7,364 research outputs found
Productos de alfarería de Cerro Macareno, Sevilla : naturaleza y procedencia de las ánforas y otros objetos cerámicos. Siglos VIII al III a. J.C.
Son muchos los métodos empleados para el estudio de las arcillas y de los productos cerámicos, contribuyendo de distinta manera, aunque complementaria, en el conocimiento
de la composición, procedencia de los materiales, tecnología empleada en su
elaboración y en general en todos aquellos procesos que se pudieron seguir en la tibricación
del objeto cerámico.
Estos métodos pueden ser, bien destructivos, aunque utilizando cantidades muy pequeñas
de muestra, o bien no destructivos, cada vez más empleados en la investigación
moderna.
En el estudio de los materiales cerámicos, bien sea el soporte, o bien sea la pintura
que ha servido para decorarlo, se emplea el análisisq\límico tradicional cualitativo y
cuantitativo. Para este último se emplea cada \leimás la técnica de la absorción atómica.
Asimismo, se emplean los siguientes métodos de análisis por vía física:
La espectroscopía de emisión en el ultravioleta, que permite obtener un espectro
de emisión en el que la parte más frecuentemente utilizada se sitúa entre 200 y 400 nm
(ultravioleta).
La espectrometría de fluorescencia de rayos X es una técnica desde hace tiempo
utilizada. El método tiene poca sensibilidad para elementos tales como el cobre, níquel,
cinc o hierro, a causa del «ruido de fondo» que el mismo aparato emite.
La microfluorescencia permite operar directamente sobre una capa de pintura y su
análisis no es destructivo.
La microsonda electrónica es una aplicación de los principios y de la técnica de la
espectrografía de emisión de rayos X. Su poder separador es infinitamente superior al
del mejor instrumento óptico.
La activación por neutrones, que precisa de una fuente generadora de estas radiaciones
(pila atómica), es, por tanto, de muy difícil empleo. En España se utiliza la pila
atómica de la Junta de Energía Nuclear. Este análisis permite determinar los elementos
mayores, menores y trazas existentes en los objetos cerámicos y en los pigmentos. Es
de un gran interés para conocer la procedencia de los materiales empleados, detectando
el posible o posibles yacimientos de las arcillas utilizadas.
La difracción de rayos X determina la estructura cristalina de los elementos y compuestos
químicos ya sean orgánicos o inorgánicos, si bien la técnica no es válida para
los compuestos amorfos.
Para el estudio de aquellos materiales en los que la pintura se encuentre unida al
soporte mediante lacas, gomas o barnices se emplean métodos de absorción en el infrarrojo,
así como la cromatografía en fase gaseosa.
Los métodos seguidos que se enumeran en el siguiente apartado nos han permitido
identificar la procedencia y naturaleza de las arcillas utilizadas en los objetos cerámicos
objeto de este estudio.Peer reviewe
Materias primas y datos tecnológicos de piezas cerámicas antiguas del yacimiento arqueológico de Cerro Macareno (Sevilla)
14 páginas, 5 figuras, 7 tablas, 7 referencias.[EN]: A study of twenty eight fragments of amphoras from the archaeological bed of Cerro Macareno
(Sevilla) has been done by chemical, physicochemical, X-ray diffraction and thermal methods, in order to
establish the nature and provenance of the raw materials and the technological aspects of their fabrication.
All the data lead to the conclusion that four of the pieces were probably imported from the
Palestine-Phoenicie; the rest were made out of raw materials from the surrounding areas of Cerro
Macareno. Most of the pieces were fired below 700°C, only four of them at about 700-750°C, and the
other seven, probably from 800-850°C.[ES]: Se estudian la composición química y mineralógica, contenido en determinados elementos escasos, materias primas y temperaturas probables de cocción empleadas en la fabricación de un conjunto de 25 fragmentos de ánforas del yacimiento arqueológico de Cerro Macareno (Sevilla). Los métodos empleados fueron análisis químico, difracción de rayos-X, A.T.D., análisis por activación neutrónica y pruebas de cocción intermitente por calentamiento de cien en cien grados, desde 400° a 1.100° C seguido en cada caso de estudios por difracción de rayos-X y de observación de los cambios de color y aspecto de los cortes de las piezas. De todo ello se concluye que cuatro de las piezas estudiadas son de origen importado (Palesti-na-Fenicia), estando fabricadas las restantes con materiales procedentes de los aluviones del Guadalquivir, en las inmediaciones del Cerro Macareno. Del total de las piezas, 17 se cocieron probablemente a temperaturas inferiores a 700°C, cuatro a 700-750° C y siete a 800-850°C.Peer reviewe
Thermal diagnostic of the Optical Window on board LISA Pathfinder
Vacuum conditions inside the LTP Gravitational Reference Sensor must comply
with rather demanding requirements. The Optical Window (OW) is an interface
which seals the vacuum enclosure and, at the same time, lets the laser beam go
through for interferometric Metrology with the test masses. The OW is a
plane-parallel plate clamped in a Titanium flange, and is considerably
sensitive to thermal and stress fluctuations. It is critical for the required
precision measurements, hence its temperature will be carefully monitored in
flight. This paper reports on the results of a series of OW characterisation
laboratory runs, intended to study its response to selected thermal signals, as
well as their fit to numerical models, and the meaning of the latter. We find
that a single pole ARMA transfer function provides a consistent approximation
to the OW response to thermal excitations, and derive a relationship with the
physical processes taking place in the OW. We also show how system noise
reduction can be accomplished by means of that transfer function.Comment: 20 pages, 14 figures; accepted for publication in Class. Quantum Gra
The Bench Press Grip Width Does Not Affect the Number of Repetitions Performed at Different Velocity Loss Thresholds
Institutional Review Board Statement: The study was conducted according to the guidelines of the
Declaration of Helsinki, and approved by the University of Granada Institutional Review Board
(approval: 491/CEIH/2018).We would like to thank all the authors who participated in the data collection.This study aimed (I) to compare the number of repetitions that can be completed to failure (XRM) and before reaching a 15%, 30%, or 45% velocity loss threshold (XVLT) in the bench press exercise performed using different grip widths, and (II) to examine the inter-individual variability in the percentage of completed repetitions with respect to the XRM when the set volume is prescribed based on a fixed number of repetitions (FNR) and several velocity loss thresholds (VLT). Nineteen men performed four separate sessions in a random order where there was a single set of repetitions completed to failure against 75% of the one-repetition maximum during the Smith machine bench press exercise using a narrow, medium, wide, or self-selected grip widths. The XRM (p = 0.545) and XVLTs (p ≥ 0.682) were not significantly affected by grip width. A high and comparable inter-individual variability in the percentage of completed repetitions with respect to the XRM was observed when using both an FNR (median CV = 24.3%) and VLTs (median CV = 23.5%). These results indicate that Smith machine bench press training volume is not influenced by the grip width and that VLTs do not allow a more homogeneous prescription of the set volume with respect to the XRM than the traditional FNR
The bench press grip width does not affect the number of repetitions performed at different velocity loss thresholds
© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This study aimed (I) to compare the number of repetitions that can be completed to failure (XRM) and before reaching a 15%, 30%, or 45% velocity loss threshold (XVLT) in the bench press exercise performed using different grip widths, and (II) to examine the inter-individual variability in the percentage of completed repetitions with respect to the XRM when the set volume is prescribed based on a fixed number of repetitions (FNR) and several velocity loss thresholds (VLT). Nineteen men performed four separate sessions in a random order where there was a single set of repetitions completed to failure against 75% of the one-repetition maximum during the Smith machine bench press exercise using a narrow, medium, wide, or self-selected grip widths. The XRM (p = 0.545) and XVLTs (p ≥ 0.682) were not significantly affected by grip width. A high and comparable inter-individual variability in the percentage of completed repetitions with respect to the XRM was observed when using both an FNR (median CV = 24.3%) and VLTs (median CV = 23.5%). These results indicate that Smith machine bench press training volume is not influenced by the grip width and that VLTs do not allow a more homogeneous prescription of the set volume with respect to the XRM than the traditional FNR
Anharmonic double-phonon excitations in the interacting boson model
Double- vibrations in deformed nuclei are analyzed in the context of
the interacting boson model. A simple extension of the original version of the
model towards higher-order interactions is required to explain the observed
anharmonicities of nuclear vibrations. The influence of three- and four-body
interactions on the moments of inertia of ground- and -bands, and on
the relative position of single- and double- bands is studied
in detail. As an example of a realistic calculation, spectra and transitions of
the highly -anharmonic nuclei Dy, Er, and Er
are interpreted in this approach.Comment: 38 pages, TeX (ReVTeX). 15 ps figures. Submitted to Phys. Rev.
On the relation between models and the interacting boson model
The connections between the models (the original E(5) using an
infinite square well, , and ), based
on particular solutions of the geometrical Bohr Hamiltonian with
-unstable potentials, and the interacting boson model (IBM) are
explored. For that purpose, the general IBM Hamiltonian for the
transition line is used and a numerical fit to the different models
energies is performed, later on the obtained wavefunctions are used to
calculate B(E2) transition rates. It is shown that within the IBM one can
reproduce very well all these models. The agreement is the best for
and reduces when passing through ,
and E(5), where the worst agreement is obtained (although still very good for a
restricted set of lowest lying states). The fitted IBM Hamiltonians correspond
to energy surfaces close to those expected for the critical point. A phenomenon
similar to the quasidynamical symmetry is observed
Towards a cloud‑based automated surveillance system using wireless technologies
Cloud Computing can bring multiple benefits for Smart Cities. It permits the easy creation of centralized knowledge bases, thus straightforwardly enabling that multiple embedded systems (such as sensor or control devices) can have a collaborative, shared intelligence. In addition to this, thanks to its vast computing power, complex tasks can be done over low-spec devices just by offloading computation to the cloud, with the additional advantage of saving energy. In this work, cloud’s capabilities are exploited to implement and test a cloud-based surveillance system. Using a shared, 3D symbolic world model, different devices have a complete knowledge of all the elements, people and intruders in a certain open area or inside a building. The implementation of a volumetric, 3D, object-oriented, cloud-based world model (including semantic information) is novel as far as we know. Very simple devices (orange Pi) can send RGBD streams (using kinect cameras) to the cloud, where all the processing is distributed and done thanks to its inherent scalability. A proof-of-concept experiment is done in this paper in a testing lab with multiple cameras connected to the cloud with 802.11ac wireless technology. Our results show that this kind of surveillance system is possible currently, and that trends indicate that it can be improved at a short term to produce high performance vigilance system using low-speed devices. In addition, this proof-of-concept claims that many interesting opportunities and challenges arise, for example, when mobile watch robots and fixed cameras would act as a team for carrying out complex collaborative surveillance strategies.Ministerio de Economía y Competitividad TEC2016-77785-PJunta de Andalucía P12-TIC-130
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