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The mechanical work output of simplified pyrotechnic igniters for research investigations is statistically characterized by monitoring the post-ignition external flow field with Schlieren imaging. Unique to this work is a detailed quantification of all measurable manufacturing parameters (e.g., bridgewire length, charge cavity dimensions, powder bed density) and associated shock-motion variability in the tested igniters. A statistically-significant population of manufactured igniters were tested within the Schlieren arrangement resulting in a characterization of the nominal output. Comparisons between the variances measured throughout the manufacturing processes and the observed output provide insight into the critical device phenomena that dominate performance. [ABSTRACT FROM AUTHOR]

This paper comprises two separate parts. First, we present the high-spin states in 139Pm nucleus. Two negative-parity dipole bands have been observed and assigned as πh11/2xν(h11/2)-2 and πh11/2xν(h11/2)-4 configurations. From the systematic comparison with neighboring nuclei and SPAC (Shears mechanism with Principal Axis Cranking) model calculations, the two bands can be suggested as magnetic rotational bands. In the other part of this paper, the construction of one new array of eight Clover and sixteen HPGe detectors has been introduced. The characteristics of the Clover detector have been presented and compared with Geant4 simulations. [ABSTRACT FROM AUTHOR]

Over the past twenty years acoustic emission (AE) has been studied for applications to the structural health monitoring (SHM) of metallic structures. The success of AE for prognosis of in-service steel bridges depends on the reliability of the received AE signals. The emphasis of this paper is on the characterization of acoustic emission source mechanisms for ASTM A572 grade 50 steel. The source characterization was aided by Digital Imaging Correlation (DIC) and Scanning Electronic Microscopy (SEM). The results indicate that both ductile and brittle mechanisms can produce AE during fatigue crack growth in the steel. However, the fracture mechanisms are predominately ductile. A key preliminary finding is that fatigue crack extension does not generally produce AE events in the early stage of fatigue crack growth for the steel bridge material investigated. [ABSTRACT FROM AUTHOR]

High-spin states in 189Pt have been studied with the in-beam γ-spectroscopy method via the 176Yb(18O,5n) reaction at beam energies of 88 MeV and 95 MeV. A new level scheme of 189Pt has been established. Rotational bands based on the υi13/2-1, υf5/2(p3/2) and υi13/2-2υf5esol2(p3/2) configurations, as well as several structures with irregular level spacings, have been observed. Properties of rotational bands have been analyzed in the framework of triaxial particle-rotor model. A γ~-30° triaxial shape and a near prolate shape have been proposed to the υi13/2-1 and υf5/2(p3/2) bands, respectively. Two ΔI = 2 transition sequences with similar energies have been observed, and they have been proposed to be associated with the υi13/2-2υf5/2(p3/2) configuration. According to the relevant Nilsson orbitals, the bands built on the υi13/2-2υf5/2(p3/2) configuration could be interpreted as a pair of pseudo-spin partner. [ABSTRACT FROM AUTHOR]

During the last decade, experimental and theoretical results induced a change of paradigm for the Reversed Field Pinch, (RFP). Indeed, experiments in present generation devices back up the new theoretical understanding of this alternative configuration for magnetic confinement: the basic nature of the system can be described as a self-organized helical state corresponding to the nonlinear saturation of a kink-tearing mode. This perspective was somewhat anticipated by older pioneering 3D nonlinear MHD. Very importantly from a theoretical point of view and with respect to confinement properties, the existence of RFP equilibrium with perfectly conserved helical confining magnetic surfaces comes into play. This is at variance with the previous traditional idea of the RFP as a relaxed axis-symmetric state, which, by theoretical arguments, requires the action of turbulence to accomplish and to maintain relaxation. In this presentation we propose a summary and discussion of the achievements in this subject, including results from 3D nonlinear MHD simulations, related transport effects and present open issues. Major relevant experimental facts are also surveyed. [ABSTRACT FROM AUTHOR]

Electric fields in the GaN underlying the 2DEG of three GaN/AlGaN field effect transistor (FET) structures measured by photoreflectance (PR) using sub-gap excitation were found to be about 210–260kVcm-1, indicating the presence of traps. The sample having the lowest electric field was taken from a wafer which yielded 0.3μm gate length devices having the highest power gain performance metrics; the sample with the highest electric field corresponded to devices having the lowest power gain metric. A self-consistent Poisson calculation determined the density of traps to be ca. 1017 cm-3. This density of traps is similar to other trap density measurements in FETs. These results suggest that PR could be used as a non-destructive probe of trap density in the underlying GaN. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]