NH4F and 1 vol.% of H2O2. The incorporation of optimum Cu2+ ions (1.30 at.%) into TiO2 nanotubes were prepared by using wet impregnation method to improve their photocatalytic methyl orange degradation and Pb(II) heavy metal removal. The small Cu2+ ions were successfully diffused into lattice of TiO2 nanotubes by conducting post-annealing treatment at 400 °C for 4 h in argon atmosphere after wet impregnation. In this manner, optimum Cu2+ ions played a crucial role in suppressing the recombination of charge carriers by forming inter-band states (mismatch of the band energies) within the lattice of Cu-TiO2. The experimental results showed that a maximum of 80% methyl orange removal and 97.3% Pb(II) heavy metal removal at pH 11 under UV irradiation for 5 h. Besides, it was noticed that photocatalytic Pb(II) heavy metal removal was strong dependence on pH of the solution because of the amphoteric character of Cu-TiO2 in an aqueous medium.

In this paper the mutual phase locking theory of very nonidentical spin-torque nanooscillators, which is based on the Slavin-Tiberkevich model, considering the theory of nonlinear oscillations, is developed. Using generalized Adler equation we calculate phase-locking region of the system with spinwave coupling in the parameter plane - distance between nanocontacts and radii difference. We describe trajectories of such a system in the phase space and show the effect of a broadband synchronization. We introduce a generalization of this approach to the ensembles of spin-torque nanooscillators.

The resolution of classical imaging is limited by the Rayleigh diffraction limit, whereas ghost imaging can overcome this diffraction limit and enhance the resolution. In this paper, we propose a super-resolution thermal ghost imaging scheme based on deconvolution, which can further improve the imaging resolution. Because the traditional thermal ghost imaging result is the convolution between the original image of the object and the correlation function, we can use deconvolution algorithm to decrease the effect of convolution and enhance the imaging resolution. Actually, the correlation function of ghost imaging system is just the point spread function (PSF) of classical imaging system. However, PSF is hard to obtain in classical imaging system, and it is easy to obtain in ghost imaging system. So deconvolution algorithm can be easily used in the ghost imaging system, and the imaging resolution can increases 2–3 times in practice.

The author reports that the spatial luminescent distribution from Cu substrate is in special sync with the Cu substrate morphology in terms of suspended formation of the deposited graphene fabricated via chemical vapor deposition. Moreover, the Raman 2D and G peak position of the graphene relatively shift to high frequency on the even Cu foil domain, showing more compressive strain than the uneven region. The author can reveal that the reducing compressive strain by virtue of the uneven Cu domains in order to minimize the interaction between graphene and Cu substrate has one of the important roles in forming suspended graphene. Current mapping in small dimension additionally shows that the current flow is mostly detected at the nano-terrace regions than the even, further substantiating the significance of the detailed underlying Cu substrate morphology. The author can also shows the correlation between the graphene strain revealed via 2D peak shift on Cu surface and the sheet resistance value of graphene on PET substrate, suggesting the degree of suspended formation of the graphene on Cu may be one of the important factors in increasing electrical performance on PET substrate.

In this work, we study the pressure-induced spin state transition in BiFeO3 by using ab initio electronic structure calculations. The applied pressure is simulated through lattice compression. The Fe ion is found to be in the high-spin (S = 5/2) state in the insulating ground state. Along with Bi6p, Feeg and O2p orbitals are also found to be important in deciding the transport behaviour of the compound. At about 38 GPa the spin state of the Fe ion changes from high-spin to low-spin (S = 1/2) accompanied by the corresponding insulator to metal transition. This pressure is found to be in fairly good agreement with that observed experimentally.

Images of vertebrates (zebrafish and zebrafish eye) have been obtained by using an X-ray phase-contrast imaging technique, namely, synchrotron-based diffraction-enhanced imaging (SY-DEI) (or analyzer based imaging) and synchrotron-based diffraction imaging in tomography mode (SY-DEI-CT). Due to the limitations of the conventional radiographic imaging in visualizing the internal complex feature of the sample, we utilized the upgraded SY-DEI and SY-DEI-CT systems to acquire the images at 20, 30 and 40 keV, to observe the enhanced contrast. SY-DEI and SY-DEI-CT techniques exploits the refraction properties, and have great potential in studies of soft biological tissues, in particular for low (Z) elements, such as, C, H, O and N, which constitutes the soft tissue. Recently, these techniques are characterized by its extraordinary image quality, with improved contrast, by imaging invertebrates. We have chosen the vertebrate sample of zebrafish (Danio rerio), a model organism widely used in developmental biology and oncology. For biological imaging, these techniques are most sensitive to enhance the contrast. For the present study, images of the sample, in planar and tomography modes offer more clarity on the contrast enhancement of anatomical features of the eye, especially the nerve bundle, swim bladder, grills and some internal organs in gut with more visibility.

Nanostructured ZnO thin films with different precursor concentrations (0.5–0.8 M) have been deposited on glass substrates by sol-gel dip coating technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-visible spectrophotometer, and m-lines spectroscopy have been employed to investigate the effect of solution concentration on structural, morphological, optical and waveguiding properties of the ZnO thin films. XRD spectra have shown that all the films are polycrystalline and exhibit the wurtzite hexagonal structure. SEM micrographs and AFM images have revealed that morphology and surface roughness of the thin films depend on sol concentration. The UV-visible transmittance results show a high transparency in the visible range and a shift of the maximum transmittance to the higher wavelength with increasing sol concentration. Waveguiding properties such as refractive index, number of propagating modes and attenuation coefficient measured at 632.8 nm wavelength by m-lines spectroscopy indicate that our ZnO slab waveguides are single mode and demonstrate optical losses estimated around 1.5 decibel per cm (dB/cm) for the thin film prepared with a sol concentration of 0.7 M.

The paper presents the measurement and computation of the corona onset voltages, electric field and ion current density profiles of a new “Tri-electrode system” intended for electrostatic separation applications. Unlike the well-known “dual cylinder-wire electrode system”, the new system utilizes an extra adjustable wire in order to provide the means for a more efficient ion charging current; necessary for separation of different granular mixtures. An experimental setup is constructed to model the present multi-electrode arrangement. The measurements are carried out for wire diameters between 0.3–1.0 μm and for different geometrical parameters. Without resorting to the commonly used Deutch’s assumption, a computational scheme is developed to solve the corona equations and to compute the associated ionized field quantities of the system. Mapping of the ion flow field patterns demonstrates the impact of this assumption on the solution’s accuracy. The computed results were found to be in good agreement with experiments. The configuration offers a more efficient charging process and separation in comparison with earlier separators’ designs.

The study is about the effect of H2 addition into N2 on the density of radiative species in the plasma and in the late afterglow of microwave flowing discharges at low gas pressure (2–10 torr). Intensities of radiative N2(B, C), N2+(B) neutral and ion molecules, H atoms and NH radicals were measured in the plasma and in the late afterglows for the N2(B) state. The results are discussed from the main kinetic reactions in the N2-H2 plasma and afterglow. From the intensity of N2, 1st pos. at 580 nm and after calibration by NO titration, the N-atom density in the afterglow can be determined. The variations of the N-atom density with H2 into N2 in the late afterglow are examined for several gas pressures (2–10 torr) at fixed microwave power (100 W) and flow rate (1 slm). The activity of the late afterglow has been measured on paper surfaces, outlining the influence of a few H2 into N2.

The mixture distributions for statistical time delay of electrical breakdown are proposed along with the generalized relation for the effective electron yield. The validity of the proposed model is tested by applying this distribution to experimental data measured in synthetic air at low pressure. Two samples without and with oxide surface are compared in order to determine physical processes leading to appearance of mixture distributions in the case of oxidized cathode. The obtained distributions are tested by Kolmogorov-Smirnov statistical hypothesis test in order to justify the use of mixture distributions. The physical interpretation of mixture distribution measured in the synthetic air is proposed, accompanied by the calculated values of the effective electron yield of initiating electrons in the gas gap.

The behaviour of DC corona discharge in air that is free of particulate matter with the wires-to-plane geometry was analysed in this work. The formulae I = KV (V − V0) and I = A (V − V0)m commonly used for the current-voltage characteristics were used to determine the various corona parameters for the two polarities of the corona discharge. Using curve fitting, it has been shown that the geometric factors K and A and the exponent m are strongly affected by the number n of the discharging wires. However, the corona inception voltage determined from the measurements is weakly influenced when n is small, and it remained constant for n > 5 discharging wires. As for the breakdown voltage of the discharge, it is practically independent of the number n. Furthermore, it was verified that the two formulae above can be used for both negative and positive corona in multiple wires-to-plane geometries.

This work deals with the characterization of DC electric arcs in aeronautical conditions of pressure (104 Pa–105 Pa). Characteristics of electric arcs such as the mean electric field in the arc column, the anode and cathode voltage drops, the length for which the arc extinguishes naturally and the mean energy dissipated per arc have been measured for three current values: 7, 70 and 300 A. The decrease of pressure leads to an increase in the arc length which can be two times longer in pressure conditions reached during a flight than in atmospheric pressure conditions. This is correlated with the variation of the mean electric field with pressure. Consequently, the energy dissipated per arc is also amplified.

This paper studies the influence of inert gas additions He, Ar, Kr and Xe on breakdown voltage within dielectric barrier discharge reactor with oxygen feed gas. The density-normalized effective ionization coefficients αeff/N are calculated for inert gas/O2 mixtures, the critical reduced field E/Ncr is obtained where the electron ionization exactly balances the attachment. Adding inert gases would lead to the decreasing critical reduced field strength E/Ncr due to the enhancement of effective ionization coefficient. In addition, inert gas additions have shown to reduce the breakdown voltage. Moreover the numerical breakdown voltage values and the experimental data are plotted for the sake of comparison and results show that calculated results are in agreement with the experimental values. Parametric study offers substantial insight in plasma physics, as well as in ozone generation applications.

The scanning of parts in eddy current testing can lead to a large amount of measurement data (predictors). Partial least square (PLS) regression is a mean to reduce the dimensionality of the subsequent inverse problem by projecting the predictors in a latent subspace of reduced dimension maximizing the covariance between the projection and the responses which have to be estimated. In a second step, a regression model is elaborated linking the responses to the latent variables. PLS was originally developed in the field of chemical analysis. In this paper, the PLS method is applied in the field of eddy current testing for the characterization of minute cracks. It is tested firstly on simulated data and then on experimental data. It is found that the reconstruction of the area of minute cracks is made possible by PLS.

This paper is aimed at an experimental investigation on effects of initial pressure on flame propagation characteristics of binary fuels hydrogen-propane-air mixtures at room temperature. The experiments are performed in a square channel equipped with perforated orifice obstacles. Four initial pressures are examined. Based on pressure transducers along the channel, the flame velocity, maximum pressure of the front peak and characteristic distances are measured. Successive stages are observed as flame propagates: (i) a velocity increase at the beginning, (ii) a velocity equal to the sound speed of combustion products and (iii) a decrease of the velocity. When the initial pressure is more important, the flame velocity and the maximal pressure of the front peak are higher, which yields a shorter characteristic distance of flame propagation. By means of a Schlieren photography technique, the physical mechanisms of flame propagation are identified in its initial stage. The physical mechanisms such as flame surface area increase and combustion product expansion as well as delayed combustion between two adjacent plates are responsible for flame acceleration upon its initial stage. The oscillations of the centerline flame velocity are due to the constrained-expanded structure of flow in reactants ahead of flame when it crosses the plates.

First principle calculations are employed scheme to investigate the electronic structures and mechanical properties of AlCu3 with divacancy defects using the pseudopotential plane wave method. The defect crystal is constructed by removing the nearest Al or Cu atoms to form the double point vacancies. Calculated lattice constants agree well with the experimental data. Moreover, structural stabilities of crystals containing divacancy are reduced. Results reveal that the crystal with double Cu vacancy defects is more stable than that of Al. Calculations of defect formation energies indicate that the divacancy of Cu is easier to exist in AlCu3. Divacancy defects play an important role to improve the mechanical properties of AlCu3 and corresponding ductility, stiffness and plasticity are increased. Furthermore, chemical bonds become weaker since the divacancy are introduced. Hybridizations between orbits of crystals are analyzed to account for the interactions in perfect and defect structures. Accordingly, implications of these findings on the mechanism of divacancy are discussed.

Numerical and experimental investigations of a broadband vibration energy harvester with triple-well are presented. The nonlinear restoring force of the tristable oscillator is experimentally identified as a high order polynomial that depends on the relative spacing and locations of the magnets in the magnetically coupled piezoelectric cantilever. Simulations and experiments are performed at different harmonic excitation levels ranging from 10 to 35 Hz. The tristable energy harvester possesses the unique jump characteristics of oscillation center stemming from excitation level and initial displacements. Its broad frequency range of 15.1–32.5 Hz is obtained from the transition among three wells. It is also demonstrated that the tristable nonlinear oscillator will be more helpful to improve the broadband performance for harvesting vibration energy under low frequency excitations.

For a solution droplet in equilibrium with the atmospheric environment, a relationship exists between radius and concentration, which allows to express the saturation ratio of the droplet as a function of either one of these two parameters. The curves showing the complete behaviour of saturation ratio as a function of radius, for various sizes of NaCl nuclei, were previously presented for both wholly and partially dissolved salt. Here, the dependence of saturation ratio on droplet concentration, rather than on its radius, is examined and plotted for various NaCl nuclei. The occurrence of an analogous, but X-shaped, hysteresis phenomenon, characterizing the behaviour of the solution concentration in a growing-shrinking cycle of a solution droplet under changing humidity, is evidenced and discussed. An insoluble spherical core is assumed to be always present inside the condensation nucleus, so that the onset of the sudden salt re-crystallization is triggered at a well defined concentration value.