4,278 research outputs found
On the astronomical origin of the Hallstatt oscillation found in radiocarbon and climate records throughout the Holocene
An oscillation with a period of about 2100-2500 years, the Hallstatt cycle,
is found in cosmogenic radioisotopes (C-14 and Be-10) and in paleoclimate
records throughout the Holocene. Herein we demonstrate the astronomical origin
of this cycle. Namely, this oscillation is coherent to the major stable
resonance involving the four Jovian planets - Jupiter, Saturn, Uranus and
Neptune - whose period is p=2318 yr. The Hallstatt cycle could derive from the
rhythmic variation of the circularity of the solar system disk assuming that
this dynamics could eventually modulate the solar wind and, consequently, the
incoming cosmic ray flux and/or the interplanetary/cosmic dust concentration
around the Earth-Moon system. The orbit of the planetary mass center (PMC)
relative to the Sun is used as a proxy. We analyzed how the instantaneous
eccentricity vector of this virtual orbit varies from 13,000 B. C. to 17,000 A.
D.. We found that it undergoes kind of pulsations as it clearly presents
rhythmic contraction and expansion patterns with a 2318 yr period together with
a number of already known faster oscillations associated to the planetary
orbital stable resonances. We found that a fast expansion of the Sun-PMC orbit
followed by a slow contraction appears to prevent cosmic rays to enter within
the system inner region while a slow expansion followed by a fast contraction
favors it. Similarly, the same dynamics could modulate the amount of
interplanetary/cosmic dust falling on Earth. These would then cause both the
radionucleotide production and climate change by means of a cloud/albedo
modulation. Other stable orbital resonance frequencies (e.g. at periods of 20
yr, 45 yr, 60 yr, 85 yr, 159-171-185 yr, etc.) are found in radionucleotide,
solar, aurora and climate records, as determined in the scientific literature.
Thus, the result supports a planetary theory of solar and/or climate variation.Comment: 36 pages, 14 figures, 1 tabl
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Infrared spectroscopic analysis of water incorporated in the structure of industrial soda-lime-silica glasses
The paper illustrates a method for the determination of the water content of glasses by infrared transmittance spectroscopy from the exdnctions of the bands due to free and hydrogen-bonded hydroxyl groups dissolved in the glass. The procedure is discussed in detail, highlighting the sources of random and systematic errors and what can be done to improve the interlaboratory reproducibihty. The ratio of the intensities of the two bands at 2.8 and 3.6 ”m is investigated accurately for a range of industrial soda-lime-silica glasses. In the case of containers and float glass it is nearly constant, but it varies widely for other products, such as household appliances, car headlamps and hand worked arĂŒcles, probably due to differences in the glass formulation. Accordingly, caution should be exerted in using the simplified method based on the measurement of the first band only, implying a constant rado. Finally, evidence of molecular water in the dealkalized surface layers of commercial articles is obtained using infrared reflectance spectroscopy
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Study of the high-temperature spectral behavior of container glass
The spectral absorption coefficients of container glasses in the wavelength region from 0.4 to 4.5 ”m and in the temperature range from room temperature to 1400 °C were measured by a single-beam spectrophotometer by means of the transmission method. From the measured absorption coefficients radiative thermal conductivities in the temperature rÀnge from 600 to 1400 °C were calculated by means of Rosseland's diffusion approximation. The intensity of the band at 2.8 ”m due to dissolved hydroxyl groups in glass was also calculated. While most previous measurements were performed on model glasses with a very simple basic composition, molten in laboratory furnaces from pure raw materials, the glasses investigated in this paper are the most frequently used types of container glasses with a complex composition and different chromophores. The influence of different coloring agents and dissolved water on the spectral behavior and radiative thermal conductivity of glass were studied, checking how the spectra change from room temperature to high temperature
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Recommended procedure for the IR spectroscopic determination of water in soda-lime-silica glass : Report of the International Commission on Glass (ICG) Technical Committee 14 "Gases in Glass"
The paper illustrates a procedure recommended by Technical Committee 14 (TC14 "Gases in Glass") of the International Commission on Glass (ICG) for the determination of the water content of soda-lime-silica glass by infrared transmittance spectroscopy, based on the two bands at 2.8 and 3.6 Όm using as extincdon coefficients 70 and 150 l/(mol · cm), respectively As shown by the result of two intercomparisons, the agreement on the determined water concentration values can be quite satisfactory, within ±20 ppm, provided the procedure to evaluate the spectral curves is closely specified. The selected extinction coefficients are in reasonable agreement with recent evidence obtained using Nuclear Reaction Analysis
A multi-stage GAN for multi-organ chest X-ray image generation and segmentation
Multi-organ segmentation of X-ray images is of fundamental importance for
computer aided diagnosis systems. However, the most advanced semantic
segmentation methods rely on deep learning and require a huge amount of labeled
images, which are rarely available due to both the high cost of human resources
and the time required for labeling. In this paper, we present a novel
multi-stage generation algorithm based on Generative Adversarial Networks
(GANs) that can produce synthetic images along with their semantic labels and
can be used for data augmentation. The main feature of the method is that,
unlike other approaches, generation occurs in several stages, which simplifies
the procedure and allows it to be used on very small datasets. The method has
been evaluated on the segmentation of chest radiographic images, showing
promising results. The multistage approach achieves state-of-the-art and, when
very few images are used to train the GANs, outperforms the corresponding
single-stage approach
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Angular emissivity at room temperature and spectral reflectance at near normal incidence of float glass, borosilicate glass and glass-ceramics
An accurate investigation of the emissivity of uncoated flat glass (necessary to calculate the solar factor and the U value of glazing according to standardized procedures) was performed in agreement with Groupement Europeen des Producteurs de Verre Fiat, in support of CEN and ISO standardization activities. The total angular emissivity of a range of uncoated float glass samples was determined between 10 and 80 °C with an uncertainty of 0.5%. Both the normal and the hemispherical emissivity were nearly identical for all the samples investigated. No significant differences between the top and the bottom side were observed. Measurements were also extended to borosilicate glass and glass-ceramic plates used for fire-resistant glazing, determining their thermal conductivity and angular emissivity behaviour. In order to obtain addidonal information, also the spectral reflectance curves at near normal incidence between 2000 and 200 c m â»Âč were obtained using a spectroradiometer. The fact that almost identical curves were obtained for a wide range of float glasses (both sides) as well as for the fire-resistant materials confirms the correctness of the close emissivity values found. On the basis of the resuhs obtained, a Standard value of Δn = 0.900 and a Δh/Δn ratio = 0.936 is suggested for both float glass and for the two other materials
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Influence of alumina content and modifiers on phase separation in soda-lime-silica glass
The phase Separation behaviour of industrial soda-lime-silica glass is studied by visible light scattering. The main aspects which differentiate industrial glass from the ternary glass (composition in wt%): 76 SiOâ, 13 NaâO, 11 CaO are considered. The obtained results show that the simple ternary glass easily develops phase Separation upon annealing at suitable temperature levels. Conversely, Container glass is stabilized against demixtion by the presence of a significant AIâOâ concentration, a significantly lower SiOâ content and a more complex chemical formulation (partial Substitution of SiOâ, NaâO and CaO with AIâOâ, KâO and MgO, respectively, as well as minor ingredients)
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