5,733 research outputs found
Anisotropic magnetic behavior of GdBa_2Cu_3O_{6+y} single crystals
Magnetic properties of high-quality Al-free nonsuperconducting
GdBa_2Cu_3O_{6+y} single crystals grown by flux method have been studied. The
magnetic anisotropy below the N\'eel temperature T_N~2.3K corresponds to the
direction of Gd^{3+} magnetic moments along the tetragonal c-axis. At T < T_N
clear indications of spin-flop transitions for H||c have been observed on
magnetization curves at H_{sf}~10kOe. Magnetic phase diagrams have been
obtained for H||c as well as for H||ab. A pronounced anisotropy in the magnetic
susceptibility (unexpected for Gd-based compounds) has been found above T_N.Comment: 2 pages, 3 figures; LT23 (Aug. 2002; Hiroshima), accepted to Physica
Magnetic properties of Gd_{1-x}Pr_xBa_2Cu_3O_{7-y} single crystals
Magnetic properties were studied for the high quality Al-free orthorhombic
Gd_{1-x}Pr_xBa_2Cu_3O_{7-y} single crystals (0<=x<=1.0) grown by the flux
method. An indication on the interaction between the Pr and Cu(2) magnetic
sublattices was found for Pr123. Different signs of magnetic anisotropy were
established for the Pr and Gd ions at low temperatures. It was also shown that
superconductivity reported by Zou et al. [Phys. Rev. Lett. 80 (1998) 1074] for
Pr123 single crystals grown by TSZF method seems to be connected with partial
substitution of Ba for the Pr-sites.Comment: 2 pages (LaTeX2e), 4 EPS figures, phbauth style file included. LT22
conference paper accepted to Physica
Current Tomography -- Localization of void fractions in conducting liquids by measuring the induced magnetic flux density
A novel concept of a measurement technology for the localization and
determination of the size of gas bubbles is presented, which is intended to
contribute to a further understanding of the dynamics of efficiency-reducing
gas bubbles in electrolyzers. A simplified proof-of-concept (POC) model is used
to numerically simulate the electric current flow through materials with
significant differences in electrical conductivity. Through an automated
approach, an extensive data set of electric current density and conductivity
distributions is generated, complemented with determined magnetic flux
densities in the surroundings of the POC cell at virtual sensor positions. The
generated data set serves as testing data for various reconstruction
approaches. Based on the measurable magnetic flux density, solving Biot-Savarts
law inversely is demonstrated and discussed with a model-based solution of an
optimization problem, of which the gas bubble locations are derived
In-situ measurements of dendrite tip shape selection in a metallic alloy
The size and shape of the primary dendrite tips determine the principal
length scale of the microstructure evolving during solidification of alloys.
In-situ X-ray measurements of the tip shape in metals have been unsuccessful so
far due to insufficient spatial resolution or high image noise. To overcome
these limitations, high-resolution synchrotron radiography and advanced image
processing techniques are applied to a thin sample of a solidifying Ga-35wt.%In
alloy. Quantitative in-situ measurements are performed of the growth of
dendrite tips during the fast initial transient and the subsequent steady
growth period, with tip velocities ranging over almost two orders of magnitude.
The value of the dendrite tip shape selection parameter is found to be
, which suggests an interface energy anisotropy of
for the present Ga-In alloy. The non-axisymmetric
dendrite tip shape amplitude coefficient is measured to be ,
which is in excellent agreement with the universal value previously established
for dendrites.Comment: 9 pages, 6 figures, submitted to "Physical Reviews Materials
Quantum computing with spatially delocalized qubits
We analyze the operation of quantum gates for neutral atoms with qubits that
are delocalized in space, i.e., the computational basis states are defined by
the presence of a neutral atom in the ground state of one out of two trapping
potentials. The implementation of single qubit gates as well as a controlled
phase gate between two qubits is discussed and explicit calculations are
presented for rubidium atoms in optical microtraps. Furthermore, we show how
multi-qubit highly entangled states can be created in this scheme.Comment: 4 pages, 4 figure
In vitro visual and visible light transillumination methods for detection of natural non-cavitated approximal caries
Objectives
The objective was to evaluate a visible-light-transillumination (using Digital Imaging Fiber-Optic Transillumination machine: DIFOTI) method using occlusal view (DIFOTI-occl), axial view (buccal and lingual: DIFOTI-axial), and combination of all views (DIFOTI-all) for detecting non-cavitated approximal caries and to compare its performance to visual examination (International Caries Detection and Assessment System: ICDAS).
Materials and methods
Thirty extracted human premolars were selected (sound to lesions into the outer one-third of the dentine) based on micro-computed tomography (μ-CT). Teeth were mounted in a custom-made device to simulate approximal contact. DIFOTI (Electro-Optical Sciences Inc., Irvington, NY, USA) images were obtained from the occlusal, buccal, and lingual views. DIFOTI image and ICDAS examinations were performed and repeated by three trained/calibrated examiners. Sensitivity, specificity, area under receiver operating characteristics curve (Az), inter- and intra-class correlation coefficients (ICCs), and correlation were determined.
Results
Sensitivity/specificity was for DIFOTI-occl: 0.42/0.75, DIFOTI-axial: 0.86/0.93, DIFOTI-all: 0.91/0.69, and for ICDAS: 0.89/0.83. Az for DIFOTI-occl was significantly lower than that of DIFOTI-axial (p < 0.001), DIFOTI-all (p = 0.002), and ICDAS (p = 0.005). Spearman correlation coefficients with μ-CT for DIFOTI-occl (r = 0.39) showed weak association, while DIFOTI-axial (r = 0.80), DIFOTI-all (r = 0.91), and ICDAS (r = 0.90) showed moderate association. ICCs for intra-examiner repeatability/inter-examiner agreement were for DIFOTI-occl (0.64/0.58), DIFOTI-axial (0.92/0.89), DIFOTI-all (0.85/0.83), and ICDAS (0.79/0.72).
Conclusions
The results of the current in vitro study suggest that, for detection of non-cavitated approximal caries lesions, DIFOTI performs better using axial than occlusal view
Optimal design under uncertainty of a passive defense structure against snow avalanches: from a general Bayesian framework to a simple analytical model
For snow avalanches, passive defense structures are generally designed by considering high return period events. In this paper, taking inspiration from other natural hazards, an alternative method based on the maximization of the economic benefit of the defense structure is proposed. A general Bayesian framework is described first. Special attention is given to the problem of taking the poor local information into account in the decision-making process. Therefore, simplifying assumptions are made. The avalanche hazard is represented by a Peak Over Threshold (POT) model. The influence of the dam is quantified in terms of runout distance reduction with a simple relation derived from small-scale experiments using granular media. The costs corresponding to dam construction and the damage to the element at risk are roughly evaluated for each dam height-hazard value pair, with damage evaluation corresponding to the maximal expected loss. Both the classical and the Bayesian risk functions can then be computed analytically. The results are illustrated with a case study from the French avalanche database. A sensitivity analysis is performed and modelling assumptions are discussed in addition to possible further developments
High rate production of polarized 3He with meta-stability exchange method
Keywords: polarized 3He, meta-stability exchange, infrared laserComment: 4 figures, submitted to J. Phys. Soc. Jpn
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