不同形貌氮化硅纳米结构的制备与表征

分别通过VLS和VS生长机制得到了Si3N4纳米线和纳米带.产物经X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)等表征手段进行了分析.FTIR图谱表明它们在800～1100cm-1的波数范围内有一个宽的吸收带,这是Si-N键伸缩振动模式的典型吸收带.它们的室温光致发光图谱显示,在420nm左右都有一很强的发射带,表明其将在纳米光电器件中有潜在应用.另外,Si3N4纳米线发光峰与纳米带的发光相比有少许蓝移(蓝移约4nm),这可能和晶须尺寸的少许差别有关.至于纳米带的发光强度大于纳米线的原因,可能是纳米带的比表面积相对较大,有利于悬键的形成,从而导致材料结构内缺陷的浓度较大.     

The limit case response of the archetypal oscillator for smooth and discontinuous dynamics

In this paper, the limit case of the SD (smooth and discontinuous) oscillator is studied. This system exhibits standard dynamics governed by the hyperbolic structure associated with the stationary state of the double-well. The substantial deviation from the standard dynamics is the non-smoothness of the velocity in crossing from one well to another, caused by the loss of local hyperbolicity due to the discontinuity. Without dissipation, the KAM structure on the Poincaré section is constructed with generic KAM curves and a series of fixed points associated with surrounded islands of quasi-periodic orbits and the chaotic connection orbits. It is found that, for a fixed set of parameters, a special chaotic orbit exits there which fills a finite region and connects a series of islands dominated by different chains of fixed points. As one adds weak dissipation, the periodic solutions in this finite region remain unchanged while the quasi-periodic solutions (isolated islands) are converted to the corresponding periodic solutions. The relevant dynamics for the system with weak dissipation under external excitation is shown having period doubling bifurcation leading to chaos, and multi-stable solutions.     

Torsional impact response of a penny-shaped crack in a functional graded strip

The torsional impact response of a penny-shaped crack in a nonhomogeneous strip is considered. The shear modulus is assumed to be functionally graded such that the mathematics is tractable. Laplace and Hankel transforms were used to reduce the problem to solving a Fredholm integral equation. The crack tip stress field is obtained by considering the asymptotic behavior of Bessel function. Explicit expressions of both the dynamic stress intensity factor and the energy density factor were derived. And it is shown that, as crack driving force, they are equivalent for the present crack problem. Investigated are the effects of material nonhomogeneity and strip‘s highness on the dynamic fracture behavior.Numerical results reveal that the peak of the dynamic stress intensity factor can be suppressed by increasing the nonhomogeneity parameter of the shear modulus, and that the dynamic behavior varies little with the adjusting of the strip‘ s highness.     

ON GAUGE EQUIVALENT INTEGRABLE SYSTEMS AND r-MATRICES FOR AKNS HIERARCHY AND A COUPLED MKdV HIERARCHY

IntroductionAmongdifferenteigenvalueproblemsthereexistgaugetransformationswhichcanbeappliedtostudytheinfinite_dimensionalintegrableconstrainedflowproducedbyusingthecertainconstraintsonassociatedeigenvalueproblems[1,2 ] .Morerecently ,integrablefinite_dimensionalsystemsthatadmitaclassicalr_matrixdependingonthespectralproblemshavebeenstudiedextensively[3 ,4] .Buttherearemanyapplicationsofgaugetransformationswhichhavenotbeenstudiedyet.Themainaimofthepresentpaperistointroducesomenewapplicationsoft…     

THE NEW INTEGRABLE SYSTEM OF THE COMPLEX FORM AND THECOUPLED MKDV HIERARCHY

In this paper, the new coupled MKdV hierarchy and their Lsx pairs are oinained,Through introducing a suitable complex form of symplectic structure [5,8], a new integraHe sys-tem of the complex form in the Liouville sense is generated. Moreover, the representations of the solution for the coupled MKdV hierarchy are given by the invohifive solutions of the commutable .     

单位区间图的边泛圈性

本文证明了顶点数至少为４的单位区间图是边泛圈图当且仅当它是３连通的。     

Bifurcations and the penetrating rate analysis of a model for percussive drilling

In this paper, we investigate a low dimensional model of percussive drilling with vibro-impact to mimic the nonlinear dynamics of the bounded progression. Non- holonomity which arises in the stick-slip caused by the impact during drilling fails to be correctly identified via the classical techniques. A reduced model without non-holono- mity is derived by the introduction of a new state variable, of which averaging technique is employed successfully to detect the periodic motions. Local bifurcations are presented directly by using C-L method. Numerical simulations and the penetrating rate analysis along different choices of parame- ters have been carried out to probe the nonlinear behaviour and the optimal penetrating rate of the drilling system.     

COBORDISM CLASSES OF FIBERINGS OVER PRODUCT OF PROJECTIVE SPACES

Let RP（k） denote the k-dimensional real projective space. This article determines which cobordism classes are represented by the total space of a fibering with prescribed base space RP（3）× RP（1）, RP（2） × RP（1）, RP（2）× RP（1）× RP（1） or RP（3）× RP（2）.