Eigenvibrations in trapped-energy contoured piezoelectric resonators with a one-sided arbitrarily oriented elliptical convexity

A mathematical model of a piezoelectric plate is discussed with a one-sided convex surface of an arbitrary shape. Generic relations are given to calculate the frequency spectrum and distributions of the vibration amplitudes with normal drive levels. A particular case of the ellipsoidal convexity is studied, that is arbitrarily oriented with respect to the plate axes. A numerical example for such a curvature is also given. Based upon this, we show that the frequency spectrum is critically dependent on the angle between the main ellipsoid axis and the rotated coordinates of a piezoelectric plate and to the ratio of the main radii of an ellipsoid. We notice that such a surface allows for a proper placement of the anharmonics in the frequency spectrum, avoiding their interaction caused by environment. It may also be useful to model the manufacturing imperfection and its influence upon the vibration spectra.     

Zeros of the helicity amplitudes of Σ+-p elastic scattering

Optimally exploiting the analytic structure of the helicity amplitudes of Σ⁺-p scattering we locate their zeros by making a fit to the differential cross-section curves at 40, 100 and 150 MeV energies. Minute changes in the positions of the zeros produced detectable noises in the fit. It was observed that quite reliable predictions for the phase shifts can also be obtained from this analysis.     

微极热弹性无限板的轴对称自由振动

研究了在应力自由和刚性固定边界条件下,无能量耗散的均匀、各向同性微极热弹性无限板的轴对称自由振动波的传播,导出了相应的对称和斜对称模态波传播的闭合式特征方程和不同区域的特征方程.对短波的情况,应力自由热绝缘和等温板中对称和斜对称模态波传播的特征方程退化为Rayleigh表面波频率方程.根据导出的特征方程得到了热弹性、微极弹性和弹性板的结果.在对称和斜对称运动中计算了板的位移分量幅值、微转动幅值和温度分布,给出了对称和斜对称模式的频散曲线,并示出了位移分量和微转动幅值和温度分布的曲线.能够发现理论分析和数值结论是非常一致的.     

Phase-function method for velocity-dependent potentials

We have adapted the phase-function method for studying on- and off-shell properties of velocity-dependent potentials. The main result presented in this paper is an ansatz for the interpolatingT-matrix function (on- or off- the energy-shell as the case may). Based on this ansatz we have presented an efficient method for computing the off-shell extension function which plays a role in the theories of three particle system. We have demonstrated this by means of a model calculation.     

New sum rules forππ scattering using Roskies’ amplitudes

On the basis of crossing symmetry a new set of exact relations involving theππ partial wave amplitudes have been derived, using Roskies’ amplitudes.     

Mean amplitudes of vibration of molecules and ions with interhalogen bonds and related species

Mean amplitudes of vibration of molecules and ions containing interhalogen bonds are reviewed and critically analyzed. The presented information comprises pure interhalogen compounds as well as oxohalides. Correlations between mean amplitude values and structural and bond properties are discussed. Comparisons with data of related - specially isoelectronic - species are also performed. Characteristic ranges for the mean amplitudes of vibration for halogen-halogen and halogen-oxygen bonds could be established. The presented and discussed results are also of central importance for the analysis and interpretation of electron diffraction studies.     

The Structure of S Pair in Collective States (Ⅰ)

A new S pair and seniority particle operator used to overcome the difficulties due to seniority mixing are defined in collective motion of nuclei. The structure amplitude of S pair is determined in a self-consistent manner.     

Structure of D Pair in Collective States of Nuclei

As a successive work a modified D pair independent of the S pair treated in our previous papers is introduced to avoid the seniority mixing problem. The structure amplitudes of this D pair and S pair are determined simultaneously and self-consistently by iteration.     

Partial Wave Analysis of J/ψ Decays into ρρπ

The possible place to search for exotic states in J/ψ hadronic decays is in J/ψ→ρρπ. Because of the symmetry of identical particle and the symmetry of isospin, the physical analysis on this channel is quite complicated. In this paper, the method to use the partial wave analysis based on covariant helicity amplitude analysis to study the invariant mass spectrum of ρπ and to find the evidence of exotic states in ρπ spectrum is discussed. The decay amplitude for the decay sequence J/ψ→ρX, X →ρπ is given first. Then we discuss how to realize the identical particle symmetry and the isospin symmetry in the decay amplitude, which is the key point in the analysis of this channel. Then the total decay amplitude of this channel including all decay components is given. After that, how to identify the exotic states in the ρπ spectrum is discussed. What is discussed in this paper is the theoretical basis on experimentally searching for exotic states at BEPC/BES.     

Control of Combustion Oscillations Close to Stoichiometry

The oscillations that occur in ducted plane and round sudden-expansions with combustion of premixed air and methane have been examined for flow conditions which gave rise to large amplitudes corresponding to half-waves. They were present above a minimum flow rate and in a range of equivalence ratios that increased slightly with flow rate and centred around stoichiometry. The periodic roll-up, growth and collapse of combusting vortices downstream of the plane expansion was examined in terms of chemiluminescence images and velocity and temperature measurements synchronised with the pressure oscillation. The periodic heat release and pressure fluctuations were shown to be in phase close to the geometric axis, with the oscillations driven in this region, so that local perturbations were likely to have greatest effect when introduced there. The pressure signals in both ducts were similar so that the flow in the round duct was expected to behave in the same way and, a stream of pulsed methane was thus best able to modify the oscillations when introduced on the axis and close to the expansion plane. Low-frequency oscillations tended to modulate the half-wave with effects that increased with flow rate and, therefore, heat release rate, and stemmed from a combination of the bulk-mode resonance of the upstream cavity and high strain rate in the vicinity of the expansion. The amplitudes of the oscillations in the round duct were controlled by imposing oscillations on the pressure field and heat release at a phase or frequency different from that of the combustion oscillations. Both approaches led to substantial reduction in the amplitude of oscillations at low flow rates, when the modulations were small, but the effectiveness of control deteriorated sharply at the higher flow rates. This revised version was published online in July 2006 with corrections to the Cover Date.