1,721,310 research outputs found
Searching for the continuum spectrum photons correlated to the 130 GeV gamma-ray line
No full textIndications for a gamma-ray line(s) signal toward the Galactic Center at an energy of about 130 GeV have been recently presented. While dark matter annihilations are a viable candidate for this signal, it is generally expected that such a flux would be correlated to a gamma-ray component with continuum energy spectrum due to dark matter pair annihilating into other Standard Model particles. We use the gamma-ray data from the inner 10 degrees x 10 degrees window to derive limits for a variety of dark matter annihilation final states. Extending the window of observation, we discuss bounds on the morphological shape of a dark matter signal associated to the line, applying both standard templates for the dark matter profile, such as an Einasto or a Navarro-Frenk-White profile, and introducing a new more general parametrization
Investigation of entropy generation, PEC, and efficiency of parabolic solar collector containing water/Al2O3?MWCNT hybrid nanofluid in the presence of finned and perforated twisted tape turbulators using a two-phase flow scheme
No full textRenewable energy is a type of convenient energy obtained from renewable sources, which can be replaced naturally again on the human time scale. One of the most broadly employed types of renewable energy is solar energy. In the present study, the entropy generation, performance evaluation criterion (PEC), and efficiency of parabolic solar collector containing water/Al2O3_MWCNT hybrid nanofluid are numerically examined in the presence of finned and perforated twisted tape turbulators by employing two-phase flow approach. The volume fraction of nanoparticles (phi) changes from 0 to 3% and the Reynolds number (Re) range is 5000-35,000. The two-phase Eulerian-Eulerian model (EEM), k-omega turbulence model, finite volume method (FVM) method, and SIMPLEC algorithm are used for numerical simulations. The results demonstrate that the maximum change in the total entropy generation is 40.07% by changing the type of turbulator from a perforated tape to the finned vane turbulator which occurs at Re = 30,000 and phi= 3%. The maximum change in the collector efficiency is 1.62% by changing the type of turbulator from finned turbulator to perforated tape one which occurs at Re = 20,000 and phi = 0%. The maximum change in ANU is 13.65%, which occurs at Re = 15,000 and phi = 1%.It is more desirable to use the perforated twisted tape from the point of view of heat transfer, total entropy generation, PEC, and collector efficiency
Performance evaluation criteria and entropy generation of hybrid nanofluid in a shell-and-tube heat exchanger with two different types of cross-sectional baffles
No full textImproving the thermo-hydraulic performance of shell-and-tube heat exchangers is of interest to researchers due to their broad applications in the industry. Thermo-hydraulic behavior and entropy generation of hybrid nanofluid in a shell-and-tube heat exchanger with two different types of cross-sectional baffles are numerically examined using the two-phase Eulerian-Eulerian Model (EEM). The volume fraction of nanoparticles (phi) changes from 0 to 2% and the Reynolds number (ReNumber) varies from 25000 to 45000. EEM, Realizable k-epsilon turbulence model, finite volume method (FVM), and SIMPLE algorithm are used for modeling. According to the numerical results obtained in terms of pressure drop, total entropy generation, and performance evaluation criteria (PEC), baffle 1 is more appropriate. In terms of heat transfer rate and average Nusselt number values, baffle 2 is more suitable. The PEC maximum change was 5.13% at Re = 45000 and phi = 0% by changing the type of baffle from the second type to the first type. The maximum rise in the total entropy generation was 73.68% for phi = 0% for the first type of baffles
FIGURE 4. Isocolus beheni n in New species of herb gallwasps from the Middle East (Hymenoptera, Cynipidae, Aylacini)
No full textFIGURE 4. Isocolus beheni n. sp.: a, head (front view); b, head (dorsal view); c, antenna, female; d, pronotum (dorsal view); e, mesosoma (lateral view); f, mesoscutum and mesoscutellum (dorsal view); g, propodeum (postero-dorsal view); h, forewing; i, metasoma (lateral view).Published as part of Karimpour, Y., Tavakoli, M. & Melika, G., 2008, New species of herb gallwasps from the Middle East (Hymenoptera, Cynipidae, Aylacini), pp. 16-32 in Zootaxa 1854 (1) on page 25, DOI: 10.11646/zootaxa.1854.1.2, http://zenodo.org/record/513308
FIGURE 7. Isocolus karimpouri n in New species of herb gallwasps from the Middle East (Hymenoptera, Cynipidae, Aylacini)
No full textFIGURE 7. Isocolus karimpouri n. sp., galls: a, larval chamber, close–up; b, last instar gallwasp larva (photo by Y. Karimpour); c, larval chamber with emerging hole (longitudinal dissection of the stem) (photos by G. Melika).Published as part of Karimpour, Y., Tavakoli, M. & Melika, G., 2008, New species of herb gallwasps from the Middle East (Hymenoptera, Cynipidae, Aylacini), pp. 16-32 in Zootaxa 1854 (1) on page 31, DOI: 10.11646/zootaxa.1854.1.2, http://zenodo.org/record/513308
Reorganising healthcare delivering in hospital: structure and processes to serve quality
No full textDiscussion about the emerging trends in hospital reorganisation toward departmental structure and multidisciplinary work. Management and governance issue are investigated
FIGURE 6. Isocolus karimpouri n in New species of herb gallwasps from the Middle East (Hymenoptera, Cynipidae, Aylacini)
No full textFIGURE 6. Isocolus karimpouri n. sp.: a, head (front view); b, head (dorsal view); c, antenna, female; d: antenna, male; e: pronotum (dorsal view); f, mesoscutum and mesoscutellum (dorsal view); g, mesosoma (lateral view); h, propodeum (postero-dorsal view); i, forewing; j, metasoma (lateral view).Published as part of Karimpour, Y., Tavakoli, M. & Melika, G., 2008, New species of herb gallwasps from the Middle East (Hymenoptera, Cynipidae, Aylacini), pp. 16-32 in Zootaxa 1854 (1) on page 29, DOI: 10.11646/zootaxa.1854.1.2, http://zenodo.org/record/513308
Diffuse Galactic Gamma Rays at intermediate and high latitudes. I. Constraints on the ISM properties
No full textWe study the high latitude (vertical bar b vertical bar > 10 degrees) diffuse gamma-ray emission in the Galaxy in light of the recently published data from the Fermi collaboration at energies between 100MeV and 100GeV. The unprecedented accuracy in these measurements allows to probe and constrain the properties of sources and propagation of cosmic rays (CRs) in the Galaxy, as well as confirming conventional assumptions made on the interstellar medium (ISM). Using the publicly available DRAGON code, that has been shown to reproduce local measurements of CRs, we study assumptions made in the literature on atomic (HI) and molecular hydrogen (H2) gas distributions in the ISM, and non spatially uniform models of diffusion in the Galaxy. By performing a combined analysis of CR and gamma-ray spectra, we derive constraints on the properties of the ISM gas distribution and the vertical scale height of galactic CR diffusion, which may have implications also on indirect Dark Matter detection. We also discuss some of the possible interpretations of the break at high rigidity in CR protons and helium spectra, recently observed by P A M E L A and their impact on gamma-rays
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