Effect of Debonding in Fiber-Reinforced Compsites on Ultrasonic Backscattering

With the increased use of new high strength materials such as fiber-reinforced composites, the need for NDE methods is obvious, especially in industries such as the aerospace industry. The particular defect studied here (debonding of fiber from the matrix) is particularly important as it is often the earliest sign of fatigue damage in fiber-reinforced laminates [9]. Having an ability to detect such damage is clearly necessary and the application of ultrasound may provide a cheap and rapid method of detection. This paper presents two theoretical models of the effect of debonds on ultrasonic backscattering, and compares them with the experimental results from scale models of a single debonded fiber

Design of an exhaust mixer nozzle for the Avco-Lycoming Quiet Clean General Aviation Turbofan (QCGAT)

This report describes the design configuration and method used to design the forced engine exhaust to bypass air mixing system for Lycoming's QCGAT engine. This mixer is an integral part of the total engine and nacelle system and was configured to reduce the propulsion system noise and fuel consumption levels

Identification of amino acid residues of the NR2A subunit that control glutamate potency in recombinant NR1/NR2A NMDA receptors

The NMDA type of ligand-gated glutamate receptor requires the presence of both glutamate and glycine for gating. These receptors are hetero-oligomers of NR1 and NR2 subunits. Previously it was thought that the binding sites for glycine and glutamate were formed by residues on the NR1 subunit. Indeed, it has been shown that the effects of glycine are controlled by residues on the NR1 subunit, and a “Venus flytrap” model for the glycine binding site has been suggested by analogy with bacterial periplasmic amino acid binding proteins. By analysis of 10 mutant NMDA receptors, we now show that residues on the NR2A subunit control glutamate potency in recombinant NR1/NR2A receptors, without affecting glycine potency. Furthermore, we provide evidence that, at least for some mutated residues, the reduced potency of glutamate cannot be explained by alteration of gating but has to be caused primarily by impairing the binding of the agonist to the resting state of the receptor. One NR2A mutant, NR2A(T671A), had anEC50for glutamate 1000-fold greater than wild type and a 255-fold reduced affinity for APV, yet it had single-channel openings very similar to those of wild type. Therefore we propose that the glutamate binding site is located on NR2 subunits and (taking our data together with previous work) is not on the NR1 subunit. Our data further imply that each NMDA receptor subunit possesses a binding site for an agonist (glutamate or glycine).</jats:p

A Critical Analysis of the Theoretical Basis of Ultrasonic Scattering Measurements

There are three elements involved in the backscattering from inhomogeneous media; the scattering properties of a single particle or scattering element, the scattering associated with a group of such particles and the relationship of the scattered wave to the measured signal. Ideally it should be possible to obtain information about the material microstructure from ultrasonic backscattering measurements. However, a number of assumptions and approximations must be made before the problem becomes tractable, and it is the purpose of the present investigation to compare the various approaches available in the literature in an attempt to quantify the errors involved with some of these approximations

J/Ѱ polarization in p+p collisions at √s = 200 GeV in STAR

We report on a polarization measurement of inclusive J/Ѱ mesons in the di-electron decay channel at mid-rapidity at 2 \u3c pT \u3c 6 GeV/c in p + p collisions at √s = 200 GeV. Data were taken with the STAR detector at RHIC. The J/Ѱ polarization measurement should help to distinguish between different models of the J/Ѱ production mechanism since they predict different pT dependences of the J/Ѱ polarization. In this analysis, J/Ѱ is studied in the helicity frame. The polarization parameter λθ measured at RHIC becomes smaller towards high pT, indicating more longitudinal J/Ѱ polarization as pT increases. The result is compared with predictions of presently available models

ΛΛ Correlation Function in Au+Au Collisions at √\u3cem\u3e\u3csup\u3eS\u3c/sup\u3e\u3csub\u3eNN\u3c/sub\u3e\u3c/em\u3e=200 GeV

We present ΛΛ correlation measurements in heavy-ion collisions for Au+Au collisions at √SNN=200  GeV using the STAR experiment at the Relativistic Heavy-Ion Collider. The Lednický-Lyuboshitz analytical model has been used to fit the data to obtain a source size, a scattering length and an effective range. Implications of the measurement of the ΛΛ correlation function and interaction parameters for dihyperon searches are discussed

Beam-Energy-Dependent Two-Pion Interferometry and the Freeze-Out Eccentricity of Pions Measured in Heavy Ion Collisions at the STAR Detector

We present results of analyses of two-pion interferometry in Au+Au collisions at √SNN=7.7, 11.5, 19.6, 27, 39, 62.4, and 200 GeV measured in the STAR detector as part of the BNL Relativistic Heavy Ion Collider Beam Energy Scan program. The extracted correlation lengths (Hanbury-Brown–Twiss radii) are studied as a function of beam energy, azimuthal angle relative to the reaction plane, centrality, and transverse mass (mT) of the particles. The azimuthal analysis allows extraction of the eccentricity of the entire fireball at kinetic freeze-out. The energy dependence of this observable is expected to be sensitive to changes in the equation of state. A new global fit method is studied as an alternate method to directly measure the parameters in the azimuthal analysis. The eccentricity shows a monotonic decrease with beam energy that is qualitatively consistent with the trend from all model predictions and quantitatively consistent with a hadronic transport model

Measurement of Longitudinal Spin Asymmetries for Weak Boson Production in Polarized Proton-Proton Collisions at RHIC

We report measurements of single- and double-spin asymmetries for W± and Z/γ∗ boson production in longitudinally polarized p+p collisions at √S=510  GeV by the STAR experiment at RHIC. The asymmetries for W± were measured as a function of the decay lepton pseudorapidity, which provides a theoretically clean probe of the proton’s polarized quark distributions at the scale of the W mass. The results are compared to theoretical predictions, constrained by polarized deep inelastic scattering measurements, and show a preference for a sizable, positive up antiquark polarization in the range 0.05\u3cx\u3c0.2

\u3cem\u3eJ\u3c/em\u3e/\u3cem\u3eψ\u3c/em\u3e Production at Low \u3cem\u3ep\u3csub\u3eT\u3c/sub\u3e\u3c/em\u3e in Au + Au and Cu + Cu Collisions at √\u3cem\u3e\u3csup\u3eS\u3c/sup\u3eNN\u3c/em\u3e = 200 GeV with the STAR Detector

The J/ψ pT spectrum and nuclear modification factor (RAA) are reported for pT \u3c 5 GeV/c and |y| \u3c 1 from 0% to 60% central Au + Au and Cu + Cu collisions at √SNN = 200 GeV at STAR. A significant suppression of pT-integrated J/ψ production is observed in central Au + Au events. The Cu + Cu data are consistent with no suppression, although the precision is limited by the available statistics. RAA in Au + Au collisions exhibits a strong suppression at low transverse momentum and gradually increases with pT. The data are compared to high-pT STAR results and previously published BNL Relativistic Heavy Ion Collider results. Comparing with model calculations, it is found that the invariant yields at low pT are significantly above hydrodynamic flow predictions but are consistent with models that include color screening and regeneration

Beam-Energy Dependence of Charge Separation Along the Magnetic Field in Au+Au Collisions at RHIC

Local parity-odd domains are theorized to form inside a quark-gluon plasma which has been produced in high-energy heavy-ion collisions. The local parity-odd domains manifest themselves as charge separation along the magnetic field axis via the chiral magnetic effect. The experimental observation of charge separation has previously been reported for heavy-ion collisions at the top RHIC energies. In this Letter, we present the results of the beam-energy dependence of the charge correlations in Au+Au collisions at midrapidity for center-of-mass energies of 7.7, 11.5, 19.6, 27, 39, and 62.4 GeV from the STAR experiment. After background subtraction, the signal gradually reduces with decreased beam energy and tends to vanish by 7.7 GeV. This implies the dominance of hadronic interactions over partonic ones at lower collision energies