The effect of interstitial air holes on Bragg gratings in photonic crystal fibre (PCF) with a Ge-doped core is numerically investigated by using the beam propagation method (BPM). It is shown that the interstitial air...The effect of interstitial air holes on Bragg gratings in photonic crystal fibre (PCF) with a Ge-doped core is numerically investigated by using the beam propagation method (BPM). It is shown that the interstitial air holes (IAHs) can make Bragg resonance wavelength λ B shift a little towards short wavelengths and increase λ B λ 1 (the wavelength spacing between the main peak with Bragg resonance wavelength λ B and the first side peak with wavelength λ 1 ) and the coupling coefficient κ of Bragg resonance. Moreover, when the ratio of air hole diameter (d) to pitch (Λ), d/Λ, is small, IAHs can suppress the cladding mode resonance. When d/Λ is large, IAHs increase the number of mode that could strongly interact with the fundamental mode. By comparing the transmission spectral characteristics of PCF-based fibre Bragg grating (FBG) with IAHs with those without IAHs at the same air-filling fraction, it is clarified that the change of transmission spectral characteristics of PCF-based FBG with IAHs is not due to a simple change in air-filling fraction. It is also closely related to the distribution of interstitial air holes.展开更多
We have investigated the different optical properties such as confinement loss, waveguide dispersion of a five rings hexagonal photonic crystal fiber under varied air hole diameter (d), lattice pitch (Λ), and air hol...We have investigated the different optical properties such as confinement loss, waveguide dispersion of a five rings hexagonal photonic crystal fiber under varied air hole diameter (d), lattice pitch (Λ), and air hole diameter to lattice pitch ratio for three different materials fused quartz glass, borosilicate glass and sapphire glass. We observed low confinement loss and high negative dispersion at higher d/Λ. Achieving high d/Λ can be done in two ways: increasing the air hole diameter or decreasing the lattice pitch. It has been observed, increasing the air hole diameter has significant effect over reducing lattice pitch in achieving low confinement loss. On the other hand, decreasing the lattice pitch over increasing the air hole diameter has significant effect in achieving high negative dispersion. It has also been found that, effective refractive index (neff) decreases significantly when lattice pitch decreases.展开更多
In the past two decades,numerous large-diameter rock-socketed piles were constructed in China to support foundations of skyscrapers,great bridges or to retain soil in potential geological hazard areas.However,drilling...In the past two decades,numerous large-diameter rock-socketed piles were constructed in China to support foundations of skyscrapers,great bridges or to retain soil in potential geological hazard areas.However,drilling large-diameter rock-socketed pile holes with conventional drilling method such as rotary drilling or cable tool drilling is time-consuming and the cost is usually very high.In order to drill large-diameter rock-socketed pile holes faster at relatively low cost,the FGC15A large-diameter DTH air hammer drilling system was developed in 1987 and was given the second-class award by Ministry of Geology and Mineral Resources in 1991.Since it was innovated the drilling system has been used in more than twenty important and tough projects on land,and wonderful results were acquired.At the same time the large-diameter DTH air hammer drilling system was improved continuously.The FGC15D is the latest version of the technique.展开更多
AIM: To explore an improved procedure involving incomplete fluid-air exchange for idiopathic macular hole(IMH), and the closure rate, visual function, and the visual field of macular holes(MHs) were evaluated.METHODS:...AIM: To explore an improved procedure involving incomplete fluid-air exchange for idiopathic macular hole(IMH), and the closure rate, visual function, and the visual field of macular holes(MHs) were evaluated.METHODS: This prospective randomized controlled study, included 40 eyes of 40 patients with IMH who were treated with pars plana vitrectomy and peeling of the internal limiting membrane. They were grouped by random digital table. Twenty-one eyes underwent incomplete fluidair exchange(IFA) and 19 eyes underwent traditional complete fluid-air exchange(CFA) as the control group. Outcomes included best-corrected visual acuity(BCVA), intraocular pressure, and optical coherence tomography, light adaptive electroretinography, and visual field evaluations.RESULTS: All MHs <400 μm were successfully closed. BCVAs before and 6 mo after surgery were 0.82±0.41 logMAR and 0.28±0.17 logMAR in IFA group and 0.86±0.34 logMAR and 0.34±0.23 logMAR in CFA group, respectively. The electroretinogram analysis of patients in IFA group revealed increases in b-wave amplitudes at 1, 3, and 6 mo after surgery. Additionally, patients in IFA group showed an amplitude increase of 28.6% from baseline at 6 mo(P<0.05), while no obvious improvements were noted in CFA group. Although there were no statistically significant improvements in either group, the IFA group showed a slight increase in mean sensitivity(P>0.05).CONCLUSION: IFA is a reliable method that offers comparable closure rate to CFA and facilitates improvements in visual function.展开更多
基金supported by the National Natural Science Foundation of China (Grant No 10874145)the Yanshan University Doctoral Foundation (Grant No B153)
文摘The effect of interstitial air holes on Bragg gratings in photonic crystal fibre (PCF) with a Ge-doped core is numerically investigated by using the beam propagation method (BPM). It is shown that the interstitial air holes (IAHs) can make Bragg resonance wavelength λ B shift a little towards short wavelengths and increase λ B λ 1 (the wavelength spacing between the main peak with Bragg resonance wavelength λ B and the first side peak with wavelength λ 1 ) and the coupling coefficient κ of Bragg resonance. Moreover, when the ratio of air hole diameter (d) to pitch (Λ), d/Λ, is small, IAHs can suppress the cladding mode resonance. When d/Λ is large, IAHs increase the number of mode that could strongly interact with the fundamental mode. By comparing the transmission spectral characteristics of PCF-based fibre Bragg grating (FBG) with IAHs with those without IAHs at the same air-filling fraction, it is clarified that the change of transmission spectral characteristics of PCF-based FBG with IAHs is not due to a simple change in air-filling fraction. It is also closely related to the distribution of interstitial air holes.
文摘We have investigated the different optical properties such as confinement loss, waveguide dispersion of a five rings hexagonal photonic crystal fiber under varied air hole diameter (d), lattice pitch (Λ), and air hole diameter to lattice pitch ratio for three different materials fused quartz glass, borosilicate glass and sapphire glass. We observed low confinement loss and high negative dispersion at higher d/Λ. Achieving high d/Λ can be done in two ways: increasing the air hole diameter or decreasing the lattice pitch. It has been observed, increasing the air hole diameter has significant effect over reducing lattice pitch in achieving low confinement loss. On the other hand, decreasing the lattice pitch over increasing the air hole diameter has significant effect in achieving high negative dispersion. It has also been found that, effective refractive index (neff) decreases significantly when lattice pitch decreases.
文摘In the past two decades,numerous large-diameter rock-socketed piles were constructed in China to support foundations of skyscrapers,great bridges or to retain soil in potential geological hazard areas.However,drilling large-diameter rock-socketed pile holes with conventional drilling method such as rotary drilling or cable tool drilling is time-consuming and the cost is usually very high.In order to drill large-diameter rock-socketed pile holes faster at relatively low cost,the FGC15A large-diameter DTH air hammer drilling system was developed in 1987 and was given the second-class award by Ministry of Geology and Mineral Resources in 1991.Since it was innovated the drilling system has been used in more than twenty important and tough projects on land,and wonderful results were acquired.At the same time the large-diameter DTH air hammer drilling system was improved continuously.The FGC15D is the latest version of the technique.
基金Supported by National Natural Science Foundation of Xinjiang Autonomous Region, China (No.81460089)
文摘AIM: To explore an improved procedure involving incomplete fluid-air exchange for idiopathic macular hole(IMH), and the closure rate, visual function, and the visual field of macular holes(MHs) were evaluated.METHODS: This prospective randomized controlled study, included 40 eyes of 40 patients with IMH who were treated with pars plana vitrectomy and peeling of the internal limiting membrane. They were grouped by random digital table. Twenty-one eyes underwent incomplete fluidair exchange(IFA) and 19 eyes underwent traditional complete fluid-air exchange(CFA) as the control group. Outcomes included best-corrected visual acuity(BCVA), intraocular pressure, and optical coherence tomography, light adaptive electroretinography, and visual field evaluations.RESULTS: All MHs <400 μm were successfully closed. BCVAs before and 6 mo after surgery were 0.82±0.41 logMAR and 0.28±0.17 logMAR in IFA group and 0.86±0.34 logMAR and 0.34±0.23 logMAR in CFA group, respectively. The electroretinogram analysis of patients in IFA group revealed increases in b-wave amplitudes at 1, 3, and 6 mo after surgery. Additionally, patients in IFA group showed an amplitude increase of 28.6% from baseline at 6 mo(P<0.05), while no obvious improvements were noted in CFA group. Although there were no statistically significant improvements in either group, the IFA group showed a slight increase in mean sensitivity(P>0.05).CONCLUSION: IFA is a reliable method that offers comparable closure rate to CFA and facilitates improvements in visual function.
