响应面法优化木材冻融循环预处理工艺

为提高染液在木材中的渗透性,采用冻融循环法对人工林杉木木材进行预处理,运用响应面法优化预处理工艺条件,通过场发射扫描电镜(FESEM)和压汞法(MIP)分析预处理后木材微观结构的变化。结果表明,冻融循环预处理能明显提高木材的染透率和上染率,且随浸水时间延长、冷冻时间延长、解冻时间增加和循环次数增加呈先增大后降低的趋势,该处理的最优条件是浸水时间24 h、冷冻时间16 h 20 min、解冻时间6 h 41 min、循环2次,此条件下处理材的染透率和上染率分别为54.10%和8.44%,与理论预测值相近;处理后木材细胞的部分纹孔膜破裂或脱落,射线薄壁细胞与轴向管胞的胞间层有裂纹,汞压入总体积和孔隙率增大,表明处理后木材的渗透通道增加,有利于染液在木材中的渗透。

杉木木材酸性染料染色工艺优化

通过正交试验考察染液质量分数、染色时间、染色温度和促染剂用量对染透率、上染率和色差的影响,利用极差分析和方差分析确定各因素的影响程度及各指标的最优工艺参数;在此基础上利用模糊数学综合评判法对3个指标进行综合评价,对染色工艺进一步优化.结果表明:染液质量分数和染色温度对染透率和上染率的影响显著,但各指标单独优化得出的工艺参数不一致;通过模糊数学综合评价获得染透率、上染率和色差效果最优的染色工艺,即染液质量分数2.0%,染色时间4 h,温度90℃,促染剂用量3.0%.在此条件下染透率、上染率和色差分别可达53.64%、7.59%和53.20,总体高于正交试验中各指标最大测试值,说明该方法合理、可行.

Coherence analysis of noise-like pulses generated by an erbium-doped fiber mode-locked laser

The noise-like pulses(NLPs)with tunable fraction of the pedestal height in the whole intensity autocorrelation(AC)trace are numerically demonstrated in the designed erbium-doped fiber(EDF)mode-locked laser,which contains the saturable absorber(SA)with nonlinear polarization rotation(NPR),sinusoidal-shaped or Gaussian-shaped filter,two segments of EDFs,and two pieces of single-mode fibers(SMFs)with normal dispersion and anomalous dispersion,respectively.The pedestal ratio of the intensity AC trace can be tuned by changing the gain saturation energies of EDFs.The results show that when the net cavity dispersion is 1.06 ps^(2),the tuning range of the pedestal ratio for the NLPs can reach its maximum values,which are 0.51—0.89 and 0.58—0.88 for the sinusoidal-shaped and Gaussian-shaped filters,respectively.In addition,an appropriate choice of filter bandwidth is also conducive to obtain a wide range of the tuning pedestal ratio for the intensity AC trace.

大模场面积低正常色散的同轴双芯光纤

为设计具有大模场面积和正常色散的光纤,提出了一种新型的同轴双芯光纤。通过在中心纤芯内引入空气孔,光纤能够拥有红移的零色散波长和提升的有效模场面积。进一步分析了光纤参数对光纤群速度色散和有效模场面积的影响。据此分别设计了具有三种不同参数条件的光纤,光纤具有宽带的正常色散工作区域,可分别覆盖1 400—1 800 nm, 1 700—2 000 nm, 2 000—2 300 nm,具有大于-5 ps/(nm·km)的群速度色散,有效模场面积可高达296μm2。提出的光纤在高功率超短脉冲光纤激光源中具有潜在的应用价值。

Numerical simulation of the heavily Ge-doped polarization-maintaining fiber with normal dispersion

The heavily germanium(Ge)-doped silica fiber assisted by two air holes in the cladding exhibits high nonlinearity and birefringence,low loss and normal group velocity dispersion(GVD)for two fundamental modes(FMs).When the 1920 nm and 0.1 ps pump pulse with 100 kW peak power is coupled into the 0.5-m-long fiber and polarized along one of two principle axes,the generated spectra can cover the wavelength range around 1000—2500 nm at-20 dB.Furthermore,the output pulse has an excellent coherence in the whole wavelength range.

Design of ring-sector-assisted PANDA ring-core few mode fiber

For the PANDA ring-core polarization-maintaining few-mode fiber(RC-PM-FMF)with the given supported eigenmodes,the minimum effective refractive index difference min(Δneff)between the adjacent eigenmodes decreases with the RC size.Consequently,we propose a PANDA RC-PM-FMF assisted by a ring-sector(RS)structure,which can be used to mainly increase theΔneff values between the adjacent even and odd eigenmodes with the same polarization.The RS-RC-PM-FMF with an appropriate choice of the parameters can support 10 linearly polarized(LP)eigenmodes,which have min(Δneff)values higher than 1.9×10^(-4) for the adjacent eigenmodes over the whole C+L band.Furthermore,the fiber is characterized by the low group velocity dispersion(GVD)(-40—20 ps·nm^(-1)·km^(-1))and effective mode areas(63—104μm^(2)),while the total losses are within the range of 0.19—0.23 d B/km over the whole band.