Search results for " fiber"
showing 10 items of 1776 documents
Insight into Disrupted Spatial Patterns of Human Connectome in Alzheimer’s Disease via Subgraph Mining
2012
Alzheimer’s disease (AD) is the most common cause of age-related dementia, which prominently affects the human connectome. In this paper, the authors focus on the question how they can identify disrupted spatial patterns of the human connectome in AD based on a data mining framework. Using diffusion tractography, the human connectomes for each individual subject were constructed based on two diffusion derived attributes: fiber density and fractional anisotropy, to represent the structural brain connectivity patterns. After frequent subgraph mining, the abnormal score was finally defined to identify disrupted subgraph patterns in patients. Experiments demonstrated that our data-driven approa…
Some comments on the experimental behavior of FRC beams in flexure
2008
In the present paper the experimental results, recently obtained by the authors, regarding the monotonic and the cyclic flexural response of normal and high-strength concrete beams reinforced with steel bars and discontinuous fibers, are shown. From the experimental results, all referred to low values of shear-to-depth ratios, it emerges clearly that the shear failure is brittle especially under cyclic actions highlighting the role of the fibers in the flexural behavior of the beams. The cyclic action produces a significant decay in the stiffness and in the strength capacity of the beams, and the addition of fibers reduces these negative effects. Form theoretical point of view good agreemen…
Behavior in compression of concrete cylinders externally wrapped with basalt fibers
2015
Abstract This paper gives additional information on the use of new class of composites constituted by Basalt Fiber Reinforced Polymer (BFRP) bonded with epoxy resin to concrete specimens as an alternative confinement material for compressed concrete members with respect to carbon or glass fibers. From the experimental point of view, concrete cylinders are wrapped with continuous fibers, in the form of sheets, applying both full and partial discrete wrapping with BFRP straps, and then tested in compression. For comparison, few other concrete cylinders are wrapped with Carbon Fiber Reinforced Polymer (CFRP) sheets and tested in compression. The number and type of plies (full or partial wrappi…
Bleaching of optical activity induced by UV Laser exposure in natural silica
2004
We report experimental data on two types of natural silica, differing for their OH content, irradiated with UV photons (4.66 eV) from a pulsed Nd:YAG laser. Irradiation induces a reduction of the absorption band at 5.12eV and of the associated emissions at 3.14eV and 4.28eV, ascribed to twofold coordinated Ge (=Ge'') centers pre-existing in our samples. The bleaching is mainly due to the post-irradiation conversion of =Ge'' into the paramagnetic H(II) center via trapping of a H atom. Comparison with literature data points out the peculiarities of silica with a low Ge concentration as regards UV induced transformations.
UV-Photoinduced Defects In Ge-Doped Optical Fibers
2005
We investigated the effect of continuous-wave (cw) UV laser radiation on single-mode Ge-doped H2- loaded optical fibers. An innovative technique was developed to measure the optical absorption (OA) induced in the samples by irradiation, and to study its dependence from laser fluence. The combined use of the electron spin resonance (ESR) technique allowed the structural identification of several radiation-induced point defects, among which the Ge(1) (GeO4 -) is found to be responsible of induced OA in the investigated spectral region.
Optical Fibers Enter a New Space-Time Era
2016
We show experimentally a new type of parametric instability associated with the original phenomenon of beam self-cleaning in multimode fibers. Our experimental results are in good agreement with numerical solutions of the Gross-Pitaevskii equation.
Automatic tunable and reconfigurable fiberoptic microwave filters based on a broadband optical source sliced by uniform fiber Bragg gratings.
2002
We demonstrate an automatic tunable transversal notch filter based on uniform fiber Bragg gratings and a broadband optical source. High tunability can be performed by stretching the fiber with the gratings written in series. Also, high sidelobe supression can be achieved by introducing tunable attenuators in a parallel configuration of the gratings.
Trapping of ultracold atoms in a hollow-core photonic crystal fiber
2008
Ultracold sodium atoms have been trapped inside a hollow-core optical fiber. The atoms are transferred from a free space optical dipole trap into a trap formed by a red-detuned gaussian light mode confined to the core of the fiber. We show that at least 5% of the atoms held initially in the free space trap can be loaded into the core of the fiber and retrieved outside.
Towards nonlinear optics with cold Rydberg atoms inside a hollow core fiber
2015
We present an experimental setup for studying strongly nonlinear light-matter interactions using cold atoms inside a hollow core fiber. A Rydberg EIT process can potentially be used to generate strong and tunable effective photon-photon interactions.
Tunable and reconfigurable microwave filter by use of a Bragg-grating-based acousto-optic superlattice modulator
2005
We present an all-optical novel configuration for implementing multitap transversal filters by use of a broadband source sliced by fiber Bragg grating arrays generated by propagating an acoustic wave along a strong uniform fiber Bragg grating. The tunability and reconfigurability of the microwave filter are demonstrated.