Persistence of Semi-Trajectories

We consider diffeomorphisms f of a smooth compact riemannian mainfold M and its suspension flow . Assuming some regularity of the stable (unstable) sets at the points we prove the persistence in the future of {f ⁿ (x), n ≥ 0} or , i.e., that C ⁰ small perturbations g of f have a semi-trajectory that closely shadows {f ⁿ (x), n ≥ 0} and that the suspension of g has also a semi-trajectory that closely shadows . In case x belongs to a minimal set of f we show that the assumptions concerning the regularity of stable and unstable sets could be reduced to a neighbourhood of x.     

Charm structure functions and gluon shadowing effects with the AdS/CFT model

By means of the UGD function extracted from an AdS/CFT inspired saturation model, the charm and bottom structure functions are studied in fixed-order perturbation theory. It is shown that the theoretical results are in good agreement with the recent HERA data. Then, this UGD function is also used to investigate net-kaon rapidity distribution in Au+Au collisions at RHIC energies and the theoretical results fit well to the BRAHMS data. In the end of this paper, we give the predicted results for nuclear charm structure function at very small x where the popular shadowing parameterizations are invalid.     

Modelling and simulation of a Ka-band DBPSK/DQPSK mobile satellite channel

For the prospective personal satellite communications in the early 21st century, this paper presents a general exploration of a K_a-band DBPSK/DQPSK land-mobile satellite channel model and its BER performance from system design, modelling and simulation. A forward-link (i.e. outbound from the hub) channel design is introduced in brief. A complete model of channel multipath fading and shadowing is proposed for the first time, including a basic model and various derivative submodels corresponding to different actual propagation environments. Computer simulation results are given for a Rician channel model, a shadowed channel model and different combinational-fading channel models by complete curve sets of BER performance, which coincide with the results of the analysis, and could be used as valuable references in further research and implementation.     

Voice frequency change in singers and nonsingers

Trained singers and nonsingers vocally shadowed sequences of rapidly changing tones. Tone changes within the sequences were unpredictable in terms of direction and extent of frequency change. Subjects' responses to the shadowing task could be evaluated for accuracy of frequency matching, and for time and speed of voice frequency change. In addition, subjects' transitions between tones could be classified as hit, overshoot, undershoot, or oscillate. The two groups were equally accurate in matching the pitches of tones comprising the sequences. Similarly, pitch lowering was faster than pitch raising for both groups of subjects, while speeds for both lowering and raising increased with increases in size of the interval between tones. However, singers required less time than nonsingers in effecting transitions, apparently because they achieved faster peak speeds and took more direct paths between tones. Implications of the data for physiological and mechanical aspects of voice frequency control are discussed.     

具有跟踪性质的连续半流

在这篇论文中，我们给出了连续半流的跟踪性质与其逆极限的跟踪性质之间的一些等价条件，并且做为应用，我们证明了具有强跟踪性质的连续半流在其游荡集上的限制也具有强跟踪性质以及连续半流的谱分解定理。     

Shadowing orbits of ordinary differential equations on invariant submanifolds

A finite time shadowing theorem for autonomous ordinary differential equations is presented. Under consideration is the case were there exists a twice continuously differentiable function mapping phase space into with the property that for a particular regular value of the submanifold is invariant under the flow. The main theorem gives a condition which implies that an approximate solution lying close to is uniformly close to a true solution lying in . Applications of this theorem to computer generated approximate orbits are discussed.

     

The Morse spectrum of linear flows on vector bundles

For a linear flow on a vector bundle a spectrum can be defined in the following way: For a chain recurrent component on the projective bundle consider the exponential growth rates associated with (finite time) -chains in , and define the Morse spectrum over as the limits of these growth rates as and . The Morse spectrum of is then the union over all components . This spectrum is a synthesis of the topological approach of Selgrade and Salamon/Zehnder with the spectral concepts based on exponential growth rates, such as the Oseledec spectrum or the dichotomy spectrum of Sacker/Sell. It turns out that contains all Lyapunov exponents of for arbitrary initial values, and the are closed intervals, whose boundary points are actually Lyapunov exponents. Using the fact that is cohomologous to a subflow of a smooth linear flow on a trivial bundle, one can prove integral representations of all Morse and all Lyapunov exponents via smooth ergodic theory. A comparison with other spectral concepts shows that, in general, the Morse spectrum is contained in the topological spectrum and the dichotomy spectrum, but the spectral sets agree if the induced flow on the base space is chain recurrent. However, even in this case, the associated subbundle decompositions of may be finer for the Morse spectrum than for the dynamical spectrum. If one can show that the (closure of the) Floquet spectrum (i.e. the Lyapunov spectrum based on periodic trajectories in ) agrees with the Morse spectrum, then one obtains equality for the Floquet, the entire Oseledec, the Lyapunov, and the Morse spectrum. We present an example (flows induced by vector fields with hyperbolic chain recurrent components on the projective bundle) where this fact can be shown using a version of Bowen's Shadowing Lemma.

     

Symbol error probability evaluation for PSK modulation schemes in generalized non‐Gaussian noise channels

The average symbol error probability (ASEP) performance over the faded radio frequency (RF) link when the noise is additive in nature and has generalized Laplacian distribution is evaluated in this paper. The additive white generalized Laplacian noise (AWGLN) distribution can model different impulsive and non‐Gaussian noise environments often encountered in practice and provides a robust alternative to Gaussian distribution. A new expression for evaluating the exact symbol error probability over a multilevel M‐ary PSK‐modulated AWGLN channel is derived. Based on the obtained expression, the ASEP for the single‐hop RF link that models the shadowing and fading conditions over the RF channel by a generalized –K (GK) distribution is derived. Further, the error performance of a decode‐and‐forward relayed and GK‐distributed two‐hop RF link is discussed, and the results are validated through numerical plots.     

On shadowing property for inverse limit spaces

We study here the G-shadowing property of the shift map σ on the inverse limit space X _f, generated by an equivariant self-map f on a metric G-space X.      

非自治动力系统中周期跟踪和极限跟踪的研究

根据自治动力系统中周期跟踪性和极限跟踪性的定义,将其引入到非自治动力系统。研究了非自治动力系统中周期跟踪性和极限跟踪性的动力学性质,得到：(1)若F={fi}i=0∞拓扑共轭于G={gi}i=0∞,则F具有周期跟踪性当且仅当G具有周期跟踪性;(2)若F={fi}i=0∞拓扑共轭于G={gi}i=0∞,则F具有极限跟踪性当且仅当G具有极限跟踪性;(3)若乘积系统(X×Y,F×G)具有周期跟踪性,则(X,F)和(Y,G)具有周期跟踪性。 以上结论对非自治动力系统中跟踪性的发展有一定的促进作用。