X-Ray Cone Beam Tomography with Two Tilted Circular Trajectories

Recently 3-D cone-beam tomography has become of interest for the nondestructive evaluation of advanced materials. The main field of application in nondestructive testing is the evaluation of structural ceramics. Study of such materials implies high density resolution and high sensitivity to cracks. In fact, with a single circular source trajectory, when the cone-beam aperture increases, density is underestimated and cone shaped artifacts may appear at interfaces in the sample even at relatively small aperture [1–3]. These artifacts limit the thickness we can examine with a planar source trajectory. To maintain optimal reconstruction accuracy with a circular source trajectory, the angular aperture must remain within ±10°. However Kudo and Saito [4] showed that this limit can be slightly overcome by using a special interpolation of the shadow area. But to examine greater thicknesses and to maintain resolution, we must widen the cone-beam aperture thereby decreasing accuracy. To overcome these aperture limitations, Tuy [5] introduced the double circular source trajectory idea

Development of an Advanced 3D Cone Beam Tomographic System

While 2D x-ray CT is now commonly used for NDT applications, the interest in 3D x-ray cone beam tomography has significantly increased over the last few years [1,2]. The need to reduce acquisition time for industrial applications, or radiation dose to patients for medical applications, led engineers to develop a new type of tomograph using x-ray beams more efficiently. Thanks to a high spatial resolution, the 3D x-ray CT allows greater knowledge of the object structure. This understanding is necessary to study and improve industrial production of high technology materials. Therefore, 3D x-ray CT is well suited for the study of materials with structural anomalies, such as technical ceramics [2]

Nematodes of forage legumes and grasses: Catalogue and Bibliography 1961- 1985

Se presentan 1 catalogo y 1 bibliografia sobre investigaciones relacionadas con el efecto de nematodos en gramineas y leguminosas forrajeras. En la seccion de catalogo, se incluyen nombres cientificos de plantas forrajeras (gramineas y leguminosas), nombres cientificos de nematodos asociados con ellas, pais donde se registro o se estudio el nematodo y no. de registro bibliografico. La bibliografia esta compuesta por 840 referencias bibliograficas (la mayoria con resumen) de trabajos de investigacion sobre nematodos y un listado de 308 referencias bibliograficas de registros unicos de asociaciones entre plantas y nematodos. (CIAT

X-Ray Quantitative Evaluation of Multi-Layered Objects from Few Projections: A Multiresolution Technique

In this paper, we present the results of a study[1] motivated by the radiographic inspection of solder joints on double-sided printed circuits. Our goal was to obtain quantitative information about the structures in these planar objects, taking into account the acquisition geometry and time constraints. On one hand, we must limit the acquisition angle for projections at a value of ± 50 degrees with respect to the normal to the object plane, in order to limit the attenuation of the material crossed by X-rays. On the other hand, we must limit the number of projections in order to reduce as far as possible the acquisition and processing times

Compact cryogenic Kerr microscope for time-resolved studies of electron spin transport in microstructures

A compact cryogenic Kerr microscope for operation in the small volume of high-field magnets is described. It is suited for measurements both in Voigt and Faraday configuration. Coupled with a pulsed laser source, the microscope is used to measure the time-resolved Kerr rotation response of semiconductor microstructures with ~1 micron spatial resolution. The microscope was designed to study spin transport, a critical issue in the field of spintronics. It is thus possible to generate spin polarization at a given location on a microstructure and probe it at a different location. The operation of the microscope is demonstrated by time-resolved measurements of micrometer distance diffusion of spin polarized electrons in a GaAs/AlGaAs heterojunction quantum well at 4.2 K and 7 Tesla

Suppressed spin dephasing for 2D and bulk electrons in GaAs wires due to engineered cancellation of spin-orbit interaction terms

We report a study of suppressed spin dephasing for quasi-one-dimensional electron ensembles in wires etched into a GaAs/AlGaAs heterojunction system. Time-resolved Kerr-rotation measurements show a suppression that is most pronounced for wires along the [110] crystal direction. This is the fingerprint of a suppression that is enhanced due to a strong anisotropy in spin-orbit fields that can occur when the Rashba and Dresselhaus contributions are engineered to cancel each other. A surprising observation is that this mechanisms for suppressing spin dephasing is not only effective for electrons in the heterojunction quantum well, but also for electrons in a deeper bulk layer.Comment: 5 pages, 3 figure

Impact of texture TDS and flavour TDS tasks and of chocolate-chip biscuit characteristics on oral processing features

[EN] The objective of the present study was to investigate differences in oral activity when biscuits of the same type but with subtle composition differences are consumed and how performing a Temporal Dominance of Sensations (TDS) task modifies the way one eats. In addition, comparisons were made between performing a texture TDS (T-TDS) and a flavour TDS (F-TDS). Oral activity while eating biscuits with and without conducting a TDS task was recorded using a 3.dimensional motion capture system to monitor the evolution of jaw movements. The results showed that oral activity evolved over the consumption time, differed depending on the texture of the sample and was affected to a small but significant extent when a TDS task was performed simultaneously (the differences averaged < 4 cycles, 1 s in duration, 0.1 cycles/s in frequency, and 1 mm in lateral displacement). The biscuit samples were affected equally. Almost no differences were found on comparing oral activity during the execution of the T-TDS and the F-TDS tasks. Overall, the present results show differences in oral activity even for food products of the same category with subtle differences in composition. Performing TDS tasks (regardless of their modality) during sample consumption affected the total number, frequency and lateral amplitude of the chewing movements which should be taken into account for future research. However, these differences were small and affected both samples equally.The authors are grateful to the Spanish Ministry of the Economy and Competitiveness (AGL-2016-75403-R, Spain) and to the Regional Government of Valencia (Project Prometeo 2017/189, Spain) for financial support.Rizo, A.; Jimenez-Pérez, I.; Camacho-García, A.; Fiszman, S.; Pérez-Soriano, P.; Tarrega, A. (2019). Impact of texture TDS and flavour TDS tasks and of chocolate-chip biscuit characteristics on oral processing features. Food Quality and Preference. 76:109-117. https://doi.org/10.1016/j.foodqual.2019.04.005S1091177

A distance for partially labeled trees

In a number of practical situations, data have structure and the relations among its component parts need to be coded with suitable data models. Trees are usually utilized for representing data for which hierarchical relations can be defined. This is the case in a number of fields like image analysis, natural language processing, protein structure, or music retrieval, to name a few. In those cases, procedures for comparing trees are very relevant. An approximate tree edit distance algorithm has been introduced for working with trees labeled only at the leaves. In this paper, it has been applied to handwritten character recognition, providing accuracies comparable to those by the most comprehensive search method, being as efficient as the fastest.This work is supported by the Spanish Ministry projects DRIMS (TIN2009-14247-C02), and Consolider Ingenio 2010 (MIPRCV, CSD2007-00018), partially supported by EU ERDF and the Pascal Network of Excellence