2,166 research outputs found
Prediction of Low-Voltage Tetrafluoromethane Emissions Based on the Operating Conditions of an Aluminium Electrolysis Cell
Greenhouse gas (GHG) generation is inherent in the production of aluminium by a technology that uses carbon anodes. Most of those GHG are composed of CO2 produced by redox reaction that occurs in the cell. However, a significant fraction of the annual GHG production is composed of perfluorocarbons (PFC) resulting from anode effects (AE). Multiple investigations have shown that
tetrafluoromethane (CF4) can be generated under low-voltage conditions in the electrolysis cells, without global anode effect. The aim of this paper is to find a quantitative relationship between monitored cell parameters and the emissions of CF4. To achieve this goal, a predictive algorithm has been developed using seven cell indicators. These indicators are based on the cell voltage, the noise level and other parameters calculated from individual anode current monitoring. The predictive algorithm is structured into three different
steps. The first two steps give qualitative information while the third one quantitatively describes the expected CF4 concentration at the duct end of the electrolysis cells. Validations after each step are presented and discussed. Finally, a sensitivity analysis was performed to understand the effect of each indicator on the onset of low-voltage PFC emissions. The standard deviation of
individual anode currents was found to be the dominant variable. Cell voltage, noise level, and maximum individual anode current also showed a significant
correlation with the presence of CF4 in the output gas of an electrolysis cell
Gaseous Dark Matter Detectors
Dark Matter detectors with directional sensitivity have the potential of
yielding an unambiguous positive observation of WIMPs as well as discriminating
between galactic Dark Matter halo models. In this article, we introduce the
motivation for directional detectors, discuss the experimental techniques that
make directional detection possible, and review the status of the experimental
effort in this field.Comment: 19 pages, review on gaseous directional dark matter detectors
submitted to New Journal of Physic
Skyrmions from a Born-Infeld Action
We consider a geometrically motivated Skyrme model based on a general
covariant kinetic term proposed originally by Born and Infeld. We introduce
this new term by generalizing the Born-Infeld action to a non-abelian
gauge theory and by using the hidden gauge symmetry formalism. The static
properties of the Skyrmion are then analyzed and compared with other
Skyrme-like models.Comment: 11 pages, 4 figures (not included), revtex v3, LAVAL-PHY-11-9
Counterterrorism in the Philippines: Review of Key Issues
Terrorism has taken root in almost all corners of the world with terrorist organizations thriving in both rich and poor countries. In the Philippines, the Human Security Act of 2007 came into force to address the threat of terrorism to the national security of the country. However, the law has never been fully utilized. To provide law enforcers with a stronger legal measure to address acts of terrorism in the country, President Duterte certified a new Anti-Terrorism Bill as urgent, with Congress adopting the Senate version and approving it in the shortest time possible. Despite opposition from various sectors and growing concerns over some of its provisions, President Duterte signed this into law, officially becoming Republic Act No. 11479 or the Anti-Terrorism Act of 2020. This article briefly reviews some key issues of counterterrorism measures in the Philippines
Leptoquark pair production at the Fermilab Tevatron: Signal and backgrounds
We perform a Monte-Carlo simulation of scalar leptoquark pair production at
the Tevatron (energy =1.8 TeV and luminosity =100 pb^{-1}) with ISAJET. We also
investigate the dominant sources of Standard Model background: Z*jj, ZZ
production and heavy quark top-antitop. We find that the top-antitop background
is the most important except near the Z pole where the Z*jj background is
peaked. We also evaluate the signal-to-background ratio and find a discovery
reach of 130 GeV (170 GeV) for a branching ratio of B(LQ-> eq)=0.5 (B=1).Comment: 8 pages, 6 figures, latex (revtex
Caregiver responses to symptoms of first-onset psychosis: A comparative study of Chinese-and Euro-Canadian families
Considerable evidence suggests that ethnic Chinese families in Canada are reluctant to seek psychiatric treatment for a relative with mental illness. The following hypotheses were investigated: (a) longer delay in seeking treatment among Chinese versus Euro-Canadians; (b) greater burden among Chinese versus Euro-Canadians; and (c) more negative conceptions of mental illness among Chinese versus Euro-Canadians. The sample consisted of 18 Chinese Canadians and 36 Euro-Canadians experiencing a first episode of psychosis; each participant recruited a parent or sibling who responded to measures of perceived family burden and attitudes toward mental illness. Results confirmed all three hypotheses. Chinese care-givers were particularly more likely to endorse the practice of keeping mental illness a secret from others, as well as withdrawal from individuals with mental illness. These findings suggest that Chinese caregivers were more affected by the stigma of mental illness than were Euro-Canadian caregivers
Field-angle dependence of sound velocity in the Weyl semimetal TaAs
The elastic modulus of a single crystal of the Weyl semimetal TaAs
was investigated by measuring relative changes in the sound velocity under
application of a magnetic field up to 10 T. Using an ultrasonic pulsed-echo
technique, we studied the shear response of the crystal when the angle between
the sound wave propagation and the magnetic field is changed. We observe a
broken tetragonal symmetry at fields above 6 T, an anisotropy that is likely
related to a longitudinal negative magnetoresistance and therefore might
provide evidence of the chiral anomaly, one of the main topological signatures
of this class of materials. We also observe quantum oscillations in the sound
velocity whose frequencies vary with magnetic field orientation. A fan diagram
of Landau level indices reveals topological and trivial Berry phases, depending
on the field orientation, indicating a sensitivity to different Fermi surface
pockets that do or do not enclose Weyl nodes respectively
The propensity of molecules to spatially align in intense light fields
The propensity of molecules to spatially align along the polarization vector
of intense, pulsed light fields is related to readily-accessible parameters
(molecular polarizabilities, moment of inertia, peak intensity of the light and
its pulse duration). Predictions can now be made of which molecules can be
spatially aligned, and under what circumstances, upon irradiation by intense
light. Accounting for both enhanced ionization and hyperpolarizability, it is
shown that {\it all} molecules can be aligned, even those with the smallest
static polarizability, when subjected to the shortest available laser pulses
(of sufficient intensity).Comment: 8 pages, 4 figures, to be submitted to PR
Vulnerability analysis of satellite-based synchronized smart grids monitoring systems
The large-scale deployment of wide-area monitoring systems could play a strategic role in supporting the evolution of traditional power systems toward smarter and self-healing grids. The correct operation of these synchronized monitoring systems requires a common and accurate timing reference usually provided by a satellite-based global positioning system. Although these satellites signals provide timing accuracy that easily exceeds the needs of the power industry, they are extremely vulnerable to radio frequency interference. Consequently, a comprehensive analysis aimed at identifying their potential vulnerabilities is of paramount importance for correct and safe wide-area monitoring system operation. Armed with such a vision, this article presents and discusses the results of an experimental analysis aimed at characterizing the vulnerability of global positioning system based wide-area monitoring systems to external interferences. The article outlines the potential strategies that could be adopted to protect global positioning system receivers from external cyber-attacks and proposes decentralized defense strategies based on self-organizing sensor networks aimed at assuring correct time synchronization in the presence of external attacks
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