Search results for "edge"
showing 10 items of 3866 documents
A new BeppoSAX observation of the Z Source GX 349+2
2004
Abstract We report on the results from two BeppoSAX observations of the Z source GX 349+2 performed in February 2001 and covering the broad energy range 0.12–200 keV. The average spectrum is well described by a soft blackbody (kTBB∼0.5 keV) and a Comptonized component having a seed-photon temperature of kT0∼1 keV, an electron temperature of kTe∼2.7 keV, and optical depth τ∼11. To well fit the energy spectrum three gaussian lines are needed at 1.2 keV, 2.6 keV, and 6.7 keV with corresponding equivalent widths of 13 eV, 10 eV, and 39 eV, probably associated to L-shell emission of Fe XXIV, Lyα S XVI, and Fe XXV, respectively. These lines may be produced at different distances from the neutron …
STUDIES OF WIRE GAIN AND TRACK DISTORTION NEAR THE SECTOR EDGES OF THE ALEPH TIME PROJECTION CHAMBER
1986
Abstract The materials used to hold the wires at the sector edges in a large Time Projection Chamber (TPC) inrtoduce distortions of the electric drift field near those edges. These distortions degrade tracking information and sometimes cause large changes in wire gain near the edge. We have studied these two problems for the ALEPH TPC and have found that both can be greatly reduced by the addition of two field correction strips held at appropriate voltages.
Novel digital K-edge imaging system with transition radiation from an 855-MeV electron beam
2001
A novel K-edge imaging method has been developed at the Mainz Microtron MAMI aiming at a very efficient use of the transition radiation (TR) flux generated by the external 855-MeV electron beam in a foil stack. A fan-like quasi-monochromatic hard X-ray beam is produced from the /spl plusmn/1-mrad-wide TR cone with a highly oriented pyrolytic graphite (HOPG) crystal. The absorption of the object in front of a 30 mm/spl times/10 mm pn charge-coupled device (pn-CCD) photon detector is measured at every pixel by a broad-band energy scan around the K-absorption edge. This is accomplished by a synchronous variation of the lateral crystal position and the electron beam direction which defines also…
Ideality factor behavior between the maximum power point and open circuit
2013
The local ideality factor analysis of dark and light I-V curves has been used in the past to study various performance degradation effects in solar cells. Trapping, edge recombination and injection-level-dependent recombination are expressed as “lumps, humps and bumps” in the plots of the local ideality factor over cell voltage (m-V plots). Earlier applications of this differential technique did not correct the plots for the series resistance effect. Thus, the bumps at the higher voltages introduced by some mechanisms were more difficult to quantify. A possible solution is to analyze ISC-VOC curves, but their measurement is not always possible. We present a formula for calculation of the RS…
Critical Wetting and Interface Localization—Delocalization Transition in a Double Wedge
2004
Using Monte Carlo simulations and finite-size scaling methods we study “wetting” in Ising systems in a L x L x L y pore with quadratic cross section. Antisymmetric surface fields H s act on the free L x L y surfaces of the opposing wedges, and periodic boundary conditions are applied along the y-direction. Our results represent the first simulational observation of fluctuation effects in three dimensional wetting phenomena and corroborate recent predictions on wedge filling. In the limit L → ∞ L y /L 3 = const the system exhibits a new type of phase transition, which is the analog of the “filling transition” that occurs in a single wedge. It is characterized by critical exponents α = 3/4, β…
Improving the performance of CdZnTe detectors using infrared stimulation
2011
The influence of monochromatic optical stimulation with wavelengths from 400 nm to 1100 on characteristics of the CdZnTe quasi-hemispherical detectors was studied. It was found that illumination with infrared (IR) light of wavelengths (870–900 nm) close to the absorption edge of the CdZnTe significantly improves the detectors performance at room temperature. Improvement can be achieved with low-intensity IR illumination of about 1–10 µW. The higher intensity illumination leads to degradation of the detector spectrometric characteristics. Infrared radiation penetrates into the detector sensitive volume, change the balance equilibrium between free and trapped carriers, leading to improve char…
Xrase: The X-Ray Spectroscopic Explorer
2001
The X-Ray Spectroscopic Explorer (XRASE) has a unique combination of features that will make it possible to address many of NASA’s scientific goals. These include how galaxy clusters form, the physics and chemistry of the ISM, the heating of stellar coronae, the amount and content of intergalactic baryonic matter, the mass of black holes and the formation of disks and jets in AGN and galactic binaries. XRASE has a thin foil, multilayered telescope with a large collecting area up to 10 keV, especially in the Fe Kα region (1100 cm2). Its microcalorimeter array combines high energy resolution (7 eV at 6 keV) and efficiency with a field-of-view of 26 arcmin2. A deep orbit allows for long, conti…
Oscillatory Localization of Quantum Walks Analyzed by Classical Electric Circuits
2016
We examine an unexplored quantum phenomenon we call oscillatory localization, where a discrete-time quantum walk with Grover's diffusion coin jumps back and forth between two vertices. We then connect it to the power dissipation of a related electric network. Namely, we show that there are only two kinds of oscillating states, called uniform states and flip states, and that the projection of an arbitrary state onto a flip state is bounded by the power dissipation of an electric circuit. By applying this framework to states along a single edge of a graph, we show that low effective resistance implies oscillatory localization of the quantum walk. This reveals that oscillatory localization occ…
Topologically Protected Twist Edge States for a Resonant Mechanical Laser-Beam Scanner
2019
We design a one-dimensional chain of two different alternating three-dimensional elastic chiral unit cells. The chain’s topological band gap, a result of the alternation of unit cells combined with their chirality and an effective mirror symmetry, guarantees a protected edge state, corresponding to a localized twist mode with an eigenfrequency inside the one-dimensional band gap. A small axial modulation at the one end of the beam can excite this resonant twist mode at the other end of the beam, via evanescent modes in the gap. The topological robustness of the edge state allows us to add a micromirror to the other end of the beam, turning the arrangement into a resonant mechanical laser-be…
An extended Ritz formulation for buckling and post-buckling analysis of cracked multilayered plates
2018
Abstract An extended Ritz formulation for the analysis of buckling and post-buckling behaviour of cracked composite multilayered plates is presented. The formulation is based on: (i) the First-order Shear Deformation Theory to model the mechanics of the multilayered plate; (ii) the von Karman’s theory to account for geometric non-linearities ; (iii) the use of an extended set of approximating functions able to model the presence of an embedded or edge crack and to capture the crack opening fields as well as the global behaviour within a single cracked domain. The numerical results of the buckling analyses and the equilibrium paths in the post-buckling regime are compared with the results fr…