7,132 research outputs found
Further investigation of a contactless patient-electrode interface of an Electrical Impedance Mammography system
The Sussex Mk4 Electrical Impedance Mammography (EIM) system is a novel instrument, designed for the detection of early breast cancer, based upon Electrical Impedance Tomography (EIT). Many innovations in the field have been incorporated in the design improving both signal distribution and response. This paper investigates the behaviour of the contactless patient-electrode interface. The interface was studied in detail using phantom and healthy volunteer, in-vivo, data. Our findings show the necessity for the careful design of electrode enclosure so that the response of the system is not affected by the unpredictable positioning of the breast; it closely mimics those conditions seen when using the phantom. The paper includes a number of possible designs and their individual characteristics. In addition an explanation on the unanticipated effects and solutions for such are described. © 2010 IOP Publishing Ltd
PSR 0943+10: a bare strange star?
Recent work by Rankin & Deshpande strongly suggests that there exist strong
``micro-storms'' rotating around the magnetic axis of the 1.1s pulsar PSR
0943+10. Such a feature hints that most probably the large-voltage vacuum gap
proposed by Ruderman & Sutherland (RS) does exist in the pulsar polar cap.
However, there are severe arguments against the formation of the RS-type gap in
pulsars, since the binding energies of both the Fe ions and the electrons in a
neutron star's surface layer is too small to prevent thermionic ejection of the
particles from the surface. Here we propose that PSR 0943+10 (probably also
most of the other ``drifting'' pulsars) might be bare strange stars rather than
normal neutron stars, in which the ``binding energy'' at the surface is merely
infinity either for the case of ``pulsar'' or ``anti-pulsar''. It is further
proposed that identifying a drifting pulsar as an anti-pulsar is the key
criterion to distinguish strange stars from neutron stars.Comment: 4 pages, no figures, LaTeX, accepted 1999 July 9 by ApJ Letter
Cryptanalysis of an MPEG-Video Encryption Scheme Based on Secret Huffman Tables
This paper studies the security of a recently-proposed MPEG-video encryption
scheme based on secret Huffman tables. Our cryptanalysis shows that: 1) the key
space of the encryption scheme is not sufficiently large against
divide-and-conquer (DAC) attack and known-plaintext attack; 2) it is possible
to decrypt a cipher-video with a partially-known key, thus dramatically
reducing the complexity of the DAC brute-force attack in some cases; 3) its
security against the chosen-plaintext attack is very weak. Some experimental
results are included to support the cryptanalytic results with a brief discuss
on how to improve this MPEG-video encryption scheme.Comment: 8 pages, 4 figure
A variant transfer matrix method suitable for transport through multi-probe systems
We have developed a variant transfer matrix method that is suitable for
transport through multi-probe systems. Using this method, we have numerically
studied the quantum spin Hall effect (QSHE) on 2D graphene with both intrinsic
(Vso) and Rashba (Vr) spin-orbit (SO) couplings. The integer QSHE arises in the
presence of intrinsic SO interaction and is gradually destroyed by the Rashba
SO interaction and disorder fluctuation. We have numerically determined the
phase boundaries separating integer QSHE and spin Hall liquid. We have found
that when Vso> 0.2t with t the hopping constant the energy gap needed for the
integer QSHE is the largest satisfying |E|<t. For smaller Vso the energy gap
decreases linearly. In the presence of Rashba SO interaction or disorders, the
energy gap diminishes. With Rashba SO interaction the integer QSHE is robust at
the largest energy within the energy gap while at the smallest energy within
the energy gap the integer QSHE is insensitive to the disorder
The Current Flows in Pulsar Magnetospheres
The global structure of the current flows in pulsar magnetospheres is
investigated, with rough calculations of the elements in the magnetospheric
circuit. It is emphasized that the potential of critical field lines is the
same as that of interstellar medium, and that the pulsars whose rotation axes
and magnetic dipole axes are parallel should be positively charged, in order to
close the pulsar's current flows. The statistical relation between the radio
luminosity and pulsar's electric charge (or the spindown power) may hint that
the millisecond pulsars could be low-mass bare strange stars.Comment: 10 pages, 4 figure
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