23,019 research outputs found
Multiple charge beam dynamics in Alternate Phase Focusing structure
Asymmetrical Alternate Phase (A-APF) focusing realized in a sequence of 36
Superconducting Quarter Wave Resonators has been shown to accelerate almost 81
% of input Uranium beam before foil stripper to an energy of 6.2 MeV/u from 1.3
MeV/u. Ten charge states from 34+ to 43+ could be simultaneously accelerated
with the phase of resonators tuned for 34+. A-APF structure showed unique
nature of large potential bucket for charge states higher than that of tuned
one. Steering inherent to QWRs can be mitigated by selecting appropriate phase
variation of the APF periods and optimization of solenoid field strengths
placed in each of the periods. This mitigation facilitates multiple charge
state acceleration schemeComment: 10 pages, 8 figure
Intact sublimation of silicon nanocrystals evidenced via HREM imaging and EELS in a dedicated STEM
Bosonic Super Liouville System: Lax Pair and Solution
We study the bosonic super Liouville system which is a statistical
transmutation of super Liouville system. Lax pair for the bosonic super
Liouville system is constructed using prolongation method, ensuring the Lax
integrability, and the solution to the equations of motion is also considered
via Leznov-Saveliev analysis.Comment: LaTeX, no figures, 11 page
Two-Way Training for Discriminatory Channel Estimation in Wireless MIMO Systems
This work examines the use of two-way training to efficiently discriminate
the channel estimation performances at a legitimate receiver (LR) and an
unauthorized receiver (UR) in a multiple-input multiple-output (MIMO) wireless
system. This work improves upon the original discriminatory channel estimation
(DCE) scheme proposed by Chang et al where multiple stages of feedback and
retraining were used. While most studies on physical layer secrecy are under
the information-theoretic framework and focus directly on the data transmission
phase, studies on DCE focus on the training phase and aim to provide a
practical signal processing technique to discriminate between the channel
estimation performances at LR and UR. A key feature of DCE designs is the
insertion of artificial noise (AN) in the training signal to degrade the
channel estimation performance at UR. To do so, AN must be placed in a
carefully chosen subspace based on the transmitter's knowledge of LR's channel
in order to minimize its effect on LR. In this paper, we adopt the idea of
two-way training that allows both the transmitter and LR to send training
signals to facilitate channel estimation at both ends. Both reciprocal and
non-reciprocal channels are considered and a two-way DCE scheme is proposed for
each scenario. {For mathematical tractability, we assume that all terminals
employ the linear minimum mean square error criterion for channel estimation.
Based on the mean square error (MSE) of the channel estimates at all
terminals,} we formulate and solve an optimization problem where the optimal
power allocation between the training signal and AN is found by minimizing the
MSE of LR's channel estimate subject to a constraint on the MSE achievable at
UR. Numerical results show that the proposed DCE schemes can effectively
discriminate between the channel estimation and hence the data detection
performances at LR and UR.Comment: 1
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