The effect of irradiation on the strain sensitivity coefficient of strain sensing fiber Bragg gratings （FBGs） has been investigated through experiments. FBGs were fabricated in single mode fibers with 3 tool% Ge-con...The effect of irradiation on the strain sensitivity coefficient of strain sensing fiber Bragg gratings （FBGs） has been investigated through experiments. FBGs were fabricated in single mode fibers with 3 tool% Ge-concentration in the core and with a H2-1oading treatment. In experiments, the FBGs were subjected to y-radiation exposures using a Co6~ source at a dose-rate of 25 Gy/min up to a total dose of 10.5 kGy. The GeO defect in fiber absorbs photons to form a GeE＇ defect; the interaction with H2 is a probable reason for the y-radiation sensitivity of gratings written in hydrogen loaded fibres, The effect mechanism of radiation on the strain sensitivity coefficient is similar to that of radiation on the temperature sensitivity coefficient. Radiation affects the effective index neff, which results in the change of the thermo-optic coefficient and the strain-optic coefficient. Irradiation can change the strain sensitivity coefficient of FBGs by 1.48%-2.71%, as well as changing the Bragg wavelength shift （BWS） by 22 pm-25 pm under a total dose of 10.5 kGy. Our research demonstrates that the effect of irradiation on the strain sensitivity coefficient of FBG is small and that strain sensing FBGs can work well in the radiation environment.展开更多
This paper is concerned with a study of wave propagation due to scattering of an obliquely incident wave by a porous vertical plate with nonuniform porosity which is completely submerged in water of finite depth.The p...This paper is concerned with a study of wave propagation due to scattering of an obliquely incident wave by a porous vertical plate with nonuniform porosity which is completely submerged in water of finite depth.The problem is formulated in terms of a Fredholm integral equation of the second kind in difference in potential across the barrier.The integral equation is then solved using two methods:the boundary element method and the collocation method.The reflection coefficients,transmission coefficient,and amount of energy dissipation are evaluated using the solution of the integral equation.It is observed that non-uniform porosity of a barrier has significant effect on the reflection of waves and energy dissipation compared to a barrier with uniform porosity.The dissipation of the wave energy by a non-uniform porous barrier can be enhanced and can be made larger than that of a barrier with uniform porosity,by suitable choice of non-uniform porosity distribution in the barrier.This has an important bearing on reducing the wave power and thereby protecting the shore line from coastal erosion.Also,an obliquely incident wave reduces reflection and dissipation while increasing transmission of wave energy as compared to a normally incident wave.展开更多
In order to increase the evaluating precision of mesh reflection wave, the mesh wave impedance (MWI) is extended to the non-uniform mesh in 1-D and 2-D cases for the first time on the basis of the Yee's positional...In order to increase the evaluating precision of mesh reflection wave, the mesh wave impedance (MWI) is extended to the non-uniform mesh in 1-D and 2-D cases for the first time on the basis of the Yee's positional relation for electromagnetic field components. Lots of characteristics are obtained for different mesh sizes and frequencies. Then the reflection coefficient caused by the non-uniform mesh can be calculated according to the theory of equivalent transmission line. By comparing it with that calculated by MWI in the uniform mesh, it is found that the evaluating error can be largely reduced and is in good agreement with that directly computed by FDTD method. And this extension of MWI can be used in the error analysis of complex mesh.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61007040)
文摘The effect of irradiation on the strain sensitivity coefficient of strain sensing fiber Bragg gratings （FBGs） has been investigated through experiments. FBGs were fabricated in single mode fibers with 3 tool% Ge-concentration in the core and with a H2-1oading treatment. In experiments, the FBGs were subjected to y-radiation exposures using a Co6~ source at a dose-rate of 25 Gy/min up to a total dose of 10.5 kGy. The GeO defect in fiber absorbs photons to form a GeE＇ defect; the interaction with H2 is a probable reason for the y-radiation sensitivity of gratings written in hydrogen loaded fibres, The effect mechanism of radiation on the strain sensitivity coefficient is similar to that of radiation on the temperature sensitivity coefficient. Radiation affects the effective index neff, which results in the change of the thermo-optic coefficient and the strain-optic coefficient. Irradiation can change the strain sensitivity coefficient of FBGs by 1.48%-2.71%, as well as changing the Bragg wavelength shift （BWS） by 22 pm-25 pm under a total dose of 10.5 kGy. Our research demonstrates that the effect of irradiation on the strain sensitivity coefficient of FBG is small and that strain sensing FBGs can work well in the radiation environment.
基金partially supported by SVMCM scholarship No.WBP211645525952 by Government of West Bengal,India,through Shreya Banerjee.
文摘This paper is concerned with a study of wave propagation due to scattering of an obliquely incident wave by a porous vertical plate with nonuniform porosity which is completely submerged in water of finite depth.The problem is formulated in terms of a Fredholm integral equation of the second kind in difference in potential across the barrier.The integral equation is then solved using two methods:the boundary element method and the collocation method.The reflection coefficients,transmission coefficient,and amount of energy dissipation are evaluated using the solution of the integral equation.It is observed that non-uniform porosity of a barrier has significant effect on the reflection of waves and energy dissipation compared to a barrier with uniform porosity.The dissipation of the wave energy by a non-uniform porous barrier can be enhanced and can be made larger than that of a barrier with uniform porosity,by suitable choice of non-uniform porosity distribution in the barrier.This has an important bearing on reducing the wave power and thereby protecting the shore line from coastal erosion.Also,an obliquely incident wave reduces reflection and dissipation while increasing transmission of wave energy as compared to a normally incident wave.
文摘In order to increase the evaluating precision of mesh reflection wave, the mesh wave impedance (MWI) is extended to the non-uniform mesh in 1-D and 2-D cases for the first time on the basis of the Yee's positional relation for electromagnetic field components. Lots of characteristics are obtained for different mesh sizes and frequencies. Then the reflection coefficient caused by the non-uniform mesh can be calculated according to the theory of equivalent transmission line. By comparing it with that calculated by MWI in the uniform mesh, it is found that the evaluating error can be largely reduced and is in good agreement with that directly computed by FDTD method. And this extension of MWI can be used in the error analysis of complex mesh.
