1,209 research outputs found
Afropean Journeys: A Conversation with E.C. Osondu
No full textNigeria-born and US resident author E.C. Osondu debuted with the short story collection Voice of America (2010), followed by the novel This House is Not for Sale (2015) and Alien Stories (2020). His latest novel, When the Sky is Ready the Stars Will Appear, the compelling tale of an African boy’s journey towards Rome in search of a better life, was first published in translation in Italy with the title Quando il cielo vuole spuntano le stelle (2020). Only one year later, the original version of the novel was published in Nigeria. This piece, based on a conversation with the author within the context of the “Afropean Bridges” 2021 Series, introduces E.C. Osondu and his works to the Italian audience
Ships Observing Marine Climate: a catalogue of the VOS participating in the VSOP-NA
No full textOur present knowledge of the marine climate, as represented by data sets such as COADS (Woodruff et al., 1987), is based on meteorological observations from the Voluntary Observing Ships (VOS). Because the VOS are merchant ships, rather than specially designed meteorological platforms, errors and biases exist in the data. However there is little information readily available to the climatologist either on the nature of the VOS fleet or on the observing practises which are used. This report, describing the forty-six ships that participated in the Voluntary Observing Ships' Special Observing Project - North Atlantic (VSOP-NA), therefore serves two purposes:(i) it provides a reference document to aid analysis of the VSOP-NA data set,(ii) it gives a detailed description of a subset of the VOS, which will be of value in the interpretation of marine climate data sets.This report is in two parts, Part 1 is an overall summary of the ship characteristics, Part 2 is a ship by ship description. The next section will briefly describe the VSOP-NA project, followed by a summary of the characteristics of the VSOP-NA ships (Section 3). Since these ships were specially selected (Section 2.2), the degree to which they are representative of the whole VOS fleet will be carefully considered. The meteorological instrumentation used by the VOS varies depending on which meteorological agency recruited the ships. That used on the chosen VSOP-NA ships is typical of VOS recruited by the countries bordering the North Atlantic, and will be described in Section 4. Section 5 is a summary of Part 1 of the report.Part 2 presents the VSOP-NA ship catalogue. This includes, for each ship, diagrams of the layout (indicating in particular the exposure of the sensors), a summary of the geographical positions at which observations were obtained, and details of the instrumentation used.<br/
Services in Europe: a policy for the '90s. Europe: Magazine of the European Community No. 263, January-February 1987
No full textA comparison of data-driven internal multiple elimination strategies and their consequences for imaging
No full textWe compare two data-driven internal multiple reflection elimination schemes derived from regular Marchenko equations and Inverse Scattering Series (ISS). The scheme derived from regular Marchenko equations creates a new data set without internal multiple reflections. The scheme derived from ISS is equal to the result after the second iteration of the Marchenko-based scheme. It can attenuate internal multiple reflections with residuals. We evaluate the success of two schemes with a 2D complex numerical example. It is shown that Marchenko-based data-driven scheme is relatively more robust for internal multiple reflection elimination.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Applied Geophysics and Petrophysic
Análisis de las dos líneas de transmisión del tratado de Tudmīr (94 H./713 e.C.)
No full textThe two main texts of the transmission lines of the treaty of Tudmīr (94 H/713 e.C. ), included by al- ‘Uḏrī and al-Ḍabbī in their respective works, are edited and translated on the basis of an new reading of the manuscripts that contain them, and after that, we reach some conclusions about its process of copy. There are compared the two texts, and are listed its textual differences. As conclusion, we propose that Al- ‘Uḏrī’s text is the oldest, because its author has copied them from the original document of the 8th. c. (or a copy transfer of this). The transmission of al-Ḍabbī is more recent and it was based in an oral transmission of the text.Análisis de las dos líneas de transmisión del tratado de Tudmīr (94 H./713 e.C.)Los dos textos principales de las líneas de transmisión del tratado de Tudmīr (94 H/713 e.C.), incluidos por al-‘Uḏrī y al-Ḍabbī en sus respectivas obras, son editados y traducidos en base a la relectura de los manuscritos que los contienen y de ello se extraen una serie de conclusiones sobre su proceso de copia. Luego son comparados los dos textos entre sí y se enumeran una serie de diferencias textuales. Finalmente, como hipótesis interpretativa se propone que el texto de al-‘Uḏrī es el más antiguo, y habría sido copiado de un traslado del original por su autor, mientras que la transmisión de al-Ḍabbī habría sido más reciente y se habría fundado en otra fuente más antigua que habría puesto por escrito un relato oral del texto
A study of phytochrome, its isolation, structure and photochemical transformations
No full textApplied Science
Cosmos: a sketch of a physical description of the universe
No full textRetrieved from "Biodiversity Heritage Library" Translated from the German by E.C. Otte. New York: Harper & Brothers - 1877 TRANSLATOR'S PREFACE I CAN not more appropriately introduce the Cosmos than by presenting a brief sketch of the life of its illustrious author.* While the name of Alexander von Humboldt is familiar to every one, few, perhaps, are aware of the peculiar circumstances of his scientific career and of the extent of his labors in almost every department of physical knowledge. He was born on the 14th'' of September, 1769, and is, therefore, now in his 80 th year. After going through the ordinary course of education at Gottingen, and having made a rapid tour through Holland, England; and France, he became a pupil of Werner at the mining school of Freyburg, and in his 21st year published an "Essay on the Basalts of the Rhine." Though he soon became officially connected with the mining corps, he was enabled to continue his excursions in foreign countries, for, during the six or seven years succeeding the publication of his first essay, he seems to have visited Austria, Switzerland, Italy, and France. His attention to mining did not, however, prevent him from devotmg his attention to other scientific pursuits, among which botany and the then recent discovery of galvanism may be especially noticed. Botany, indeed, we know from his own authority, occupied him almost exclusively for some years ; but even at this time he was practicing the use of those astronomical and physical instruments which he afterward turned to so singularly excellent an account
Electric characterization of construction materials through radar data inversion
No full textThe non-destructive evaluation with the aim of characterizing objects before or after treatment has taken place, and the monitoring of long-term performance is analyzed in this thesis. Generally, these test methods measure material properties or changes in these properties that decision makers are interested in. There is a variety of non-destructive testing (NDT) methods to choose from, depending on the aim of the analysis. Generally speaking, different non-destructive testing methods can be used for investigating the inner structure of materials. It is worth noticing that there is not one single analytical method able to provide all the necessary information. Therefore, a combined test series capable of providing complementary information is usually adopted. Most of the methods used in NDT generate pictures of the object interior that can help locate structural flaws. Even though not common, these methods can give quantitative results. The use of electromagnetic waves within the radio frequency bandwidth, in particular, can be valuable in detecting defects, for assessing the deterioration and the success of refurbishment activities. A particular radar technology was used in this study as a tool for assessing the ability to characterize materials in specific built environments. Numerical and laboratory studies were carried out to evaluate the feasibility of the proposed methodology for the mentioned applications. A secondary objective was to provide a contribution to the road safety, preventing the risk of severe damage of pavement, induced by clay content in sub-asphalt layers, and to improve the operations of rehabilitation and maintenance through an effective inspection. In Chapter 2 the electric properties of multiphase aggregate mixtures were evaluated for a given mineralogic composition at frequencies between 300 kHz and 3 GHz. Two measurement techniques were employed: a coaxial transmission line and a monostatic stepped-frequency ground-penetrating radar. The propagation matrices analytical method was used to retrieve the electrical permittivity and conductivity of the mixtures from the measured scattering parameters in the coaxial transmission line. The effect of increasing water content was analyzed in several sand-clay mixtures. For the end-member case of maximum clay (25% by weight) and increasing water content, investigations were compared between the two measurement techniques. The electrical properties of materials are influenced by the amount of water, but clay affects the frequency dependency of soils showing distinctive features regardless of the mineralogy. The microwave attenuation, expressed by the quality factor Q, is partly dependent on frequency and on water content. The performance of one empirical and one volumetric mixing model was evaluated to assess the capability of indirectly retrieving the volumetric water content for a known mixture. The results obtained were encouraging for applications in the field of pavement engineering with the aim of clay detection. The models used show similar behaviors, but measured data were better modeled using third order polynomial equations. High-frequency, ultra-wideband penetrating radar has the potential to be used as a non-invasive inspection technique for buildings, providing high-resolution images of structures and possible fractures affecting constructions. To test this possibility, in Chapter 3 numerical and laboratory experiments were conducted using a proximal, stepped-frequency continuous-wave radar system operating in zero-offset mode, spanning the 3-8 GHz frequency range. The reconstruction of material electrical properties is achieved by resorting to full-waveform inverse modeling. Numerical experiments showed that for typical electric permittivity and electrical conductivity values of concrete and plaster, it is possible to retrieve the physical properties of the material and to detect fractures less than 1 mm thick. Laboratory experiments were conducted on non-reinforced concrete and plaster test slabs in different configurations. The results showed the good potential of this method: (1) to provide a thorough fracture response model in buildings or artworks and (2) to non-invasively characterize the samples in terms of their electromagnetic properties. The characterization of the subsurface can be performed by full-waveform inversion of electromagnetic data relating to a particular model. The modeling process relies on the ability of retrieving the scattered field Green’s function from the measured data. This is achieved using sets of antenna characteristic global reflection and transmission coefficients to describe the media in terms of their scattered field impulse response. As described in Chapter 4, crucial for a successful implementation of this technique is the understanding of uncertainties involved in the acquisition of the antenna calibration and survey measurements, and how these propagate in the parameter estimation results. It was found that averaging a number of possible Green’s functions obtained from one measurement with several antenna characteristic coefficients sets works remarkably well in reducing the uncertainties. The accuracy of the inversions improved using characteristic coefficients acquired as close as possible to the measurement conditions. Moreover, a clear relation between dynamic range and system resolution was highlighted, based on the number of effective bits contained in the data. The presence of cohesive soils as bearing courses of road pavement frequently causes damages and defects (e.g., transversal and longitudinal cracks, deformations and ruts). In Appendix A, different ground-penetrating radar (GPR) methods and techniques were used to non-destructively investigate the clay content in sub-asphalt compacted soils. The experimental layout provided the use of typical road materials, employed for road bearing courses construction. Three types of soils classified as A1, A2, A3 by the American Association of State Highway and Transportation Officials (AASHTO) were used and adequately compacted in electrically and hydraulically isolated test boxes. Analyses were carried out for each clay content using two different GPR instruments. A pulse radar with ground-coupled antennae at 500 MHz center frequency and a vector network analyzer (VNA) with a 1–3 GHz bandwidth were used. Signals were processed in both time and frequency domains, and the consistency of results was validated by the Rayleigh scattering method, the full-waveform inversion and the signal picking techniques. Promising results were obtained for the detection of clay content or cohesive soils affecting the bearing capacity of sub-asphalt layers.Geoscience & EngineeringCivil Engineering and Geoscience
Electrical Survey of Peat Deposits
No full textGeoscience & EngineeringCivil Engineering and Geoscience
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