自由曲面光学透镜注射成型误差因素研究

自由曲面光学透镜注射成型误差对其光学性能将产生直接影响。注射成型过程中，注射工艺参数组合的优劣，直接影响成型误差的大小。为了获得高精密度的光学元件，就热塑性塑料的注射温度、模具温度、注射压力、保压压力及保压时间等主要工艺参数，对注射成型误差的影响进行综合研究,并且进行了实验验证。研究结果表明：适当提高注射温度与模具温度，同时采用高压注射、高压保压以及快速保压工艺，可显著降低注塑工件的体积收缩率，显著提高面形精密度，其光学表面面形误差小于0.1μm。可为注射工艺设计提供合理的依据。     

CORRECTED SOLVABILITY CONDITIONS FOR NON-LINEAR ASYMMETRIC VIBRATIONS OF A CIRCULAR PLATE

An investigation into non-linear asymmetric vibrations of a clamped circular plate under a harmonic excitation is made. We re-examined a primary resonance studied by Sridhar, Mook and Nayfeh, in which the frequency of excitation is near the natural frequency of an asymmetric mode of the plate. We corrected their solvability conditions and found that in the absence of internal resonance, the steady state response can have not only the form of standing wave but also the form of travelling wave, which is a remarkable contrast to their conclusion.     

CHAOTIC DYNAMICS OF REPEATED IMPACTS IN VIBRATORY BOWL FEEDERS

The vibratory bowl feeder is widely used to convey small engineering parts, and can be considered as a typical non-linear dynamic system experiencing repeated impacts with friction. This paper presents a simplified model and analysis for the dynamic behavior of a single part on the vibrating track of the bowl feeder. While the previous studies are restricted to the sliding regime, the presented analysis is focused on the hopping regime where the high conveying rate is available. The periodic and chaotic regions in the hopping regime are identified through numerical simulation and experimental analysis. It is verified experimentally that the conveying rate in the chaotic region is roughly independent of variations of external parameters. The dynamic effects from the variation of several physical parameters are examined and the important features for the effective design of the vibratory feeder are presented. This research holds much potential for leverage over design problems of a wide range of mechanisms and tools with repeated collisions.     

A GLOBAL MODEL OF POPULATION‐RESOURCE INTERACTION

ABSTRACT. A global model of population‐resource interaction is proposed consisting of two first order ordinary differential equations. In it the population growth rate increases due to increasing technology, then declines due to declining resources. When the model is fit to twentieth century data it predicts that global population will peak and then decline while already declining global resources bottom out; both will eventually stabilize slightly above their lows. Because of the uncertainty of model parameters and resource data, the values and times of these peaks and lows are uncertain, but the qualitative behavior of the model transcends this uncertainty. Actual best‐fit values of population include a peak of nearly nine billion about year 2050 and a peak rate of decline of 0.3% about year 2100. Global resources bottom out at 70% of optimum around year 2100. Variability and sensitivity analyses are also provided.     

嵌碳TiO_2的快速制备及其光催化制氢特性——介绍一个材料综合实验

以TiO_2为代表的半导体光催化剂通过对太阳能的利用,有助于解决当前制约人类社会发展的能源危机与环境污染问题。本实验采用新颖的火焰辅助热解法一步制备出锐钛矿相嵌碳TiO_2微球,该制备方法可避免热处理,实验过程简单快速、无液体废弃物,绿色便捷,利用气相色谱仪测定样品的光催化分解水的产氢量。通过本实验,学生可全面了解半导体光催化剂的光催化原理、制备、表征、功能测试,同时帮助学生认识太阳能、氢能等新能源研究概况,渗透环保的理念。     

有机小分子纳米粒子的光学诊疗应用

癌症严重威胁着人类健康, 因此, 急需开发高效的诊断和治疗方法. 基于光敏剂和近红外激光的光学诊疗将诊断和治疗集于一体, 与传统的手术治疗和化学治疗相比, 光学诊疗显示出无创性和高空间选择性的优点. 有机小分子染料具有确定且易于修饰的化学结构、 良好的重现性和优异的生物相容性, 与无机和聚合物材料相比, 它是一类具有前景的可用于光学诊疗的光敏剂. 本文总结了基于传统小分子染料、 给体-受体(D-A)共轭小分子和聚集诱导发光(AIE)分子等有机小分子的纳米粒子在光学诊疗中的应用. 此外, 对于光学诊疗用有机小分子染料纳米粒子未来的挑战和前景也进行了展望.     

PDL-Compensated Mechanically Induced Long-Period Grating for EDFA Gain Flattening

We present and demonstrate a polarization-insensitive mechanically induced long-period fiber grating (MLPG) for EDFA gain flattening. By forming a 90° fiber rotator in the middle of the MLPG the PDL of the MLPG was substantially reduced. The PDL-compensated MLPG was able to flatten the ASE spectrum of an EDFA successfully without deterioration of the polarization characteristics.     

The X2 Pi and A2 sigma states of FCN+ and ClCN+ : ab initio calculations and simulation of the HeI photoelectron spectra of FCN and ClCN

Geometry optimization and harmonic vibrational frequency calculations at the CASSCF, MP2 and CCSD(T) levels with basis sets up to 6-311G(2df) quality were carried out on the X¹Σ⁺states of FCN and ClCN and the X²Π and A²Σ⁺ states of their cations. Adiabatic ionization energies were calculated up to the CCSD(T)/6-311G(3df)//CCSD(T)/6-311G(2d) level. Some B3LYP calculations were performed also for the ground states of the neutral molecules and the cations. Franck-Condon simulations were performed for the first two bands in the He I photoelectron spectra of FCN and ClCN by employing the ab initio computed geometries and frequencies. By comparing the observed and the simulated spectra obtained from different CN and CX (X = F or Cl) ionic bond lengths chosen on the basis of the ab initio computed values, the following structural parameters are obtained for the two lowest-lying states of FCN⁺ and ClCN⁺ (the method of deriving the uncertainties is described):