Effects of hysteretic and aerodynamic damping on supersonic panel flutter of composite plates

The governing equation for the finite element analysis of the panel flutter of composite plates including structural damping is derived from Hamilton's principle. The first order shear deformable plate theory has been applied to structural modelling so as to obtain the finite element eigenvalue equation. The unsteady aerodynamic load in a supersonic flow is computed by using the linear piston theory. The critical dynamic pressures for composite plates have been calculated to investigate the effects of structural damping on flutter boundaries. The effects are dependent on fiber orientation because flutter mode can be weak or strong in the fiber orientation of composite plates. Structural damping plays an important role in flutter stability with low aerodynamic damping but would not affect the flutter boundary with high aerodynamic damping.     

Band bending at the Ni/Si(100)-2×1 submonolayer interface

Band bending at the Ni/Si(100)-2×1 interface has been monitored by using Si 2p core level photoemission spectra. Two nickel-induced Si 2p components appear in the initial interaction between Ni and Si(100)-2×1, which is confined at the top surface and the first subsurface layers. At Ni coverage less than 0.0375 ML, Ni atoms prefer the adamantane interstitial sites on the first subsurface, but switch to the pedestal sites on Si dimer rows at higher Ni coverage. The change in the preferred occupation sites of Ni atoms on the Si(100)-2×1 surface strongly affects the amount of band bending shift. The shift towards higher binding energy, when Ni atoms occupy the adamantane interstitial sites, is attributed to metal-induced-gap states. While Ni atoms occupy the pedestal sites, the band bending shift is reduced which is attributed to the passivation of surface states.     

Regular and alternant spiral waves of contractile motion on rat ventricle cell cultures

We demonstrate that meandering as well as regular spiral waves can form in a well-controlled culture layer of rat ventricle cells and that the meandering spiral wave, in particular, can generate an alternant rhythm. These observations are made possible by a newly developed, noninvasive phase contrast macro-optics that is simple but highly effective in visualizing the contractile motion of the populations of cardiac cells.     

Disordered RKKY lattice mean field theory for ferromagnetism in diluted magnetic semiconductors

We develop a lattice mean field theory for ferromagnetic ordering in diluted magnetic semiconductors by taking into account the spatial fluctuations associated with random disorder in the magnetic impurity locations and the finite mean free path associated with low carrier mobilities. Assuming a carrier-mediated indirect RKKY exchange interaction among the magnetic impurities, we find substantial deviation from the extensively used continuum Zener model Weiss mean field predictions. Our theory allows accurate analytic predictions for Tc and provides simple explanations for a number of observed anomalies, including the non-Brillouin function magnetization curves, the suppressed low-temperature magnetization saturation, and the dependence of Tc on conductivity.     

Effects of substrate treatment on the electroluminescence performance of flexible OLEDs

Electroluminescence (EL) performance of flexible organic light-emitting device (FOLED) has been found to be highly dependent upon the morphology of the surface of the indium thin oxide (ITO)/plastic substrate as well as the patterning and processing conditions of the substrate. We will present evidence showing that luminance efficiency of FOLED can be greatly improved by pretreatment. Surface analysis of the ITO/PET by means of atomic force microscope (AFM) and optical microscope will be compared with that of the ITO/glass and the influence of flexible OLEDs substrate treatment by various methods on EL performance will also be discussed.     

Photoemission study of CaF2 on Si(001)-2×1 during annealing

We have employed synchrotron radiation photoemission to investigate calcium fluoride deposited on Si(001)-2×1 annealed at 700 °C. The valence band spectra reveal that the initial molecules are dissociated to single Ca atoms resting on the surface. Si 2p core-level spectra manifest a negatively shifted Ca-induced line at 0.35 eV. The dissociated Ca atoms occupy only half of the surface, on top of which the CaF₂ molecules commence growth. This is in contrast to the Si(111)-7×7 counterpart, which exhibits a CaF layer in the interface. Strong elastic scattering due to the absorbed Ca atoms is evident in the photoemission spectra, thus averaging out the angle-dependent features.     

Transport and percolation in a low-density high-mobility two-dimensional hole system

We present a study of the temperature and density dependence of the resistivity of an extremely high quality two-dimensional hole system grown on the (100) surface of GaAs. For high densities in the metallic regime (p > or approximately4x10;{9} cm;{-2}), the nonmonotonic temperature dependence ( approximately 50-300 mK) of the resistivity is consistent with temperature dependent screening of residual impurities. At a fixed temperature of T=50 mK, the conductivity versus density data indicate an inhomogeneity driven percolation-type transition to an insulating state at a critical density of 3.8x10;{9} cm;{-2}.     

Carrier transport in two-dimensional graphene layers

Carrier transport in gated 2D graphene monolayers is considered in the presence of scattering by random charged impurity centers with density n(i). Excellent quantitative agreement is obtained (for carrier density n>10(12) cm(-2)) with existing experimental data. The conductivity scales linearly with n/n(i) in the theory. We explain the experimentally observed asymmetry between electron and hole conductivities, and the high-density saturation of conductivity for the highest mobility samples. We argue that the experimentally observed saturation of conductivity at low density arises from the charged impurity induced inhomogeneity in the graphene carrier density which becomes severe for n less, similarn(i) approximately 10(12) cm(-2).     

Performance limits of pico-cell systems using radio-over-fiber techniques with an electroabsorption modulator

We investigate the performance limits of a pico-cell system using the radio- over-fiber technique with an electroabsorption modulator (EAM) in a 2.4 GHz wireless local area network (WLAN) environment. To understand the performance limits of the system using an EAM as the optical transceiver, we vary the optical modulation index (OMI) of the transmitter for different bias voltages to the EAM. Power margins in the links are found to estimate a possible service range, and packet loss rates (PLRs) in the pico-cell system are measured to evaluate the transmission performance. The total service range can be extended up to 3 m by adjusting the OMI of the transmitter for different applied bias voltages to the EAM.