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...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。展开更多
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 conta...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.展开更多
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 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.展开更多
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...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.展开更多
文摘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。
基金supported by the National Natural Science Foundation of China(No.61575018)。
文摘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.
基金supported by the National Natural Science Foundation of China(No.61575018)
文摘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.
基金supported by the National Key Research and Development Program of China(No.2018YFB1801003)the National Natural Science Foundation of China(No.61575018)。
文摘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.