1,276 research outputs found
Wideband digital phase comparator for high current shunts
A wideband phase comparator for precise measurements of phase difference of
high current shunts has been developed at INRIM. The two-input digital phase
detector is realized with a precision wideband digitizer connected through a
pair of symmetric active guarded transformers to the outputs of the shunts
under comparison. Data are first acquired asynchronously, and then transferred
from on-board memory to host memory. Because of the large amount of data
collected the filtering process and the analysis algorithms are performed
outside the acquisition routine. Most of the systematic errors can be
compensated by a proper inversion procedure.
The system is suitable for comparing shunts in a wide range of currents, from
several hundred of milliampere up to 100 A, and frequencies ranging between 500
Hz and 100 kHz. Expanded uncertainty (k=2) less than 0.05 mrad, for frequency
up to 100 kHz, is obtained in the measurement of the phase difference of a
group of 10 A shunts, provided by some European NMIs, using a digitizer with
sampling frequency up to 1 MHz. An enhanced version of the phase comparator
employs a new digital phase detector with higher sampling frequency and
vertical resolution. This permits to decrease the contribution to the
uncertainty budget of the phase detector of a factor two from 20 kHz to 100
kHz. Theories and experiments show that the phase difference between two high
precision wideband digitizers, coupled as phase detector, depends on multiple
factors derived from both analog and digital imprint of each sampling system.Comment: 20 pages, 9 figure
Investigating on the nuclear obscuration in two types of Seyfert 2 galaxies
We build a large sample of Seyfert 2 galaxies (Sy2s) with both optical
spectropolarimetric and X-ray data available, in which 29 Sy2s with the
detection of polarized broad emission line (PBL) and 25 without. We find that
for luminous Sy2s with L_[OIII] > 10^41 erg/s, sources with PBL have smaller
X-ray absorption column density comparing with those without PBL (at 92.3%
confidence level): most of the Sy2s with N_H<10^23.8 cm^-2 show PBL (86%, 12
out 14), while the fraction is much smaller for sources with heavier
obscuration (54%, 15 out 28). The confidence level of the difference in
absorption bounces up to 99.1% while using the "T" ratio (F_2-10keV/F_[O III])
as an indicator. We rule out observation or selection bias as the origin for
the difference. Our results, for the first time with high statistical
confidence, show that, in additional to the nuclei activity, the nuclear
obscuration also plays an important role in the visibility of PBL in Sy2s.
These results can be interpreted in the framework of the unified model. We can
reach these results in the unified model if: a) the absorption column density
is higher at large inclinations and b) the scattering region is obscured at
large inclinations.Comment: 28 pages, including 7 figures and 3 tables, ApJ accepte
The development of policing in Britain in the next five years.
The British police service is currently going through a radical transformation phase. The present Tory-led
coalition government has set out an agenda to bring about drastic changes in policing. These proposed
changes are unprecedented in the history of policing since 1829.
The police service is governed by a tripartite arrangement of checks and balances laid down under the
Police Act 1964. By this I mean that there are three key players in relation to police governance in Britain: the
Home Secretary, the local police authority and the chief constable. The future of policing in the next five
years is set out clearly by the Home Secretary, Theresa May MP, under the Police Reform and Social
Responsibility Bill, which is currently being reviewed in the House of Lords.
The recent phone hacking scandal has made it imperative for the British public to have a closer look at the
police service in relation to proper accountability. There have been references to police corruption as far
back as the era of 'parish constables', dating back to 1800, when it was alleged that police officers took
bribes, got drunk whilst on duty and lacked moral credibility to protect and serve us (Critchley, 1978). In the
seventies and eighties the British public was informed of another scandal involving members of Scotland
Yard and criminal gangs in the East End of London. In this article, I shall argue that the issue of police
corruption is not a new phenomenon. It is has been an ongoing issue that has haunted the police for over a
century.
This article is divided into three parts. In the first part of the article I present the following issues: the
Metropolitan Police policing plan 2011-2014; the merits and demerits of the policing plan; tripartite police
accountability and its shortcomings; democratic accountability and localisation of policing; the
professionalisation of policing and the creation of the Police Body; review of police pay and benefits; and the
impact of this on police officers' morale.
In the second part of my article I present some of the criticisms levelled against the ongoing police reforms. I
will look at the criticisms from both internal and external perspectives. By internal criticism, I mean police
officers' opposition to the reforms. By external criticism, I mean criticisms from criminologists and members
of the British public.
In the third part of my article I made my position clear on where I stand in relation to the ongoing police
reforms. I shall argue that the current ongoing job cuts in the police service are a disaster waiting to happen,
and that our safety has been compromised by politicians. We are now living at the mercy of criminals and law breakers due to manpower shortage. We are all living witnesses to the ongoing public disturbances in
Tottenham, Enfield, Brixton, Peckham, Walthamstow and Croydon, in London. The speed of the spread of
these riots to other cities like Bristol, Birmingham, Manchester and Liverpool occurred on an unimaginable
scale. We all watched how difficult it was for the police to restore order and normality. Rioters looted and
plundered goods and burnt down buildings as if no laws existed in our country. A complete breakdown of law
and order put the lives of citizens at risk.
My article makes a passionate appeal to the present coalition government to rethink the issue of reducing the
numbers of police officers protecting us. I shall argue that we need more police officers in Britain not fewer.
The level of anger and social discontent is higher than the government ever anticipated, partly because of
economic hardship. My argument is that economic hardship is not an excuse to commit burglary, theft,
arson, murder and criminal damage with intent to endanger life. Rioters are shameless opportunists, a bunch
of hoodlums, criminals who have no place in any civilised society, who should be made to face the due
process of law
Time-odd mean fields in the rotating frame: microscopic nature of nuclear magnetism
The microscopic role of nuclear magnetism in rotating frame is investigated
for the first time in the framework of the cranked relativistic mean field
theory. It is shown that nuclear magnetism modifies the expectation values of
single-particle spin, orbital and total angular momenta along the rotational
axis effectively creating additional angular momentum. This effect leads to the
increase of kinematic and dynamic moments of inertia at given rotational
frequency and has an impact on effective alignments.Comment: 16 pages, 4 figures, submitted to Physical Review
Riemann's theorem for quantum tilted rotors
The angular momentum, angular velocity, Kelvin circulation, and vortex
velocity vectors of a quantum Riemann rotor are proven to be either (1) aligned
with a principal axis or (2) lie in a principal plane of the inertia ellipsoid.
In the second case, the ratios of the components of the Kelvin circulation to
the corresponding components of the angular momentum, and the ratios of the
components of the angular velocity to those of the vortex velocity are analytic
functions of the axes lengths.Comment: 8 pages, Phys. Rev.
A Radio Study of the Seyfert Galaxy IC 5063: Evidence for Fast Gas Outflow
New radio continuum (8 GHz and 1.4 GHz) and HI 21 cm line observations of the
Seyfert 2 galaxy IC 5063 (PKS 2048-572) were obtained with the Australia
Telescope Compact Array (ATCA). The 8 GHz image reveals a linear triple
structure (~4'', 1.5 kpc) oriented perpendicular to the optical polarization
position angle. It is aligned with the inner dust lane and shows strong
morphological association with the narrow emission line region (NLR). At 21 cm,
very broad (~700 km/s) HI absorption is observed against the strong continuum
source. This absorption is almost entirely blueshifted, indicating a fast net
outflow, but a faint and narrow redshifted component is also present. In IC
5063 we see clear evidence for strong shocks resulting from the radio
plasma-ISM interaction in the central few kpc. However, the energy flux in the
radio plasma is an order of magnitude smaller than the energy emitted in
emission lines. Thus, shocks are unlikely to account solely for the global
ionization of the emission line region, particularly at large distances.
The HI emission outlines a warped disk associated with the system of dust
lanes some ~2' (~38 kpc) in radius. The lack of kinematically disturbed gas
outside the central few kpc, coupled with the disk warp and close morphological
connection of the inner dust lanes and the large-scale ionized gas, support the
idea that the gas at large radii is photoionized by the central region, while
shadowing effects are important in defining its X-shaped morphology. The
kinematics of the ionized and of the neutral gas suggests the existence of a
dark halo.Comment: 18 pages, 8 Postscript figures, 3 jpeg figures, Postscript preprint
is available from http://jhufos.pha.jhu.edu/~zlatan/papers.htm
Self-consistent anisotropic oscillator with cranked angular and vortex velocities
The Kelvin circulation is the kinematical Hermitian observable that measures
the true character of nuclear rotation. For the anisotropic oscillator, mean
field solutions with fixed angular momentum and Kelvin circulation are derived
in analytic form. The cranking Lagrange multipliers corresponding to the two
constraints are the angular and vortex velocities. Self-consistent solutions
are reported with a constraint to constant volume.Comment: 12 pages, LaTex/RevTex, Phys. Rev. C4
The Unified Model & Evolution of Active Galaxies: Implications from a Spectropolarimetric Study
We extend the analysis presented in Tran (2001) of a spectropolarimetric
survey of the CfA and 12micron samples of Seyfert 2 galaxies (S2s). We confirm
that S2s with hidden broad line regions (HBLRs) tend to have hotter
circumnuclear dust temperatures, show mid-IR spectra more characteristic of S1
galaxies, and are intrinsically more luminous than non-HBLR S2s. The level of
obscuration and circumnuclear star formation, however, appear to be similar
between HBLR and non-HBLR S2 galaxies, based on an examination of various
observational indicators. HBLR S2s, on average, share many similar large-scale,
presumably isotropic, characteristics with Seyfert 1 galaxies (S1s), as would
be expected if the unified model is correct, while non-HBLR S2s generally do
not. The active nuclear engines of non-HBLR S2s then, appear to be truly weaker
than HBLR S2s, which in turn, are fully consistent with being S1s viewed from
another direction. There is also evidence that the fraction of detected HBLR
increases with radio power of the AGN. Thus, not all Seyfert 2 galaxies may be
intrinsically similar in nature, and we speculate that evolutionary processes
may be at work.Comment: 15 pages with embedded figs, ApJ in press, vol. 583, 2003 Feb. 1. v2:
minor corrections to text, some typos removed; updated reference list: some
added, some remove
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