Analysis of edge impact stresses in composite plates

The in-plane edge impact of composite plates, with or without a protection strip, is investigated. A computational analysis based on the Fast Fourier Transform technique is presented. The particular application of the present method is in the understanding of the foreign object damage problem of composite fan blades. The method is completely general and may be applied to the study of other stress wave propagation problems in a half space. Results indicate that for the protective strip to be effective in reducing impact stresses in the composite the thickness must be equal or greater than the impact contact dimension. Large interface shear stresses at the strip - composite boundary can be induced under impact

Large amplitude flutter of a low aspect ratio panel at low supersonic speeds comparison of theory and experiment

Flutter boundaries, as well as flutter limit cycle amplitudes, frequencies and stresses were computed for a panel of length-width ratio 4.48 exposed to applied in-plane and transverse loads. The Mach number range was 1.1 to 1.4. The method used involved direct numerical integration of modal equations of motion derived from the nonlinear plate equations of von Karman, coupled with linearized potential flow aerodynamic theory. The flutter boundaries agreed reasonably well with experiment, except when the in-plane loading approached the buckling load. Structural damping had to be introduced, to produce frequencies comparable to the experimental values. Attempts to compute panel deflections or stress at a given point met with limited success. There is some evidence, however, that deflection and stress maxima can be estimated with somewhat greater accuracy

Neutrino Oscillations and Lepton Flavor Mixing

In view of the recent announcement on non-zero neutrino mass from Super-Kamiokande experiment, it would be very timely to investigate all the possible scenarios on masses and mixings of light neutrinos. Recently suggested mass matrix texture for the quark CKM mixing, which can be originated from the family permutation symmetry and its suitable breakings, is assumed for the neutrino mass matrix and determined by the four combinations of solar, atmospheric and LSND neutrino data and cosmological hot dark matter bound as input constraints. The charged-lepton mass matrix is assumed to be diagonal so that the neutrino mixing matrix can be identified directly as the lepton flavor mixing matrix and no CP invariance violation originates from the leptonic sector. The results favor hierarchical patterns for the neutrino masses, which follow from the case when either solar-atmospheric data or solar-HDM constraints are used.Comment: Latex, 9 page

Magnetic field splitting of the spin-resonance in CeCoIn5

Neutron scattering in strong magnetic fields is used to show the spin-resonance in superconducting CeCoIn5 (Tc=2.3 K) is a doublet. The underdamped resonance (\hbar \Gamma=0.069 \pm 0.019 meV) Zeeman splits into two modes at E_{\pm}=\hbar \Omega_{0}\pm g\mu_{B} \mu_{0}H with g=0.96 \pm 0.05. A linear extrapolation of the lower peak reaches zero energy at 11.2 \pm 0.5 T, near the critical field for the incommensurate "Q-phase" indicating that the Q-phase is a bose condensate of spin excitons.Comment: 5 pages, 4 figure

Approximate 3-Dimensional Electrical Impedance Imaging

We discuss a new approach to three-dimensional electrical impedance imaging based on a reduction of the information to be demanded from a reconstruction algorithm. Images are obtained from a single measurement by suitably simplifying the geometry of the measuring chamber and by restricting the nature of the object to be imaged and the information required from the image. In particular we seek to establish the existence or non-existence of a single object (or a small number of objects) in a homogeneous background and the location of the former in the (x,y)-plane defined by the measuring electrodes. Given in addition the conductivity of the object rough estimates of its position along the z-axis may be obtained. The approach may have practical applications.Comment: 12 pages, 4 figures, LaTeX, Appendix added and other minor change

Evolution of Magnetic and Superconducting Fluctuations with Doping of High-Tc Superconductors

Electronic Raman scattering from high- and low-energy excitations was studied as a function of temperature, extent of hole doping, and energy of the incident photons in Bi_2Sr_2CaCu_2O_{8 \pm \delta} superconductors. For underdoped superconductors, short range antiferromagnetic (AF) correlations were found to persist with hole doping, and doped single holes were found to be incoherent in the AF environment. Above the superconducting (SC) transition temperature T_c, the system exhibits a sharp Raman resonance of B_{1g} symmetry and energy of 75 meV and a pseudogap for electron-hole excitations below 75 meV, a manifestation of a partially coherent state forming from doped incoherent quasi particles. The occupancy of the coherent state increases with cooling until phase ordering at T_c produces a global SC state.Comment: 6 pages, 4 color figures, PDF forma

Low scale Seesaw model and Lepton Flavor Violating Rare B Decays

We study lepton flavor number violating rare B decays, $b \to s l_h^{\pm} l_l^{\mp}$, in a seesaw model with low scale singlet Majorana neutrinos motivated by the resonant leptogenesis scenario. The branching ratios of inclusive decays $b \to s l_h^{\pm} \bar{l_l}^{\mp}$ with two almost degenerate singlet neutrinos at TeV scale are investigated in detail. We find that there exists a class of seesaw model in which the branching fractions of $b \to s \tau \mu$ and $\tau \to \mu \gamma$ can be as large as $10^{-10}$ and $10^{-9}$ within the reach of Super B factories, respectively, without being in conflict with neutrino mixings and mass squared difference of neutrinos from neutrino data, invisible decay width of $Z$ and the present limit of $Br(\mu \to e \gamma)$.Comment: 19 pages, 6 figure

Zero-Bias Anomalies in Narrow Tunnel Junctions in the Quantum Hall Regime

We report on the study of cleaved-edge-overgrown line junctions with a serendipitously created narrow opening in an otherwise thin, precise line barrier. Two sets of zero-bias anomalies are observed with an enhanced conductance for filling factors $\nu > 1$ and a strongly suppressed conductance for $\nu < 1$. A transition between the two behaviors is found near $\nu \approx 1$. The zero-bias anomaly (ZBA) line shapes find explanation in Luttinger liquid models of tunneling between quantum Hall edge states. The ZBA for $\nu < 1$ occurs from strong backscattering induced by suppression of quasiparticle tunneling between the edge channels for the $n = 0$ Landau levels. The ZBA for $\nu > 1$ arises from weak tunneling of quasiparticles between the $n = 1$ edge channels.Comment: version with edits for clarit

Cascade of Quantum Phase Transitions in Tunnel-Coupled Edge States

We report on the cascade of quantum phase transitions exhibited by tunnel-coupled edge states across a quantum Hall line junction. We identify a series of quantum critical points between successive strong and weak tunneling regimes in the zero-bias conductance. Scaling analysis shows that the conductance near the critical magnetic fields $B_{c}$ is a function of a single scaling argument $|B-B_{c}|T^{-\kappa}$, where the exponent $\kappa = 0.42$. This puzzling resemblance to a quantum Hall-insulator transition points to importance of interedge correlation between the coupled edge states.Comment: 4 pages, 3 figure