2,636 research outputs found
Il valore metodico del carattere di además
Uno de los temas más importantes del pensamiento de Polo es su
propuesta de ampliación trascendental, que en sus obras se presenta en relación con
lo que llama "carácter de además". Se estudia el significado de esta expresión, especialmente
de su valor metódico para el conocimiento de la persona. Como Polo
habla, en antropología, de "solidaridad metódico-temática" se dedica cierta atención a
la dimensión temática, pero con el objetivo principal de aclarar la metódica, que Polo
llama también "hábito de sabiduría"
A Biased Resistor Network Model for Electromigration Failure and Related Phenomena in Metallic Lines
Electromigration phenomena in metallic lines are studied by using a biased
resistor network model. The void formation induced by the electron wind is
simulated by a stochastic process of resistor breaking, while the growth of
mechanical stress inside the line is described by an antagonist process of
recovery of the broken resistors. The model accounts for the existence of
temperature gradients due to current crowding and Joule heating. Alloying
effects are also accounted for. Monte Carlo simulations allow the study within
a unified theoretical framework of a variety of relevant features related to
the electromigration. The predictions of the model are in excellent agreement
with the experiments and in particular with the degradation towards electrical
breakdown of stressed Al-Cu thin metallic lines. Detailed investigations refer
to the damage pattern, the distribution of the times to failure (TTFs), the
generalized Black's law, the time evolution of the resistance, including the
early-stage change due to alloying effects and the electromigration saturation
appearing at low current densities or for short line lengths. The dependence of
the TTFs on the length and width of the metallic line is also well reproduced.
Finally, the model successfully describes the resistance noise properties under
steady state conditions.Comment: 39 pages + 17 figure
FROM THE GENERAL DOCUMENTATION OF HADRIAN'S VILLA TO DESIGN ANALYSIS OF COMPLEX CUPOLAS: A PROCEDURAL APPROACH
Abstract. The paper illustrates the progress of Hadrian's Villa digital documentation with special emphasis on a series of modelling issues emerged while studying vaults and cupolas of the site. Together with the more general problem of giving scientific coherence to both active and passive sensor outputs – systematically gathered from 2013 – a methodological problem concerning data interpretation of complex opus caementicium vaults have become dramatically important for the interdisciplinary research team. A methodology for improving the understanding the original shapes of Hadrianic cupolas was designed to provide scholars and professionals operating at the Villa with reliable and easy to use outputs, for interpretation, restoration, maintenance practice. Sensors integration played a fundamental role since allowed researchers a global understanding of intrados and extrados surfaces using reverse modelling applications. Features and 2D primitives extracted from high-resolution models were analysed in order to create flexible procedural models of reconstruction hypothesis/completion of cupolas. Due to the very nature of these shapes (apparently irregular), but with a solid geometric conception, we applied the last achievements of Catmull-Clark bicubic surfaces in combination with Visual Programming Language (VPL).</p
Sources of performance improvement in privatised firms: A clinical study of the global telecommunications industry
This paper examines the financial and operating performance of 31 national telecommunication companies in 25 countries that were fully or partially privatised through public share offering between October 1981 and November 1998. Using conventional pre- versus post-privatisation comparisons, we find that profitability, output, operating efficiency and capital investment spending increase significantly after privatisation, while employment and leverage decline significantly. However, these univariate comparisons do not account for separate regulatory and ownership effects (retained government stake), and almost all telecoms are subjected to material new regulatory regimes around the time they are privatised. We examine these separate effects using both random and fixed-effect panel data estimation techniques for a seven-year period around privatisation. We verify that privatisation is significantly related to higher profitability, output and efficiency, and with significant declines in leverage. However, we also find numerous separable effects for variables measuring regulation, competition, retained government ownership and foreign listing (on U.S. and U.K. exchanges). Competition significantly reduces profitability, employment and, surprisingly, efficiency after privatisation, while creation of an independent regulatory agency significantly increases output. Mandating third party access to an incumbent's network is associated with a significant decrease in the incumbent's investment and an increase in employment. Retained government ownership is associated with a significant increase in leverage and a significant decrease in employment, while price regulation significantly increases profitability. Major efficiency gains result from better incentives and productivity, rather than from wholesale firing of employees and profitability increases appear to be caused by significant reductions in costs—rather than price increases. On balance, we conclude that the financial and operating performance of telecommunications companies improves significantly after privatisation, but that a sizeable fraction of the observed improvement results from regulatory changes—alone or in combination with ownership changes—rather than from privatisation alone
Polar exploration of complex surface germs
We prove that the topological type of a normal surface singularity
pX, 0q provides finite bounds for the multiplicity and polar multiplicity of pX, 0q,
as well as for the combinatorics of the families of generic hyperplane sections
and of polar curves of the generic plane projections of pX, 0q. A key ingredient
in our proof is a topological bound of the growth of the Mather discrepancies
of pX, 0q, which allows us to bound the number of point blowups necessary to
achieve factorization of any resolution of pX, 0q through its Nash transform.
This fits in the program of polar explorations, the quest to determine the generic
polar variety of a singular surface germ, to which the final part of the paper is
devoted
Heron’s Legacy: An Example of Ancient Calculations Applied to Roman Imperial Architecture
Heron of Alexandria is a well-known author in the field of mathematics and engineering,
but his work is of great interest for understanding ancient construction
problems related to architecture. The formulas translated and commented on by
Heiberg (1914a, b) are analyzed through geometric diagrams and applied to famous
Roman domed architecture
Raman excitation spectroscopy of carbon nanotubes: effects of pressure medium and pressure
Raman excitation and emission spectra for the radial breathing mode (RBM) are
reported, together with a preliminary analysis. From the position of the peaks
on the two-dimensional plot of excitation resonance energy against Raman shift,
the chiral indices (m, n) for each peak are identified. Peaks shift from their
positions in air when different pressure media are added - water, hexane,
sulphuric acid - and when the nanotubes are unbundled in water with surfactant
and sonication. The shift is about 2 - 3 cm-1 in RBM frequency, but
unexpectedly large in resonance energy, being spread over up to 100meV for a
given peak. This contrasts with the effect of pressure. The shift of the peaks
of semiconducting nanotubes in water under pressure is orthogonal to the shift
from air to water. This permits the separation of the effects of the pressure
medium and the pressure, and will enable the true pressure coefficients of the
RBM and the other Raman peaks for each (m, n) to be established unambiguously.Comment: 6 pages, 3 Figures, Proceedings of EHPRG 2011 (Paris
Field reliability of GaAs emitters for fiber optic telecommunication systems
GaAs based emitters are widely used in telecommunication systems, and will be probably the core of short haul communications, even if a lot of doubts still exist on their reliability and the few available field results are not too optimistic. For these reasons we decided to follow with a particular attention all the problems related to these devices, investigating reliability by means of accelerated tests and of an accurate survey of field troubles. In this paper, we first of all report our field data, coming from more than five years experience, which show that "reasonable" results (in the range of 2000 FITs for LDs), can be obtained with commercially available devices; as a second step, failure analysis allows to localize failures,thus understanding the appropriate corrective actions to be taken. highlighting the specific process report also same For chip related failures, detailed examples are reported, different failure mechanisms, that, when not related to defects, are the same found during accelerated tests; we examples of failures due to interconnections and packaging
Monitoring of the conservation state of the internal wall surfaces of Room with Golden Vault in the Domus Aurea
This project describes the monitoring campaign, performed in situ with the collaboration of Konica Minolta Sensing Europe, in order to verify the actual conservation state of the internal wall surfaces of the Room with Golden Vault in the Domus Aurea in Rome. Particularly, the main aim of this work was to evaluate the problems caused by aggressive environmental conditions (combination of low air temperature and high relative humidity).
During this survey, characterized by the integrated use of two and three-dimensional techniques, the environmental conditions were carefully monitored.
Reference sample regions of the vault were acquired by means of the 3D laser scanner Konica Minolta Vivid 9i (optical triangulation-based) that allows capturing morphological details of the stucco decorations with a good resolution. Moreover, each detailed scan was supplied with related high resolution images taken by a digital reflex camera Olympus E-510 rigidly connected to the scanner. In Cultural Heritage monitoring applications it is important to integrate the data acquired with different instruments and techniques. Therefore, by this methodological approach, it has been possible to integrate both two and three dimensional data by the projection of the acquired images on the corresponding digital model. In order to complete the cognitive framework of the vault, systematic measures of spectrophotometry by means of the portable spectrophotometer Minolta 2600d were also carried out. The digital data, collected and elaborated by this monitoring campaign, allowed to create a database of morphological information, high resolution digital images, colorimetric values and reflectance curves that may be used in the future as reference data to periodically monitor the conservation state of the surfaces
In vitro and in vivo antitumoral effects of combinations of polyphenols, or polyphenols and anticancer drugs: Perspectives on cancer treatment
Carcinogenesis is a multistep process triggered by genetic alterations that activate different signal transduction pathways and cause the progressive transformation of a normal cell into a cancer cell. Polyphenols, compounds ubiquitously expressed in plants, have anti-inflammatory, antimicrobial, antiviral, anticancer, and immunomodulatory properties, all of which are beneficial to human health. Due to their ability to modulate the activity of multiple targets involved in carcinogenesis through direct interaction or modulation of gene expression, polyphenols can be employed to inhibit the growth of cancer cells. However, the main problem related to the use of polyphenols as anticancer agents is their poor bioavailability, which might hinder the in vivo effects of the single compound. In fact, polyphenols have a poor absorption and biodistribution, but also a fast metabolism and excretion in the human body. The poor bioavailability of a polyphenol will affect the effective dose delivered to cancer cells. One way to counteract this drawback could be combination treatment with different polyphenols or with polyphenols and other anti-cancer drugs, which can lead to more effective antitumor effects than treatment using only one of the compounds. This report reviews current knowledge on the anticancer effects of combinations of polyphenols or polyphenols and anticancer drugs, with a focus on their ability to modulate multiple signaling transduction pathways involved in cancer
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