2,710 research outputs found
Summary Report of the Spin Physics Working Group
The contributions to the Spin Physics WG are summarized. Several new
experimental results and plans for new measurements have been reported. An
improved theoretical understanding of the most recent hot topics in spin
physics has been discussed by many authors especially in the new fields of the
transversity and generalized parton distributions.Comment: 20 pages, 14 Postscript figures, summary talk presented at the 9th
International Workshop on Deep Inelastic Scattering (DIS 2001), Bologna,
April 200
A Physical Layer Secured Key Distribution Technique for IEEE 802.11g Wireless Networks
Key distribution and renewing in wireless local area networks is a crucial
issue to guarantee that unauthorized users are prevented from accessing the
network. In this paper, we propose a technique for allowing an automatic
bootstrap and periodic renewing of the network key by exploiting physical layer
security principles, that is, the inherent differences among transmission
channels. The proposed technique is based on scrambling of groups of
consecutive packets and does not need the use of an initial authentication nor
automatic repeat request protocols. We present a modification of the scrambling
circuits included in the IEEE 802.11g standard which allows for a suitable
error propagation at the unauthorized receiver, thus achieving physical layer
security.Comment: 9 pages, 7 figures. Accepted for publication in IEEE Wireless
Communications Letters. Copyright transferred to IEE
Improving the efficiency of the LDPC code-based McEliece cryptosystem through irregular codes
We consider the framework of the McEliece cryptosystem based on LDPC codes,
which is a promising post-quantum alternative to classical public key
cryptosystems. The use of LDPC codes in this context allows to achieve good
security levels with very compact keys, which is an important advantage over
the classical McEliece cryptosystem based on Goppa codes. However, only regular
LDPC codes have been considered up to now, while some further improvement can
be achieved by using irregular LDPC codes, which are known to achieve better
error correction performance than regular LDPC codes. This is shown in this
paper, for the first time at our knowledge. The possible use of irregular
transformation matrices is also investigated, which further increases the
efficiency of the system, especially in regard to the public key size.Comment: 6 pages, 3 figures, presented at ISCC 201
Low-power Secret-key Agreement over OFDM
Information-theoretic secret-key agreement is perhaps the most practically
feasible mechanism that provides unconditional security at the physical layer
to date. In this paper, we consider the problem of secret-key agreement by
sharing randomness at low power over an orthogonal frequency division
multiplexing (OFDM) link, in the presence of an eavesdropper. The low power
assumption greatly simplifies the design of the randomness sharing scheme, even
in a fading channel scenario. We assess the performance of the proposed system
in terms of secrecy key rate and show that a practical approach to key sharing
is obtained by using low-density parity check (LDPC) codes for information
reconciliation. Numerical results confirm the merits of the proposed approach
as a feasible and practical solution. Moreover, the outage formulation allows
to implement secret-key agreement even when only statistical knowledge of the
eavesdropper channel is available.Comment: 9 pages, 4 figures; this is the authors prepared version of the paper
with the same name accepted for HotWiSec 2013, the Second ACM Workshop on Hot
Topics on Wireless Network Security and Privacy, Budapest, Hungary 17-19
April 201
Selection criteria and robust optimization of a traction PM-Assisted Synchronous Reluctance motor
In the coming years, the electrification and the deployment of the electric motors in the urban transports will become a more and more widespread reality. The optimization stage of the electric motors usually does not consider in detail the real driving conditions of the car in which the motor is installed. It follows that the actual motor performance in operating points, particularly as regards the torque ripple and the efficiency, might be worse than expected. A robust solution is a required target. This paper deals with the design and optimization of a high-speed permanent-magnet-assisted synchronous reluctance motor for traction applications, taking into account both city and highway driving cycles. A procedure is employed in order to evaluate the most representative operating points, which have to be considered when a global optimization is required. An analysis of the solution robustness has been performed. Both results and advantages of the adopted methodology are highlighted
Design criteria for grinding machine dynamic stability
Abstract Surface grinding is one of the oldest and most widely used machining process: to date, there are still few alternatives available for producing smooth and flat surfaces, satisfying both technical and economic constraints. The quality of a workpiece resulting from a grinding process is strongly influenced by the static and dynamic behavior of the mechanical system, composed by machine tool, wheel, fixture and workpiece. In particular, the dynamic compliance of the machine at wheel-workpiece interface may cause vibrations leading to poor surface quality. Starting from the analysis of process-machine interaction according to self-excited vibrations theories (the most relevant), this paper outlines a path for surface grinding machines design, focused on the identification of the most critical dynamic eigenmodes both in terms of dynamical parameters and geometry (vibration direction). The methodology is based on the application of Nyquist stability criterion for MIMO systems. Firstly, the methodology distinguishes between a limitation mainly ascribable to regenerative chatter and one ascribable to closed-loop eigenmodes properties. In this latter case, it will be shown that stability properties are strongly influenced by the shape and orientation of the elliptical movement of the wheel entailed by the limiting eigenmode (that, in general, is complex). Such an analysis can be also exploited to provide some indications guiding machine structural modifications. Finally, the approach is demonstrated on a couple of grinding machine variants via FE modeling
Electroproduction of hadrons in nuclei
Recent results from HERMES and expectations from Jlab in the hadron leptoproduction of nuclei are presented. The possible interpretations in terms of medium modifications of the parton fragmentation function and the implications on the parton energy loss are discussed
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