A generalization of Borel's theorem and microlocal Gevrey regularity in involutive structures

In this paper, we use Borel's procedure to construct Gevrey approximate solutions of an initial value problem for involutive systems of Gevrey complex vector fields. As an application, we describe the Gevrey wave-front set of the boundary values of approximate solutions in wedges W of Gevrey involutive structures (M,V). We prove that the Gevrey wave-front set of the boundary value is contained in the polar of a certain cone ΓT(W) contained in RV∩TX where X is a maximally real edge of W. We also prove a partial converse.     

Some blow-up problems for a semilinear parabolic equation with a potential

The blow-up rate estimate for the solution to a semilinear parabolic equation ut=Δu+V(x)|u|^p−1u in Ω×(0,T) with 0-Dirichlet boundary condition is obtained. As an application, it is shown that the asymptotic behavior of blow-up time and blow-up set of the problem with nonnegative initial data u(x,0)=Mφ(x) as M goes to infinity, which have been found in [C. Cortazar, M. Elgueta, J.D. Rossi, The blow-up problem for a semilinear parabolic equation with a potential, preprint, arXiv: math.AP/0607055, July 2006], is improved under some reasonable and weaker conditions compared with [C. Cortazar, M. Elgueta, J.D. Rossi, The blow-up problem for a semilinear parabolic equation with a potential, preprint, arXiv: math.AP/0607055, July 2006].     

Multiplicity of solutions of a zero mass nonlinear equation on a Riemannian manifold

The relation between the number of solutions of a nonlinear equation on a Riemannian manifold and the topology of the manifold itself is studied. The technique is based on Ljusternik-Schnirelmann category and Morse theory.     

求极限的等价无穷大代换

给出等价无穷大代换的法则,并由此得到求某些未定式极限的计算方法.     

The use of phase codes in ultrasound imaging: SNR gain and bandwidth requirements

Most of the literature on coded excitation describes the signal-to-noise ratio gain of a coded waveform in terms of the time-bandwidth product. We have shown that in the context of ultrasound imaging, the expression for the SNR gain provided by matched filtering a coded waveform, can be reduced to the total number of chips in the transmit signal. Hence, the SNR gain is independent of both the bandwidth and the duration of a single-chip. This concept is described in detail, clarifying this seeming contradiction. The impact of bandwidth and pulse duration on the SNR, SNR gain and axial resolution is described. Bandwidth requirements and the impact of regulatory peak-power limitations are also addressed.     

Isotropic Subspaces of Polylinear Forms

The dimensions of maximal isotropic subspaces of symmetric and skew-symmetric forms of degree d in general position are found.     

THE STABILITY IN NEURAL NETWORK WITH DELAY AND DYNAMICAL THRESHOLDEFFECTS

1 IntroductionThe researches on dynamics of neural network systems have been arousinga great deal of interests for more than thirty years. In last ten years, many.researches focused on the study of dynamics of neural network models withdelay. In fact, neural networks often have times delay in reality, for exampledue to the finite switching speed of amplifiers in electronic neural networks.Thus, a large amount of excellent results appeared consecutively [1]--[5]. In thispaper, what we study is…     

Contractibility and Connectedness of Efficient Point Sets

Using the technique of space theory and set-valued analysis, we establish contractibility results for efficient point sets in a locally convex space and a path connectedness result for a positive proper efficient point set in a reflexive space. We also prove a connectedness result for a positive proper efficient point set in a locally convex space; as an application, we give a connectedness result for an efficient solution set in a locally convex space.