46 research outputs found
Revisiting the design intent concept in the context of mechanical CAD education
[EN] Design intent is generally understood simply as a CAD modelÂżs anticipated behavior when altered.
However, this representation provides a simplified view of the modelÂżs construction and purpose,
which may hinder its general understanding and future reusability. Our vision is that design intent
communication may be improved by recognizing the multifaceted nature of design intent, and by
instructing users to convey each facet of design intent through the better-fitted CAD resource. This
paper reviews the current understanding of design intent and its relationship to design rationale and
builds on the idea that communication of design intent conveyed via CAD models can be satisfied
at three levels provided that specialized instruction is used to instruct users in selection of the most
suitable level for each intent.Otey, J.; Company, P.; Contero, M.; Camba, J. (2018). Revisiting the design intent concept in the context of mechanical CAD education. Computer-Aided Design and Applications. 15(1):47-60. https://doi.org/10.1080/16864360.2017.1353733S476015
Suzaku Observations of Luminous Quasars: Revealing the Nature of High-Energy Blazar Emission in Quiescent States
We present the results from the Suzaku X-ray observations of five
flat-spectrum radio quasars (FSRQs), namely PKS0208-512, Q0827+243,
PKS1127-145, PKS1510-089 and 3C 454.3. All these sources were additionally
monitored simultaneously or quasi-simultaneously by the Fermi satellite in
gamma-rays and the Swift UVOT in the UV and optical bands, respectively. We
constructed their broad-band spectra covering the frequency range from 10^14 Hz
up to 10^25 Hz, and those reveal the nature of high-energy emission of luminous
blazars in their low-activity states. The analyzed X-ray spectra are well
fitted by a power-law model with photoelectric absorption. In the case of
PKS0208-512, PKS1127-145, and 3C 454.3, the X-ray continuum showed indication
of hard-ening at low-energies. Moreover, when compared with the previous X-ray
observations, we see a significantly increasing contribution of low-energy
photons to the total X-ray fluxes when the sources are getting fainter. The
same behavior can be noted in the Suzaku data alone. A likely explanation
involves a variable, flat-spectrum component produced via inverse-Compton (IC)
emission, plus an additional, possibly steady soft X-ray component prominent
when the source gets fainter. This soft X-ray excess is represented either by a
steep powerlaw (photon indices Gamma ~ 3 - 5) or a blackbody-type emission with
temperatures kT ~ 0.1-0.2 keV. We model the broad-band spectra spectra of the
five observed FSRQs using synchrotron self-Compton (SSC) and/or
external-Compton radiation (ECR) models. Our modeling suggests that the
difference between the low and high-activity states in luminous blazars is due
to the different total kinetic power of the jet, most likely related to varying
bulk Lorentz factor of the outflow within the blazar emission zone.Comment: 36 pages, 8 figures, 11 tables. Accepted for publication in the
Astrophysical Journal
Fermi/LAT discovery of gamma-ray emission from the flat-spectrum radio quasar PKS 1454-354
We report the discovery by the Large Area Telescope (LAT) onboard the Fermi
Gamma-ray Space Telescope of high-energy gamma-ray (GeV) emission from the
flat-spectrum radio quasar PKS 1454-354 (z=1.424). On 4 September 2008 the
source rose to a peak flux of (3.5 +/- 0.7)x 10^-6 ph cm^-2 s^-1 (E > 100 MeV)
on a time scale of hours and then slowly dropped over the following two days.
No significant spectral changes occurred during the flare. Fermi/LAT
observations also showed that PKS 1454-354 is the most probable counterpart of
the unidentified EGRET source 3EG J1500-3509. Multiwavelength measurements
performed during the following days (7 September with Swift; 6-7 September with
the ground-based optical telescope ATOM; 13 September with the Australia
Telescope Compact Array) resulted in radio, optical, UV and X-ray fluxes
greater than archival data, confirming the activity of PKS 1454-354.Comment: 8 pages, 5 figures, 2 tables. Accepted for publication on ApJ Main
Journa
Taxonomic status and conservation relevance of the raccoons (Procyon spp.) of the West Indies
City for sale: the transformation of San Francisco
San Francisco is perhaps the most exhilarating of all American cities--its beauty, cultural and political avant-gardism, and history are legendary, while its idiosyncrasies make front-page news. In this revised edition of his highly regarded study of San Francisco's economic and political development since the mid-1950s, Chester Hartman gives a detailed account of how the city has been transformed by the expansion--outward and upward--of its downtown. His story is fueled by a wide range of players and an astonishing array of events, from police storming the International Hotel to citizens forcing the midair termination of a freeway. Throughout, Hartman raises a troubling question: can San Francisco's unique qualities survive the changes that have altered the city's skyline, neighborhoods, and economy? Hartman was directly involved in many of the events he chronicles and thus had access to sources that might otherwise have been unavailable. A former activist with the National Housing Law Project, San Franciscans for Affordable Housing, and other neighborhood organizations, he explains how corporate San Francisco obtained the necessary cooperation of city and federal governments in undertaking massive redevelopment. He illustrates the rationale that produced BART, a subway system that serves upper-income suburbs but few of the city's poor neighborhoods, and cites the environmental effects of unrestrained highrise development, such as powerful wind tunnels and lack of sunshine. In describing the struggle to keep housing affordable in San Francisco and the seemingly intractable problem of homelessness, Hartman reveals the human face of the city's economic transformation