Image simulation of high resolution energy filtered TEM images

Inelastic image simulation software is presented, implementing the double channeling approximation which takes into account the combination of multiple elastic and single inelastic scattering in a crystal. The approach is described with a density matrix formalism. Two applications in high resolution energy filtered (EFTEM) transmission electron microscopy (TEM) images are presented: thickness-defocus maps for _SrTiO3${\mathrm{SrTiO}}_3$ and exit plane intensities for an (_LaAlO3)3(_SrTiO3)3$({\mathrm{LaAlO}}_3{)}_3({\mathrm{SrTiO}}_3{)}_3$ multilayer system. Both systems show a severe breakdown in direct interpretability which becomes worse for higher acceleration voltages, thicker samples and lower excitation edge energies. Since this effect already occurs in the exit plane intensity, it is a fundamental limit and image simulations in EFTEM are indispensable just as they are indispensable for elastic high resolution TEM images.     

Exchange of angular momentum in EMCD experiments

In energy loss magnetic chiral dichroism (EMCD) experiments a chiral electronic transition is induced that obeys the dipole selection rule for the magnetic quantum number Δm=±1$\mathrm{\Delta }m=\pm 1$ or Δ_Lz=±?$\mathrm{\Delta }{L}_z=\pm ?$. The incident plane electron wave is inelastically scattered and is detected in the diffraction plane, i.e. again in a plane wave state. Naïve reasoning suggests that the angular momentum _Lz$L_z$ of the probe electron has not changed in the interaction since plane waves have 〈_Lz〉=0$〈L_z〉=0$. This leads to the seeming contradiction that angular momentum is not conserved in the interaction. A closer inspection shows that the density matrix of the probe has indeed 〈_Lz〉=±?$〈L_z〉=\pm ?$ after a chiral interaction. However, 〈_Lz〉$〈L_z〉$ is not conserved when the probe electron propagates further to the exit surface of the specimen because the rigid lattice breaks rotational symmetry. Thus, the angular momentum of the photo electron that is created in a chiral electronic transition stems from both the probing electron and the crystal lattice.     

Effect of chromatic aberration on atomic-resolved spherical aberration corrected STEM images

The effect of the chromatic aberration (_Cc)$(C_c)$ coefficient in a spherical aberration (_Cs)$(C_s)$- corrected electromagnetic lens on high-resolution high-angle annular dark field (HAADF) scanning transmission electron microscope (STEM) images is explored in detail. A new method for precise determination of the _Cc$C_c$ coefficient is demonstrated, requiring measurement of an atomic-resolution one-frame through-focal HAADF STEM image. This method is robust with respect to instrumental drift, sample thickness, all lens parameters except _Cc$C_c$, and experimental noise. It is also demonstrated that semi-quantitative structural analysis on the nanometer scale can be achieved by comparing experimental _Cs$C_s$- corrected HAADF STEM images with their corresponding simulated images when the effects of the _Cc$C_c$ coefficient and spatial incoherence are included.     

Energy-filtered transmission electron microscopy based on inner-shell ionization

We demonstrate that energy-filtered transmission electron microscopy (EFTEM) based on inner-shell ionization can contain atomic resolution information. We present a comparison between experimental data and simulation for the EFTEM image of the _N4,5${\mathrm{N}}_{4,5}$ edge (threshold energy 99 eV) of lanthanum in _LaB6${\mathrm{LaB}}_6$ in which direct interpretation of the location of the lanthanum columns is possible. Our first principles approach is based on calculating transition potentials for inelastic scattering. For our case study, the localization of the transition potentials is such that elastic contrast is only weakly preserved in the EFTEM image. This is not always the case, but we show how the approach based on calculating the elastic wave function and the transition potentials can provide insight about when direct interpretation may and may not be possible. In our test specimen, the direct interpretation fails for thicker specimens when the long tails of the transition potential from multiple adjacent sites leads to significant image features other than at the sites of the element of interest. We can thus anticipate instances where direct interpretation may be more reliable, such as looking for a single impurity in an otherwise well known sample.     

Finite-time H∞ control for a class of Markovian jump systems with mode-dependent time-varying delays via new Lyapunov functionals

This paper is concerned with the problem of finite-time _H∞$H_{\infty }$ control for a class of Markovian jump systems with mode-dependent time-varying delays via new Lyapunov functionals. In order to reduce conservatism, a new Lyapunov–Krasovskii functional is constructed. Based on the derived condition, the reliable _H∞$H_{\infty }$ control problem is solved, and the system trajectory stays within a prescribed bound during a specified time interval. Finally, numerical examples are given to demonstrate the proposed approach is more effective than some existing ones.     

H∞ filtering for a class of discrete-time singular Markovian jump systems with time-varying delays

The problem of _H∞$H_{\infty }$ filtering for a class of discrete-time singular Markovian jump systems with time-varying delays is investigated in this paper. The transition probabilities under consideration are time-varying, i.e., Markovian chain is nonhomogeneous. By using the Lyapunov functional approach and reciprocally convex technique, a less conservative delay-dependent bounded real lemma is developed in terms of linear matrix inequalities. Moreover, a sufficient condition for the existence of the desired filter which guarantees the stochastic admissibility and the _H∞$H_{\infty }$ performance index of the resulting filtering error system is presented. Numerical examples are employed to show the usefulness of the proposed results.     

Dielectric measurements of tropical wood

The aim of this paper is to determine the dielectric characteristics of tropical wood species at microwaves frequency in order to use them as planar antenna substrate. The measurements have been done on dried wood in the frequency range 8.2–12.4 GHz. The suitability of wood as a microwave printed antenna substrate will be determined by the values taken by the complex parameters “permittivity” ε$\epsilon$ and “permeability” μ$\mu$ and the loss tangent tanδ$\tan \delta$. The measurement methods were based on the waveguide method and the open resonator technique. The first method gave us the reference values while the second one confirmed the previous measurements. Values obtained in the three principal axis of each species confirm the anisotropic nature of wood. These measurements will also confirm that the losses which are the main criteria of selecting wood as substrate grow with the density of the wood.     

H∞ mode-dependent fault detection filter design for stochastic Markovian jump systems with time-varying delays and parameter uncertainties

This paper deals with the problem of robust _H∞$H_{\infty }$ fault detection for a class of stochastic Markovian jump systems (SMJSs) The aim is to design a linear mode-dependent fault detection filter such that the fault detection system is not only stochastically asymptotically stable in the large, but also satisfies a prescribed _H∞-norm$H_{\infty }\mathrm{-}\mathrm{norm}$ level for all admissible uncertainties. By using Lyapunov stability theory and generalized Itô formula, some novel mode-dependent and delay-dependent sufficient conditions in terms of linear matrix inequality (LMI) are proposed to insure the existence of the desired fault detection filter. A simulation example and an industrial nonisothermal continuous stirred tank reactor (CSTR) system are employed to show the effectiveness of the proposed method.     

Spin–charge separation and electron pairing instabilities in Hubbard nanoclusters

Electron charge and spin pairing instabilities in various cluster geometries for attractive and repulsive electrons are studied exactly under variation of interaction strength, electron doping and temperature. The exact diagonalization, level crossing degeneracies, spin–charge separation and separate condensation of paired electron charge and opposite spins yield intriguing insights into the origin of magnetism, ferroelectricity and superconductivity seen in inhomogeneous bulk nanomaterials and various phenomena in cold fermionic atoms in optical lattices. Phase diagrams resemble a number of inhomogeneous, coherent and incoherent nanoscale phases found recently in high-_Tc$T_c$ cuprates, manganites and multiferroic nanomaterials probed by scanning tunneling microscopy. Separate condensation of electron charge and spin degrees at various crossover temperatures offers a new route for superconductivity, different from the BCS scenario. The calculated phase diagrams resemble a number of inhomogeneous paired phases, superconductivity, ferromagnetism and ferroelectricity found in Nb and Co nanoparticles. The phase separation and electron pairing, monitored by electron doping and magnetic field surprisingly resemble incoherent electron pairing in the family of doped high-_Tc$T_c$ cuprates, ruthenocuprates, iron pnictides and spontaneous ferroelectricity in multiferroic materials.