Coherent phonon scattering and transmission via a three-terminal junction in low-dimensional structures is investigated. The model system consists of two-dimensional crystalline wave-guides, constructed of double atomic chains that are joined together by a nanostructured T-shaped junction. The matching method theoretical approach is used to study the dynamics of the system. A calculation is presented for the coherent reflection and transmission scattering probabilities of the system phonons, as elements of a Landauer type scattering matrix. The scattering and transmission spectra via the T-shaped junction are analyzed as a function of the incident frequency per propagating mode of the perfect wave-guides. Our results show that the junction is an effective phonon splitter and suggest that its characteristics may be controlled by varying its nanometric parameters. Asymmetric Fano-like resonances are observed in the spectra which result from the coherent coupling between the localized modes of the T-shaped junction and the propagating modes of the wave-guides.

A method of heat-assisted magnetic recording (HAMR) is characterized. The recording medium is a high coercitivity, granular and perpendicular CoNi/Pt multilayered film. Emission current from a scanning tunneling microscope (STM) is the heating source. Experiments show that an average mark size of 90–120 nm is achieved. A model for achieving 1 terabit/sq.in. recording density (or a mark size of 25 nm) is proposed to guide future effort.

The relaxor ferroelectric ceramics of La doped xPb(Mg1/3Nb2/3)O3-(1 − x)Pb(Zr0.55Ti0.45)O3 are synthesized by columbite precursor method. Powder X-ray diffraction patterns of these compositions indicate pseudocubic phase formation. Grain growth is inhibited with La doping and is increased with PMN concentration in PMN-PZT ceramics. $\varepsilon_{RT}$ and tan δ are increased to 1.5 mole% La doped PMN-PZT compositions while $\varepsilon_{T_C}$ and TC are decreased with La modification in PMN-PZT system. Pure and La modified 0.8PMN-0.2PZT compositions have shown the most promising relaxor behavior useful for multilayer capacitor (MLC) applications. The ferroelectric properties (Ec, Pr and Ps) are increased to 1.5 mole% La doped PMN-PZT composition. 77.84.Dy Niobates, titanates, tantalates, PZT ceramics, etc.

Basing on finite-difference time-domain method and partial band gap effect of photonic crystal, we obtain collimated light beams from point optical source and two-dimensional photonic crystal structure. The diffusive light with some special frequencies can be collimated and propagate along a special direction within photonic crystal structure. Our study presents a new method to make light collimator.

Interconnected microstructural ZnO:Al thin films with low doping concentration (Al/Zn ≤1%) were deposited on (0001) sapphire substrates by the sol-gel technique. The effects of low doping concentration on the structural, optical and electrical properties of the films were investigated. Scanning electron microscope (SEM), X-ray diffraction (XRD), photoluminescence (PL), and four-point probe method were used to characterize the structural, optical and electrical properties. We found that with increasing the dopant concentration the interconnected thread becomes thinner, the (002) diffraction peak and the near band edge (NBE) emission are enhanced while the deep level emission (DLE) and the resistivity are decreased.

We have studied the characteristics of a plasma reactor for the promotion of chemical reactions aimed to hydrogen reforming from gaseous hydrocarbons. A plasma torch-like electrode configuration was powered by a limited current, high voltage DC source. Using as process gas an argon/methane mixture at atmospheric pressure, we have produced an intermittent spark discharge which has been investigated at different operating parameters. Experimental information on the discharge have been used to perform a numerical simulation of the plasma chemical kinetics. The evolution of the gas-phase composition during and after the interaction in the discharge region was calculated under different operating conditions. The results have been used to predict the hydrogen production yield in the experiments and to study the role played by the different discharge parameters in order to determine the optimal interaction between plasma and gas mixture.

In order to save the computing time of Monte Carlo simulation, traditional null collision method is improved in which only one cross section needs to be evaluated at each collision speed. By this method, the electron swarm parameters such as effective ionization coefficient, $\bar{\alpha}$, drift velocity and diffusion coefficient of SF6 and CF4 gas mixtures are calculated over the E/N range from 150 Td to 500 Td. A set of electron collision cross-sections that gives transport parameters in agreement with measurements for the pure gases is used. The simulation results are then compared with our experiment data, and show excellent agreements.

This paper presents an uncertainty budget of measurement on the optical phase on the basis of a metrological analysis inspired from the “GUM” approach [GUM, Guide to the expression of Uncertainty in Measurement (ISBN 92-67-20188-9, 1993)]. This budget takes account of the procedure implemented in calibrating the phase-shifting device and in the actual phase measurement. This study leads to deriving an estimation of the standard uncertainty in measuring the optical path difference at approximately $\lambda/98$. This value agrees with a purely experimental estimate [F. Taillade, Association de la shearographie et des ondes de Lamb pour la détection rapide et quantitative des délaminages, Ph.D. thesis, Technical Note ONERA, NT 2001-3, 2001], which led to a standard uncertainty of roughly $\lambda/108$.

Magnetostatic forces computation can be done numerically through Finite Element Analysis by applying the virtual works method on either the energy or the co-energy. They can also be computed analytically using Maxwell's tensor. Different results have been obtained using these two procedures. In this work we will introduce a general way of obtaining magnetostatic stress tensors (Maxwell's tensors) from either the energy or the co-energy. Both tensors are equivalent in induced magnetisation media (media whose magnetisation depends on an external magnetic field), but they are different in permanent magnets (media whose magnetisation does not depend on an external magnetic field). In these media, normal components of the surface forces derived from either the energy or the co-energy are the same, but tangential components have different modules, keeping the same direction as the tangential components of magnetic field H or magnetic induction B respectively. Force density is also different. Forces computed from co-energy do not have the same conservative characteristic as forces computed from energy. The application of Maxwell tensors in the calculation of forces over the real surface of magnetic media must take into account the discontinuity of the forces from one medium (particularly a vacuum) to another. Generally, normal stresses in all media, obtained from the energy and the co-energy, are discontinuous, while tangential stresses are only discontinuous in processes derived from the co-energy in permanent magnets.

Room temperature Mössbauer, X-ray and IR spectral studies were carried out for the spinel system Mn0.5Zn0.5AlxFe$_{2-x}$O4, $0 \le x \le 1$, prepared using the usual ceramic technique. X-ray patterns confirm that all samples have single phase cubic spinel structure. The Mössbauer spectra of the samples show a six-line magnetic pattern and a central paramagnetic phase. They are assigned to two magnetic subpatterns and two quadrupole doublets due to Fe3+ ions at the tetrahedral A-sites and octahedral B-sites. The effect of increasing the Al3+ content x on the hyperfine interaction parameters is studied and discussed. The lattice constant, oxygen positional parameter, mean ionic radius of the A- and B-sites, bond lengths, edges and interionic distance are affected by the additional process x. They are determined and discussed as functions of x. The IR spectra shows six absorption bands in the range 222–1033 cm−1. The bands are attributed to the corresponding metal-oxygen complexes in the A- and B-sites. The hyperfine interaction parameters, the IR band positions and intensities reveal their dependence on the Fe3+−O2− bond length and the interionic distance at A- and B-sites. The variation of the quadrupole doublet splitting for the B-site and the oxygen parameter reveal the increasing trigonal distortion of the B-site oxygen coordination. The IR absorption at 222 cm−1, the velocity of the infrared waves when passed through the samples and the jump rate of the lattice vacancies were found to decrease.

The explicit incompressible algebraic Reynolds stress model proposed by Gatski and Speziale [J. Fluid Mech. 254, 59 (1993)] has been extended to be applied to compressible turbulent flows. This extension is based on the modeled compressible transport equations for the Favre-averaged Reynolds stress tensor. The resulting model is tested in a variety of compressible turbulent flows which include the homogeneous shear flow and the compressible mixing layer. Comparisons between the present model predictions and the results of direct numerical simulations and experiments are quite encouraging.

The correlated photons source is obtained from the parametric down conversion of photons generated in a non linear crystal. When associated with a system of coincidences counting, this source allows one to measure the detection efficiencies of detectors working at photon counting levels, without the need for reference sources or detectors. At the Institut National de Métrologie (France), this method was implemented with the aim of realising a new standard detector for the absolute measurement of very weak radiations. The relative standard uncertainty of the detection efficiency measurements is 1.1%.

This study was undertaken to investigate whether low frequency magnetic fields can affect the characteristic of cancer cells. To achieve this, HL-60 cells were exposed to 20 mT, 50 Hz sinusoidal magnetic field and the cell viability, cell cycle phase distribution, DNA ladder and apoptotic morphology between control and exposed cells were examined. The results demonstrated that magnetic field had pronounced inhibition effects on cell growth, and small but significant changes in cell cycle phase can be observed. Internucleosomal DNA fragmentation and morphological changes after exposure indicate that the magnetic field induces apoptosis in HL-60 cells. The results also indicate that the growth-inhibitory property of MF on HL-60 cell growth was mainly due to the induction of apoptosis.