动态接触角的初步分析

应用经典的Moffatt解,通过引入接触线特征参数λ给出接触线上的粘性剪切应力,导出动态接触角和接触线移动速度的关系,尝试解释文献中两种不同测量方法所得静态接触角不一致的现象,理论所揭示的动态接触角和接触线移动速度的关系曲线和以往文献中的曲线形式基本一致,通过和Hoffman试验数据的比较发现,λ与流体性质无关,是表征固壁性质的特征参数,并初步探讨了λ的数理意义。     

垂直对称式平面光栅摄谱仪色散率公式的实验矫正及其在计算机寻找谱线时的应用

本文对垂直对称式平面光栅摄谱仪的线色散率公式(dL/dλ=nf/αcosβ),通过实验矫正应为dL/dλ=2nf/α(cosβ+cosβ~(1/2))。矫正后的线色散率公式可直接用于汇编计算机自动寻找谱线位置的程序。而且程序简单,操作简便(仅输入两个波长值),欲找的谱线位置准确。     

Regio- and stereoselective hydrosilylation of immobilized terminal alkynes

Regio- and stereoselective hydrosilylation of terminal alkynes on solid support using diisopropyl hydrosilanes yielding β-(E)-vinyl silanes with excellent selectivity is reported. The hydrosilylation is catalyzed by Pt(DVDS)/P(ⁱBuNCH₂CH₂)₃N (DVDS = 1,3-divinyl-1,1,3,3-tetramethyl-disiloxane), in which the bulky proazaphosphatrane ligand plays a key role for the selectivity. The immobilized products are characterized with gel phase¹³C NMR and ¹H high resolution magic angle spinning NMR.     

A novel scheme of hyperbolic-end microlens using the arc technology

This study proposes a new scheme of the tapered hyperbolic-end fiber (THEF) by etching the fiber end in a hydrofluoride (HF) solution with a thin layer of oil floating on top of the HF. This study makes it possible to fabricate the hyperbolic microlenses using unique etching and fusion techniques. Compared with previous hemispherical microlenses, the study shows that a THEF with a smaller taper angle and longer taper length fabricated by lower oil density exhibits a smaller radius of curvature, thus resulting in a better coupling efficiency. The THEF microlens results in a more than 2 dB improvement in coupling efficiency when compared with the currently available hemispherical microlenses. The calculation of the effect of oil density in HF etching solution on taper angle and taper length based on an empirical model is in agreement with the measured results. The THEFs have demonstrated up to 86% coupling efficiency for a laser with an aspect ratio of 1:1.5 at a wavelength of 1550 nm.     

Self-adaptive FEM numerical modeling of the mild-slope equation

Based on the linear wave theory, the mild-slope equation (MSE) is a preferred mathematical model to simulate nearshore wave propagation. A numerical model to solve the MSE is developed here on the basis of a self-adaptive finite element model (FEM) combined with an iterative method to determine the wave direction angle to the boundary and thus to improve the treatment of the boundary conditions. The numerical resolution of the waves into ideal domains and multidirectional waves through a breakwater gap shows that the numerical model developed here is effective in representing wave absorption at the absorbing boundaries and can be used to simulate multidirectional wave propagation. Finally, the simulated wave distribution in a real harbor shows that the numerical model can be used for engineering practice.     

Rotation measurement using a circular moiré grating

In this study a non-contact tracker for calculating the angle of rotation of a HMD (head-mounted display) is proposed. The merit of our proposed method is that the computer will change the spatial view to match the user's head posture and keep the ‘immersion' sensation at high accuracy and precision. Our results are validated using moiré fringes as an excellent HMD tracker.     

Total reflection in a uniaxial crystal–uniaxial crystal interface

Considering an interface between two uniaxial birefringent crystals, four reflected and four refracted waves for each incidence direction are obtained. Along this direction can propagate an ordinary wave and an extraordinary wave. Here, we present the analytic expressions for the four critical angles, from which each refracted wave no more exists as propagating wave. We show the variation in these critical angles for different interfaces varying the orientation of the incidence plane with respect to the optical axes. When both principal refractive indices of the second medium are smaller than those of the first medium, then the four critical angles exist for each incidence plane and for any direction of the optical axes. But, when one of the indices has an intermediate value between the values of the indices of the other crystal, we can chose the optical axes directions in such a way that certain critical angles do not exist. Therefore, we can select the refracted wave that is eliminated by total reflection.     

激光窗口热效应对光束发散角的影响

以DF激光器CaF_2输出窗口为例计算了三种输出功率(10~3W,10~4W,10~5W)情况下,窗口材料的温升、波阵面畸变及对光束发散角的影响。计算中窗口直径为40mm,厚度为10mm,光束直径为20mm。     

O2(1Δg)二聚物激光振荡研究

从理论上估算了O2(1Δg)二聚物激光输出功率,在实验中以微波(2.450 GHz)激励高纯氧产生02(1Δg)二聚物,采用平凹稳定谐振腔,首次在波长6561 nm处实现了O2(1Δg)二聚物的激光振荡,当充入氧气压强为133.3 Pa,微波激励功率为600 W时,激光输出功率可达100 μW,此结果在数量级上与理论估算相同.另外还测得激光束散角约37.3 mrad.     

Change of optimum conditions of second harmonic generation of spatial limited laser beams in nonlinear crystals

Frequency doubling of spatially limited laser beams in nonlinear crystals is investigated theoretically. It was shown that the major factor, which reduces the second harmonic generation (SHG) efficiency in this case, is a diaphragm aperture effect, caused by influence of extraordinary polarized laser beams. In that case a spatial shift of mutually orthogonally polarized beams of the incident waves relative to each other in perpendicular direction of wave transmission at the entry to crystals lead to increase the efficiency of SHG of limited beams.