A dynamical theory for the off-shell continuation of the πNt-matrix

A dynamical theory, based on analyticity and dispersion theory, for the half-off-shell continuation of the on-shell πNt-matrix is proposed and developed. The resulting half-shell t-matrix is covariant, unitary, crossing symmetric, and based on a field-theoretic foundation. The dynamical information required to continue half off shell is obtained from field theory and consists of the off-shell amplitudes corresponding to the exchanges of the nucleon in the s- and u-channels and the ? and σ mesons in the t-channel. A coupled system of integral equations is derived for the partial wave half-shell t-matrix, which is truncated at the S- and P-waves and solved numerically. The results are compared with those obtained from various separable models of the πNt-matrix. The half-shell t-matrix is examined for separability and is found to be approximately separable in the P₃₃ and P₃₁ states. The dynamical content of the half-shell t-matrix is further illustrated by modeling the dynamical equation.     

截止阀启闭过程内部瞬态流动特性

为分析截止阀启闭过程内部的瞬态流动特性,基于N-S方程和标准的κ-ε湍流模型,通过自定义函数(UDF)和C++语言编程给定阀芯的运动规律,采用动网格技术对截止阀进行了瞬态的全三维湍流数值模拟,得到阀芯在不同运动时刻的瞬态流场,阀芯在运动过程中受到的流体挤压效应是影响截止阀性能的主要原因。截止阀瞬态的全三维数值研究具有较高的可靠性,数值结果为进一步研究截止阀的性能提供重要理论依据。     

A fundamental theory of the half-shell t-matrix for nucleon-nucleon scattering

A dispersion-theoretic approach to the half-shell t-matrix is presented and applied to the ¹S₀- and ¹P₁-Reid interactions. This approach is shown to provide interesting dynamical insights about these half-shell t-matrices.     

Two-body T-matrix continued off the energy shell

A generalized parametrization scheme, which treats both half-shell and off-shell scattering on equal footing, is derived for the two-particle transition operator. The appropriate theory in respect of this is developed by using a wave function approach to off-shell scattering and the computational procedure to be followed is demonstrated by means of a model calculation.     

二次谐波共焦成像的分辨率

通过与双光子荧光共焦成像过程比较,研究了非线性二次谐波的强度脉冲响应函数并对它进行频域分析,获得了横向、纵向截止频率和通频带.研究结果表明：二次谐波共焦成像具有更高的分辨率.     

不同荧光波长的双光子共焦成像分析

研究了双光子共焦显微镜中不同荧光波长对成像特性的影响,导出了不同荧光波长的三维脉冲响应函数和三维光学传递函数并进行数值计算.研究结果表明：不同荧光波长对双光子共焦显微镜的三维光学传递函数、三维脉冲响应函数和空间截止频率产生明显的影响,随着荧光波长的增大,分辨率明显下降,但不会出现单光子共焦显微镜中的失锥现象,选取适当的荧光波长进行成像,有利于进一步改善图像分辨率和成像质量.     

Hulthén off-shell transition matrix for nuclear systems

Exact analytical expression for the Hulthén off-shell Jost solution is constructed by using the particular integral of the inhomogeneous Schrödinger equation. The Jost solution is exploited to calculate the off-shell physical solution and in turn the off-shell T-matrix. The off-shell T-matrices are computed for the (n-p) and (n-d) systems and are found in order with respect to its half-shell behavior.     

Magnetic field modulation of photonic bandgap on FeCo/NiO half-shell array

FeCo/NiO half-shell arrays were fabricated based on the periodic monolayer polystyrene spheres. The two-dimensional magnetic periodic arrays form well-defined photonic crystals with pronounced stop bands. Quite interestingly, it is found that the stop bands can be tuned by an external magnetic field. The underlying mechanism is attributed to the controllable dielectric constant of the magnetic FeCo film under an applied magnetic field. The results shown here may open up an avenue for magnetically tunable photonic crystal stop bands, which may be useful for the creation of new magneto-optical devices.     

Derivation of Gamow Vectors for Resonances in Cut-Off Potentials

Gamow vectors are rigourously derived for a realistic case including an infinite number of resonant poles. This is the case of resonances produced by cut-off potentials. These are three-dimensional spherically symmetric potentials which vanish outside a bounded region. We solely consider the case of particles without internal structure and work with l = 0.     

半壳结构金纳米膜的局域表面等离子体共振效应

采用纳米模版印刷术和化学自组装技术制备了半壳结构的金粒子膜.利用场发射扫描电子显微镜和光谱仪等测试手段对样品的结构和光学性质进行了分析.研究发现，该结构的金膜所具有独特的局域表面等离子体共振效应取决于样品的粒子大小、间距等微观结构，且其峰值吸收波长对其周围环境介质的介电常数变化十分敏感.实验结果表明，粒子排列均匀的亚单层膜结构是控制光学性质稳定的关键. 关键词： 局域表面等离子体共振 半壳结构 纳米模版印刷术     

Half-shellT matrix for Coulomb-modified Graz separable potential

We construct a closed form expression for the off-shell Jost function for scattering by the Coulomb-distorted Graz separable potential and express it in the ‘maximal reduced form’. Our result is particularly suitable for numerical computation. We present a case study in support of this and examine the role of Coulomb interaction in thep — p half-shell scattering in the¹ S ₀ channel.     

Proton-proton scattering without Coulomb force renormalization

We demonstrate numerically that proton-proton (pp scattering observables can be determined directly by standard short-range methods using a screened pp Coulomb force without renormalization. In the examples the appropriate screening radii are given. We also numerically investigate solutions of the 3-dimensional Lippmann-Schwinger (LS) equation for a screened Coulomb potential alone in the limit of large screening radii and confirm analytically predicted properties for off-shell, half-shell and on-shell Coulomb t -matrices. These 3-dimensional solutions will form a basis for a novel approach to include the pp Coulomb interaction into the 3N Faddeev framework.     

Long-wavelength behavior of the optimal HNC/0 solution for the ground state

The ground-state wave function for a two-dimensional homogeneous liquid⁴He at zero temperature is obtained from a paired-phonon analysis within the HNC/0 approximation. The long-wavelength behavior of the two-body correlation factor,u(q), is studied by following the procedure previously applied to three-dimensional bulk systems. It is shown that a cut-off law for the phonons can be determined by analyzingu(q) at small two-dimensional momentaq. The numerical results strongly support an exponential cut-off similar to that suggested by Chester and Reatto for the bulk liquid. The first-sound velocityc ₁ and the cut-off momentumq _c are calculated at several densities in the range 0.028–0.080 Å^–2.     

On the analytic properties of non-relativistic two-body off-shell amplitudes: (I). Spectral function methods

Spectral function methods introduced in field theoretic schemes, are used for the study of nonrelativistic two-body off-shell amplitudes taken in a l-wave and generated by Yukawa-type interactions. The analytic properties of the basic components of such amplitudes are specified in a detailed way, which can provide a useful guide line for their parametrisations. Related integral equations are also examined, as well as some discrepancies with independent results concerning the half-shell case. The connections of such an approach with other r- and p-space formalisms are fully recognised in paper II, in which further unitary representations related with this analysis, are also considered.     

Parity violating vacuum currents on the random lattice

The Dirac operator is studied both with and without background gauge fieldson a three-dimensional random lattice. It is shown that the correct continuum limit for free fermions is recovered in the zero field case and the doubling problem evaded at tree level, the doubles acquiring masses of order the cut-off and decoupling from long-distance physics. The vacuum current is calculated in the presence of a nontrivial U(1) field and shown to be in agreement with continuum calculations.     

强激光场中模型氢原子和真实氢原子产生高次谐波的比较

通过数值求解原子在强激光场中的含时薛定谔方程,研究了有库仑奇点和无库仑奇点的一维模型氢原子和三维真实氢原子产生高次谐波的特性。结果表明,有库仑奇点和无库仑奇点的一维模型氢原子和三维真实氢原子产生高次谐波的截止位置相同,但是高次谐波强度变化特征明显不同,进一步的研究表明,无库仑奇点的模型氢原子产生的高次谐波谱相对变化趋势与三维真实氢原子的高次谐波谱变化趋势是完全一致的。     

强激光场中模型氢原子和真实氢原子产生高次谐波的比较

通过数值求解原子在强激光场中的含时薛定谔方程,研究了有库仑奇点和无库仑奇点的一维模型氢原子和三维真实氢原子产生高次谐波的特性.结果表明,有库仑奇点和无库仑奇点的一维模型氢原子和三维真实氢原子产生高次谐波的截止位置相同,但是高次谐波强度变化特征明显不同,进一步的研究表明,无库仑奇点的模型氢原子产生的高次谐波谱相对变化趋势与三维真实氢原子的高次谐波谱变化趋势是完全一致的.     

大间隙速调管放大器中二极管寄生振荡及其抑制

利用三维高频电磁软件和三维粒子模拟软件,对大间隙强流相对论速调管放大器中的二极管寄生振荡机制进行了模拟研究,发现由于6.18 GHz频点的高阶TM31模式在二极管区截止,故形成了谐振腔结构,进而对电子束产生强烈的调制,干扰了速调管的正常工作。结合模拟结果,提出了优化和改进措施。粒子模拟结果表明:二极管结构改进后,寄生振荡消失,束流调制效果得到显著改善。