41,201 research outputs found
Factorization of Radiative Leptonic Decays of and Mesons Including the Soft Photon Region
In this work, we study the radiative leptonic decays of and
mesons using factorization approach. Factorization is proved to be valid
explicitly at 1-loop level at any order of . We consider the contribution in the soft photon region
that . The numerical
results shows that, the soft photon region is very important for both the
and mesons. The branching ratios of is , which is about times of the result obtained by only considering
the hard photon region . And for the case of , the result of the branching ratio is .Comment: arXiv admin note: text overlap with arXiv:1409.035
Factorization of Radiative Leptonic Decays of and Mesons
In this work, we study the factorization of the radiative leptonic decays of
and mesons, the contributions of the order are taken into account. The factorization is proved to
be valid explicitly at the order . The hard kernel is obtained. The numerical results are
calculated using the wave-function obtained in relativistic potential model.
The contribution is found to be very
important, the correction to the decay amplitudes of
is about . For mesons, the contributions are more important.Comment: 26 pages, 8 figures. Version to appear in Nucl. Phys.
Parametric pitch instability investigation of Deep Draft Semi-submersible platform in irregular waves
Parametric pitch instability of a Deep Draft Semi-submersible platform (DDS) is investigated in irregular waves. Parametric pitch is a form of parametric instability, which occurs when parameters of a system vary with time and the variation satisfies a certain condition. In previous studies, analyzing of parametric instability is mainly limited to regular waves, whereas the realistic sea conditions are irregular waves. Besides, parametric instability also occurs in irregular waves in some experiments. This study predicts parametric pitch of a Deep Draft Semi-submersible platform in irregular waves. Heave motion of DDS is simulated by wave spectrum and response amplitude operator (RAO). Then Hill equation for DDS pitch motion in irregular waves is derived based on linear-wave theory. By using Bubnov-Galerkin approach to solve Hill equation, the corresponding stability chart is obtained. The differences between regular-waves stability chart and irregular-waves stability chart are compared. Then the sensitivity of wave parameters on DDS parametric pitch in irregular waves is discussed. Based on the discussion, some suggestions for the DDS design are proposed to avoid parametric pitch by choosing appropriate parameters. The results indicate that it's important and necessary to predict DDS parametric pitch in irregular waves during design process
The Hitting Times of A Stochastic Epidemic Model
In this paper, we focus on the hitting times of a stochastic epidemic model
presented by \cite{Gray}. Under the help of the auxiliary stopping times, we
investigate the asymptotic limits of the hitting times by the variations of
calculus and the large deviation inequalities when the noise is sufficiently
small. It can be shown that the relative position between the initial state and
the hitting state determines the scope of the hitting times greatly
Towards a Simple Relationship to Estimate the Capacity of Static and Mobile Wireless Networks
Extensive research has been done on studying the capacity of wireless
multi-hop networks. These efforts have led to many sophisticated and customized
analytical studies on the capacity of particular networks. While most of the
analyses are intellectually challenging, they lack universal properties that
can be extended to study the capacity of a different network. In this paper, we
sift through various capacity-impacting parameters and present a simple
relationship that can be used to estimate the capacity of both static and
mobile networks. Specifically, we show that the network capacity is determined
by the average number of simultaneous transmissions, the link capacity and the
average number of transmissions required to deliver a packet to its
destination. Our result is valid for both finite networks and asymptotically
infinite networks. We then use this result to explain and better understand the
insights of some existing results on the capacity of static networks, mobile
networks and hybrid networks and the multicast capacity. The capacity analysis
using the aforementioned relationship often becomes simpler. The relationship
can be used as a powerful tool to estimate the capacity of different networks.
Our work makes important contributions towards developing a generic methodology
for network capacity analysis that is applicable to a variety of different
scenarios.Comment: accepted to appear in IEEE Transactions on Wireless Communication
Comparison theorem of one-dimensional stochastic hybrid delay systems
The comparison theorem of stochastic differential equations has been investigated by many authors. However, little research is available on the comparison theorem of stochastic hybrid systems, which is the topic of this paper. The systems discussed is stochastic delay differential equations with Markovian switching. It is an important class of hybrid systems
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