磁性排斥实验研究

本文介绍了两种不同的磁性排斥实验方法。验证了磁力与两磁铁间距离平方成反比的关系。并为大学物理实验及演示实验推荐了有参考价值的实验装置。     

Discontinuity of NRD-Guide and Its Application in Millimeter Wave Circuits

In this paper, the performances of two typical discontinuous structures of the NRD-guide, the traverse metallic rod to disturb an incident wave and the traverse probe to excite required modes, are analyzed and computed by utilizing the theory of modes orthogonality of the NRD-guide. The moment method is used to evaluate the current distribution on the rod and probe and the affection of some higher-order modes is taken into account simultaneously. On these bases, the multitone exciting steady states of two kinds of important circuits that employ the above discontinuous structures, the NRD-guide crossbar balanced mixer and the LSM ₁₁ ⁰ -mode oscillator, are simulated by the harmonic balance technique based on the multi-dimensional discrete Fourier transformation (MDFT-HB method).     

MISSED OPPORTUNITIES IN NATURAL RESOURCE MANAGEMENT

After 20 years of effort, technical approaches to natural resource management have not been effective in preventing overuse and destruction of resources. The resource modeling community can help to change our present course toward destruction by (1) recognizing and publicizing the ineffectiveness of scientific, technical and magical approaches to resource management, (2) pointing out that the resolution of environmental problems is impossible unless the social problems of excessive human population sizes and excessive consumption are effectively addressed, (3) making clear the irrationality and imprudence of current environmental decisionmaking under uncertainty, and (4) pointing out the impossibility of achieving conservation goals by management that attempts to achieve economic optima.     

Role of metastable states in circumventing laser pulse jitters in multi-step laser excitation experiments

The role of metastable states in circumventing laser pulse jitters in multi-step laser excitation of high-lying Rydberg and autoionizing states is discussed. A case study is presented where step-wise excitation of 3d4d ³G_3,4,5 states of Ca is achieved despite a large jitter between the laser pulses.     

B?cklund transformation and multiple soliton solutions for the (3+1)-dimensional Jimbo-Miwa equation

We study an approach to constructing multiple soliton solutions of the (3+1)-dimensional nonlinear evolution equation. We take the (3+1)-dimensional Jimbo－Miwa (JM) equation as an example. Using the extended homogeneous balance method, one can find a B?cklund transformation to decompose the (3+1)-dimensional JM equation into a linear partial differential equation and two bilinear partial differential equations. Starting from these linear and bilinear partial differential equations, some multiple soliton solutions for the (3+1)-dimensional JM equation are obtained by introducing a class of formal solutions.     

验光中的双眼平衡

验光后应进行双眼平衡检验，但一般仅将它理解为视力平衡。本文论述了视力平衡、光焦度平衡和双眼像平衡三种平衡及其相互关系，并提出一种新的散光眼像平衡的估算方法。     

Positivity and Stability for a Population Equation with Diffusion on 1

Using positivity, abstract extrapolation spaces, and a generalization of the Jörgens–Vidav-Voigt perturbation theorem for the essential spectral radius of strongly continuous semigroups given in [19], we study the asymptotic behavior of a linear age-dependent population problem with spatial diffusion where the birth and the death rates depend on the spatial variable.     

两个非线性发展方程的双向孤波解与孤子解

采用分步确定拟解的原则, 对齐次平衡法求非线性发展方程孤子解的关键步骤作了进一步改 进. 以广义Boussinesq方程和bidirectional Kaup-Kupershmidt方程为应用实例, 说明使用 该方法可有效避免“中间表达式膨胀”的问题, 除获得标准Hirota形式的孤子解外, 还能获 得其他形式的孤子解. 关键词： 齐次平衡法 孤子解 孤波解 广义Boussinesq方程 bidirectional Kaup-Kupershmi dt方程