The use of conventional manufacturing methods is mainly limited by the size of the production run and the geometrical complexity of the component, and as a result we are occasionally forced to use ...processes and tools that increase the final cost of the element being produced. Additive manufacturing techniques provide major competitive advantages due to the fact that they adapt to the geometrical complexity and customised design of the part to be manufactured. The following may also be achieved according to field of application: lighter weight products, multimaterial products, ergonomic products, efficient short production runs, fewer assembly errors and, therefore, lower associated costs, lower tool investment costs, a combination of different manufacturing processes, an optimised use of materials, and a more sustainable manufacturing process. Additive manufacturing is seen as being one of the major revolutionary industrial processes of the next few years. Additive manufacturing has several alternatives ranging from simple RepRap machines to complex fused metal deposition systems. This paper will expand upon the structural design of the machines, their history, classification, the alternatives existing today, materials used and their characteristics, the technology limitations, and also the prospects that are opening up for different technologies both in the professional field of innovation and the academic field of research. It is important to say that the choice of technology is directly dependent on the particular application being planned: first the application and then the technology.
The Central Engines of Fermi Blazars Paliya, Vaidehi S.; Domínguez, A.; Ajello, M. ...
The Astrophysical journal. Supplement series,
04/2021, Letnik:
253, Številka:
2
Journal Article
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Odprti dostop
Abstract
We present a catalog of central engine properties, i.e., black hole mass (
M
BH
) and accretion luminosity (
L
disk
), for a sample of 1077 blazars detected with the Fermi Large Area ...Telescope. This includes broad emission-line systems and blazars whose optical spectra lack emission lines but are dominated by the absorption features arising from the host galaxy. The average
M
BH
for the sample is
, and there is evidence suggesting the association of more massive black holes with absorption-line systems. Our results indicate a bimodality of
L
disk
in Eddington units (
L
disk
/
L
Edd
) with broad-line objects tend to have a higher accretion rate (
L
disk
/
L
Edd
> 0.01). We have found that
L
disk
/
L
Edd
and Compton dominance (CD; the ratio of the inverse Compton to synchrotron peak luminosities) are positively correlated at the >5
σ
confidence level, suggesting that the latter can be used to reveal the state of accretion in blazars. Based on this result, we propose a CD-based classification scheme. Sources with CD > 1 can be classified as high-Compton-dominated or HCD blazars, whereas those with CD ≲ 1 are low-Compton-dominated (LCD) objects. This scheme is analogous to that based on the mass accretion rate proposed in the literature; however, it overcomes the limitation imposed by the difficulty in measuring
L
disk
and
M
BH
for objects with quasi-featureless spectra. We conclude that the overall physical properties of Fermi blazars are likely to be controlled by the accretion rate in Eddington units. The catalog is made public at
http://www.ucm.es/blazars/engines
and Zenodo.
The extragalactic background light (EBL) can be probed via the absorption imprint it leaves in the spectra of gamma-ray sources ( ). We recently developed a dedicated technique to reconstruct the ...EBL, and its evolution with redshift, from γ-ray optical depth data using a large sample of blazars detected by the Fermi Large Area Telescope. Here, we extend this data set to the TeV regime using ground-based Cherenkov observations of 38 blazars and report the first homogeneous measurement of the EBL spectral intensity covering the ultraviolet to infrared wavelengths (∼0.1-100 m). A minimal EBL throughout the wavelength range with respect to integrated galaxy light is found, allowing little additional unresolved emission from faint or truly diffuse populations setting an upper limit of 4 nW m−2 sr−1 at 1.4 m. In particular, the cosmic optical background at z = 0 is found to be . This work lays the foundation for accurate gamma-ray measurements of the EBL across its whole spectral range using a combination of GeV and TeV data.
We present the results of a study of the time-averaged spectral energy distributions (SEDs) of eight flat spectrum radio quasars (FSRQs) present in the second catalog of high energy sources detected ...beyond 50 GeV by the Fermi Large Area Telescope (2FHL). Both leptonic and hadronic scenarios are adopted to explain the multiwavelength SEDs and we find them to be marginally consistent with the 2FHL spectra above 50 GeV. We derive the expected degree of X-ray and γ-ray polarizations both for the average and elevated activity states and note that (i) a hadronic radiative model consistently predicts a higher degree of high energy polarization compared to leptonic ones and (ii) the X-ray polarization degree is higher than the γ-ray polarization in the leptonic scenario, but similar to the γ-ray polarization if the observed radiation is powered by hadronic processes. From the leptonic modeling, the location of the γ-ray emitting region is found to be at the outer edge of the broad line region (BLR) and is consistent with the γγ opacity estimates for the γ-ray absorption by the BLR. We conclude that a majority of the FSRQs could be detected by the upcoming Cherenkov Telescope Array, though future high energy polarimeters will be able to detect them only during elevated activity states, which could provide supportive evidence for the hadronic origin of the X-ray and γ-ray emission.
Metallic objects in close contact and illuminated by light show spectacular enhancements of electromagnetic fields due to excitation of surface plasmons, which have the potential for exploitation in ...ultra sensitive spectroscopy and in nonlinear phenomena. They also play a role in van der Waals forces, heat transfer and non contact friction. The extremes of lengthscales, varying from the micrometre to the subnanometre, challenge direct computational attack. Here we show that transformation optics enables an analytic approach that offers both physical insight and easy access to quantitative analysis. For two metal spheres at various separations we present details of the technique and discuss the optical absorption spectrum, spatial distribution of the modes and the van der Waals forces. PUBLICATION ABSTRACT
This paper investigates the environmental and economic performance of the power production from biogas using Life Cycle Assessment, Life Cycle Costing and Cost Benefit Analysis methodologies. The ...analysis is based on a commercial thermophilic biogas plant located in Spain where is installed a Combined Heat and Power system that produces electricity that is sold to the grid. Power generation has been assumed as the only function of the biogas system, expanding the system boundaries to include the additional function related to the end-of-life management of the biowastes. Thus environmental burdens from the conventional management of residues were calculated separately and subtracted. The base scenario involves using agri-food waste, sewage sludge and pig/cow manure as substrates. This situation is compared against an alternative scenario where the production of synthetic fertilizer is surrogated by the digestate.
The results have shown that the most impacting activities in all impacts categories of power production are primarily attributable to the operation and maintenance of the biogas plant except for water resource depletion and climate change. The avoided emissions associated with the conventional management of pig/cow manure more than offset GHG emissions of the biogas system resulting in a negative impact value of −73.9gCO2eq/kWh in the base case scenario. The normalized results show that local impact categories such as primarily human toxicity, fresh water ecotoxicity and particulate matter are the most significantly affected by the biogas system while global impact categories as climate change and ozone depletion are less severely affected.
The operation and maintenance phase is also shown to be the largest contributor after the life cycle cost analysis, followed by the construction and dismantling of the biogas plant and the profitability of the project is primarily related to the income obtained from the management of the biowastes used as substrates.
•Life cycle assessment, life cycle costing and cost benefit analysis were performed.•Operation and maintenance of the biogas plant are the most impacting activities.•Anaerobic digestion of biowaste results in negative values for climate change.•Income obtained from waste treatment is the main input to the plant profitability.
We report a detailed study of an unidentified gamma-ray source located in the region of the compact stellar cluster NGC 3603. This is a star-forming region (SFR) powered by a massive cluster of OB ...stars. A dedicated analysis of about 10 yr of data from 10 GeV to 1 TeV, provided by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope, yields the detection of a pointlike source at a significance of 9 . The source photon spectrum can be described by a power-law model with a best-fit spectral index of 2.35 0.03. In addition, the analysis of a deep Chandra image in the 0.5-7 keV band reliably rules out an extragalactic origin for the gamma-rays. We also conclude that the broadband spectral energy distribution of the point source can be explained well with both leptonic and hadronic models. No firm evidence of association with any other classes of known gamma-ray emitters is found; therefore, we speculate that 4FGL J1115.1−6118 is a gamma-ray-emitting SFR.
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