2,309 research outputs found
Multidimensional Trellis Coded Phase Modulation Using a Multilevel Concatenation Approach
The first part of this paper presents a simple and systematic technique for constructing multidimensional M-ary phase shift keying (MMK) trellis coded modulation (TCM) codes. The construction is based on a multilevel concatenation approach in which binary convolutional codes with good free branch distances are used as the outer codes and block MPSK modulation codes are used as the inner codes (or the signal spaces). Conditions on phase invariance of these codes are derived and a multistage decoding scheme for these codes is proposed. The proposed technique can be used to construct good codes for both the additive white Gaussian noise (AWGN) and fading channels as is shown in the second part of this paper
Photoluminescence pressure coefficients of InAs/GaAs quantum dots
We have investigated the band-gap pressure coefficients of self-assembled
InAs/GaAs quantum dots by calculating 17 systems with different quantum dot
shape, size, and alloying profile using atomistic empirical pseudopotential
method within the ``strained linear combination of bulk bands'' approach. Our
results confirm the experimentally observed significant reductions of the band
gap pressure coefficients from the bulk values. We show that the nonlinear
pressure coefficients of the bulk InAs and GaAs are responsible for these
reductions. We also find a rough universal pressure coefficient versus band gap
relationship which agrees quantitatively with the experimental results. We find
linear relationships between the percentage of electron wavefunction on the
GaAs and the quantum dot band gaps and pressure coefficients. These linear
relationships can be used to get the information of the electron wavefunctions.Comment: 8 pages, 2 tables, 4 figure
Possible molecular states from interactions of charmed baryons
In this work, we perform a systematic study of possible molecular states
composed of two charmed baryons including hidden-charm systems
, , and
, and corresponding double-charm systems
, , and
. With the help of the heavy quark chiral effective
Lagrangians, the interactions are described with , , ,
, , and exchanges. The potential kernels are
constructed, and inserted into the quasipotential Bethe-Salpeter equation. The
bound states from the interactions considered is studied by searching for the
poles of the scattering amplitude. The results suggest that strong attractions
exist in both hidden-charm and double-charm systems considered in the current
work, and bound states can be produced in most of the systems. More experiment
studies about these molecular states are suggested though the nucleon-nucleon
collison at LHC and nucleon-antinucleon collison at .Comment: 7 pages, 5 figure
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