7,992 research outputs found
Twist-3 contributions to processes in perturbative QCD approach
As one of the simplest hadronic processes, () could be a good testing ground for our understanding of
the perturbative and nonperturbative structure of QCD, and will be studied with
high precision at BELLE-\RNum{2} in the near future. In this paper, we revisit
these processes with twist-3 corrections in the perturbative QCD approach based
on the factorization theorem, in which transverse degrees of freedom as
well as resummation effects are taken into account. The influence of the
distribution amplitudes on the cross sections are discussed in detail. Our work
shows that not only the transverse momentum effects but also the twist-3
corrections play a significant role in the processes in the intermediate energy region. Especially in the few GeV
region, the twist-3 contributions become dominant in the cross sections. And it
is noteworthy that both the twist-3 result of the cross
section and that of the cross section agree well with the BELLE
and ALEPH measurements. For the pion and kaon angular distributions, there
still exist discrepancies between our results and the experimental
measurements. Possible reasons for these discrepancies are discussed briefly.Comment: 19 pages, 7 figures and 2 tables. Contents improved and more
discussions adde
Set Representations of Linegraphs
Let be a graph with vertex set and edge set . A family
of nonempty sets is a set representation of
if there exists a one-to-one correspondence between the vertices in and the sets in such that if and only if S_i\cap S_j\neq \es. A set representation
is a distinct (respectively, antichain, uniform and simple) set representation
if any two sets and in have the property (respectively, , and ). Let . Two set
representations and are isomorphic if
can be obtained from by a bijection from
to . Let denote a class of set
representations of a graph . The type of is the number of equivalence
classes under the isomorphism relation. In this paper, we investigate types of
set representations for linegraphs. We determine the types for the following
categories of set representations: simple-distinct, simple-antichain,
simple-uniform and simple-distinct-uniform
Data Detection and Code Channel Allocation for Frequency-Domain Spread ACO-OFDM Systems Over Indoor Diffuse Wireless Channels
Future optical wireless communication systems promise to provide high-speed data transmission in indoor diffuse environments. This paper considers frequency-domain spread asymmetrically clipped optical orthogonal frequency-division multiplexing (ACOOFDM) systems in indoor diffuse channels and aims to develop efficient data detection and code channel allocation schemes. By exploiting the frequency-domain spread concept, a linear multi-code detection scheme is proposed to maximize the signal to interference plus noise ratio (SINR) at the receiver. The achieved SINR and bit error ratio (BER) performance are analyzed. A computationally efficient code channel allocation algorithm is proposed to improve the BER performance of the frequency-domain spread ACO-OFDM system.
Numerical results show that the frequency-domain spread ACO-OFDM system outperforms conventional ACO-OFDM systems in indoor diffuse channels. Moreover, the proposed linear multi-code detection and code channel allocation algorithm can improve the performance of optical peak-to-average power ratio (PAPR
Periodic Radio Variability in NRAO 530: Phase Dispersion Minimization Analysis
In this paper, a periodicity analysis of the radio light curves of the blazar
NRAO 530 at 14.5, 8.0, and 4.8 GHz is presented employing an improved Phase
Dispersion Minimization (PDM) technique. The result, which shows two persistent
periodic components of and years at all three frequencies,
is consistent with the results obtained with the Lomb-Scargle periodogram and
weighted wavelet Z-transform algorithms. The reliability of the derived
periodicities is confirmed by the Monte Carlo numerical simulations which show
a high statistical confidence. (Quasi-)Periodic fluctuations of the radio
luminosity of NRAO 530 might be associated with the oscillations of the
accretion disk triggered by hydrodynamic instabilities of the accreted flow.
\keywords{methods: statistical -- galaxies: active -- galaxies: quasar:
individual: NRAO 530}Comment: 8 pages, 5 figures, accepted by RA
Application of Neural-Like P Systems With State Values for Power Coordination of Photovoltaic/Battery Microgrids
The power coordination control of a photovoltaic/battery microgrid is performed with a novel
bio-computing model within the framework of membrane computing. First, a neural-like P system with
state values (SVNPS) is proposed for describing complex logical relationships between different modes
of Photovoltaic (PV) units and energy storage units. After comparing the objects in the neurons with the
thresholds, state values will be obtained to determine the con guration of the SVNPS. Considering the
characteristics of PV/battery microgrids, an operation control strategy based on bus voltages of the point of
common coupling and charging/discharging statuses of batteries is proposed. At rst, the SVNPS is used to
construct the complicated unit working modes; each unit of the microgrid can adjust the operation modes
automatically. After that, the output power of each unit is reasonably coordinated to ensure the operation
stability of the microgrid. Finally, a PV/battery microgrid, including two PV units, one storage unit, and
some loads are taken into consideration, and experimental results show the feasibility and effectiveness of
the proposed control strategy and the SVNPS-based power coordination control models
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