The influence of precursor medium was investigated on the structural, morphological, optical and electrical properties of spray pyrolysis deposited nanostructured ZnO thin films. Three batches of ZnO thin films were deposited on glass substrates using three different solvents (water, water-ethanol [ratio of 1:1] and ethanol) based precursor solution of zinc nitrate hexahydrate. The substrate temperature was fixed at 523 K. The variation in film thickness from 150 to 875 nm was observed as the effect of changing solvent medium. X-ray diffraction (XRD) data confirmed the formation of polycrystalline ZnO thin films with hexagonal wurtzite crystallite structure and the estimated crystallite size was found to be ranging from 31 to 55 nm. Scanning electron micrographs revealed the formation of water-hyacinth shaped nanostructures when water-ethanol mixture was used as the solvent medium. Interestingly, UV-vis spectrophotometer revealed the formation of ZnO film with twin optical band gap of 3.15 eV and 3.56 eV when ethanol was used as the solvent medium. The modulation of film thickness and grain size by solvent medium has strongly influenced the electrical conductivity of ZnO thin films. The homogenous nano-spherical grains with uniform grain boundaries showed a good response towards 100 ppm of ammonia at room temperature.

The effect of electron beam irradiation of stoichiometric hydroxyapatite (Ca10(PO4)6(OH)2, HAP) is investigated using electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) mode equipped with a LaB6 gun. Initial irradiation at 160 A cm−2 dose rate shows no modification of the low loss spectra. No difference of mass loss for Ca, O and P is observed for two different probe diameters: 4 nm (dose rate = 160 A cm−2) and 24 nm (dose rate = 70 A cm−2). Furthermore no formation of CaO is observed for both experimental conditions. It is proposed that the low values of both electron dose rates and doses (from 350 to 2400 C cm−2) avoid mass loss. At the higher dose rate obtained with a field emission gun (FEG), transformations are observed for the lowloss signal as well as for the Ca, P and O signals. These results might be very useful for the future studies of apatite particles at the nanoscale.

In the present work, we have studied the effect of impurity position on energy levels, the donor binding energy and third harmonic generation of a pyramid and a cone like quantum dot. For this goal, we have calculated the energy levels, wave functions and binding energy using finite element method for various impurity positions. Our results show that the impurity location plays an important and considerable role in the electronic and optical properties in a pyramid and a cone like quantum dot. We found that the third harmonic generation and binding energy of both quantum dots have a maximum value at a special impurity position. The special impurity location is different for the two quantum dots. Also, we have deduced that the third harmonic generation of a cone like quantum dot is larger than a pyramid quantum dot for same volumes and heights.

Using the first-principles calculations based on the spin-polarized density functional theory (DFT), we investigated the structural, electronic and magnetic properties of Cu-doped single walled ZnO nanotubes (SWZnONTs). Our results show that for a unit cell with 40 Zn and 40 O atoms, substitution of a single Zn atom by a Cu leads from a semiconductor to a ferromagnetic (FM) half-metallic phase transition with 100% spin polarization. In this case the total magnetic moment of super cell is 1.0 μB. To investigate the effects of Cu-codpoed SWZnONTs two different configurations are considered, first we assumed the two Zn atoms replaced by two Cu atoms are close and second they are far from each other. When Cu atoms are at the nearest-neighboring positions, the antiferromagnetism (AFM) phase is stable, while increasing the distance between the two Cu atoms, the ferromagnetism stability increases. In the AFM phase the structures are nonmagnetic semiconductors, but in the FM phase all these systems are half-metallic systems with 100% spin polarization, so it can be used as magnetic nanostructure and future applications in permanent magnetism, magnetic recording, and spintronics.

Pb1-xSnxS nanopowder with different Sn concentrations (x = 0.02, 0.05, 0.10, 0.20, 0.50 and 1.00) were synthesized by chemical precipitation route under N2 atmosphere. The samples were characterized by X-ray diffraction(XRD), UV-vis absorption spectra and photoluminescence (PL) spectra. The XRD results show that the samples with 0 ≤ x ≤ 0.2 have cubic (fcc) structure with diameter in the 12.8–24 nm range. The sample with x = 0.5 has orthorhombic structure with a diameter of 9.2 nm. The band gap (or absorption edge) of PbS exhibits a large blue shift when the crystallite size is reduced to nanometer scale, from 0.4 eV in bulk samples to 1.8 eV in nanosize samples, which can be related to large Bohr excitonic radius of PbS nanoparticles. PL emission spectra of Pb1-xSnxS in red region excited at 315 nm, for x = 0 showed three broad peaks located at 776.5 nm, 809 nm and 826 nm which due to the defect densities and for x = 0.02, 0.05, 0.10 there are two relatively strong emission peaks located at 786 nm and 823 nm which can be related to transition from sulfur vacancy level and Sn+2 ion level respectively.

In order to improve the utilisation and performance of anode catalysts in direct methanol fuel cells (DMFCs), functionalised multi-walled carbon nanotubes (MWCNTs) are used as a support for palladium (Pd) nanoparticles synthesised by photochemical reduction. MWCNTs are modified by methylene blue (MB) under ultraviolet light (fuv-MWCNTs), and then Pd nanoparticles are assembled on the fuv-MWCNTs to form composites (Pd/fuv-MWCNTs). The method is green, simple and does not destroy the pristine structure of the MWCNTs. The morphology and structure of prepared composites are characterised by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that Pd nanoparticles with face-centred cubic crystal structure are about 3.9 nm in size, and are uniformly dispersed on the surface of fuv-MWCNTs. X-ray photoelectron spectroscopy (XPS) reveals that N-containing and S-containing groups exist in fuv-MWCNTs. These groups might be active sites for assembly of Pd nanoparticles on the surface of fuv-MWCNTs, and can modify the electronic structure of Pd nanoparticles. Electrochemical experiments indicate that the prepared Pd/fuv-MWCNTs catalyst exhibits excellent catalytic performance. The catalytic activity of Pd/fuv-MWCNTs is 1.94 times higher than that of commercial Pd/C for methanol oxidation in alkaline solution. It indicates that UV irradiation can facilitate MB to functionalise MWCNTs, reinforce the modification of the electronic structure of Pd, and enhance the catalytic activity of Pd/fuv-MWCNTs.

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.

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.

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.

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.

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 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.

A self-decoupled inelastic style piezoelectric three-degrees-of-freedom (three-DOF) accelerometer is put forward for the solution of cross coupling interference without decoupling easily in the field of three-DOF acceleration sensing. Meanwhile, the proposed piezoelectric three-DOF accelerometer has simple structure and solves the contradictions between high stiffness and high sensitivity. The operating principle of the presented piezoelectric three-DOF accelerometer is analyzed, and its structure model is constructed. The numerical simulation model (finite element model) of the three-axis accelerometer is established. Piezoelectric quartz is chosen for the acceleration sensing element and conversion element, and its output sensitivity, static characteristics, dynamic natural frequency, etc. are analyzed by FEM tool (ANSYS software). Research results show that the proposed piezoelectric three-DOF accelerometer has advantages of simple and rational structure, correct sensing principle and mathematic model, good linearity, high rigidity, and theoretical natural frequency is more than 16 kHz, self-decoupled without complex decoupling work.

Self-consistent ab initio calculations, based on the density functional theory (DFT) approach and using the full potential linear augmented plane wave (FLAPW) method, are performed to investigate both the electronic and magnetic properties of CrSb compounds. Spin-polarised calculations, including the spin-orbit interaction, are used to determine the energy of the ferromagnetic (FM) and antiferromagnetic (AFM) states of CrSb. Magnetic moments considered along the (0 0 1) axis are computed. Data obtained from ab initio calculations are used as input for high temperature series expansions (HTSEs) to compute other magnetic parameters. The exchange interactions between the magnetic atoms Cr-Cr in CrSb are studied using the mean field theory. The high temperature series expansions (HTSEs) of the magnetic susceptibility are given up to tenth order (x = J1(Cr-Cr)/kBT). The Néel temperature TN is obtained by HTSEs of the magnetic susceptibility combined with the Padé approximant method. The critical exponent γ associated with the magnetic susceptibility is deducedas well.

Previous researchers have made studies on different influences created by light irradiation to animals, including retinal damage, changes of inner index and so on. However, the model of light induced damage to animals using physiological indicators as features in machine learning method is never founded. This study was designed to evaluate the changes in micro vascular diameter, the serum absorption spectrum and the blood flow influenced by light irradiation of different wavelengths, powers and exposure time with support vector machine (SVM). The micro images of the mice auricle were recorded and the vessel diameters were calculated by computer program. The serum absorption spectrums were analyzed. The result shows that training sample rate 20% and 50% have almost the same correct recognition rate. Better performance and accuracy was achieved by third-order polynomial kernel SVM quadratic optimization method and it worked suitably for predicting the light induced damage to organisms.

It is well-known that the characteristics of aluminum nitride thin films mainly depend on their morphologies, the quality of the film-substrate interfaces and the open volume defects. A study of the depth profiling and morphological characterization of AlN thin films deposited on two types of Si substrates is presented. Thin films of thicknesses between 200 and 400 nm were deposited during two deposition times using a reactive sputter magnetron. These films were characterized by means of X-ray diffraction and imaging techniques (SEM and TEM). To analyze the composition of the films, energy dispersive X-ray spectroscopy was applied. Positron annihilation spectroscopy, specifically Doppler broadening spectroscopy, was used to gather information on the depth profiling of open volume defects inside the films and the AlN films-Si substrate interfaces. The results are interpreted in terms of the structural changes induced in the films as a consequence of changes in the deposition time (i.e., thicknesses) and of the orientation of the substrates.