In order to predict acoustic radiation from a structure in waveguide, a method based on wave superposition is proposed, in which the free-space Green＇s function is used to match the strength of equivalent sources. In...In order to predict acoustic radiation from a structure in waveguide, a method based on wave superposition is proposed, in which the free-space Green＇s function is used to match the strength of equivalent sources. In addition, in order to neglect the effect of sound reflection from boundaries, necessary treatment is conducted, which makes the method more efficient. Moreover, this method is combined with the sound propagation algorithms to predict the sound radiated from a cylindrical shell in waveguide. Numerical simulations show the effect of how reflections can be neglected if the distance between the structure and the boundary exceeds the maximum linear dimension of the structure. It also shows that the reflection from the bottom of the waveguide can be approximated by plane wave conditionally. The proposed method is more robust and efficient in computation, which can be used to predict the acoustic radiation in waveguide.展开更多
The aim of the research is to determine the capillary conductivity coefficient as a characteristic material moisture parameter of the building materials using a non-destructive method while using microwave radiation. ...The aim of the research is to determine the capillary conductivity coefficient as a characteristic material moisture parameter of the building materials using a non-destructive method while using microwave radiation. Available documents are usually focused on the description of diffusion and similar works are based on the difference of partial pressure [I]. Publication will introduce experimental measurements the transport of humidity in porous material in a non-stationary state. As a result may be obtaining of data for formulation of humidity profiles with the help of experimentally built measuring apparatus without influence of human factor. Aim is verification of mentioned method of measurement for description of moisture parameters building materials applicable for practice. Complication in the determination of moisture parameters is various porous textures and the remains effect of condensation and transport influence of liquid moisture by diffusion in porous material. At the present time does not exist for standard use computational theory to description of transport of dampness in building materials. Moisture in porous medium is transported by the help of the capillary forces. The liquid moisture gradient is an indicator of moving of liquid moisture in a porous material through capillaries. This phenomenon is called capillary conductivity of moisture. Purpose presents measurement of material specimen for formulation of capillary conductivity coefficient and its dependence on moisture. The specimen of porous material is subjected to an isothermal moisture intake process. The transient moisture distribution in the specimen during the process is determined, at different stages of the process. Methodology of data scanning with the help of microwave radiation and data processing is processed for numerical computation on the basis known physics laws. The outputs of measurements can be used for evaluation of physical properties of building materials.展开更多
The spontaneous emission(SE) of Er3+ embedded in a double slot dielectric structure was studied by a quantum-electrodynamical formalism. The study shows that the slot width and the position of Er3+ in slot structure h...The spontaneous emission(SE) of Er3+ embedded in a double slot dielectric structure was studied by a quantum-electrodynamical formalism. The study shows that the slot width and the position of Er3+ in slot structure have a significant effect on the SE. The double slot waveguides were fabricated by embedding two low-index Er/Yb silicate material layers into high-index silicon. The radiative efficiency of Er3+ in the double slot waveguides is found to be higher than that of the single slot waveguide, which is consistent with the theory simulation. The 0.67 d B signal enhancement at 1.53 ?m in a 4.6-mm-long slot waveguide was observed pumped by 1476 nm laser. These results show the relevance of our model to study the SE processes in multilayer structures and are important for future realization of silicon-compatible active optical devices.展开更多
基金Foundation item： Supported by the National Natural Science Foundation of China under Grant No. 11274080, and the Young Scientists Fund of the National Natural Science Foundation of China under Grant No. 11404313.
文摘In order to predict acoustic radiation from a structure in waveguide, a method based on wave superposition is proposed, in which the free-space Green＇s function is used to match the strength of equivalent sources. In addition, in order to neglect the effect of sound reflection from boundaries, necessary treatment is conducted, which makes the method more efficient. Moreover, this method is combined with the sound propagation algorithms to predict the sound radiated from a cylindrical shell in waveguide. Numerical simulations show the effect of how reflections can be neglected if the distance between the structure and the boundary exceeds the maximum linear dimension of the structure. It also shows that the reflection from the bottom of the waveguide can be approximated by plane wave conditionally. The proposed method is more robust and efficient in computation, which can be used to predict the acoustic radiation in waveguide.
文摘The aim of the research is to determine the capillary conductivity coefficient as a characteristic material moisture parameter of the building materials using a non-destructive method while using microwave radiation. Available documents are usually focused on the description of diffusion and similar works are based on the difference of partial pressure [I]. Publication will introduce experimental measurements the transport of humidity in porous material in a non-stationary state. As a result may be obtaining of data for formulation of humidity profiles with the help of experimentally built measuring apparatus without influence of human factor. Aim is verification of mentioned method of measurement for description of moisture parameters building materials applicable for practice. Complication in the determination of moisture parameters is various porous textures and the remains effect of condensation and transport influence of liquid moisture by diffusion in porous material. At the present time does not exist for standard use computational theory to description of transport of dampness in building materials. Moisture in porous medium is transported by the help of the capillary forces. The liquid moisture gradient is an indicator of moving of liquid moisture in a porous material through capillaries. This phenomenon is called capillary conductivity of moisture. Purpose presents measurement of material specimen for formulation of capillary conductivity coefficient and its dependence on moisture. The specimen of porous material is subjected to an isothermal moisture intake process. The transient moisture distribution in the specimen during the process is determined, at different stages of the process. Methodology of data scanning with the help of microwave radiation and data processing is processed for numerical computation on the basis known physics laws. The outputs of measurements can be used for evaluation of physical properties of building materials.
基金supported by the National Natural Science Foundation of China(Grant Nos.61377056 and 61320106001)the Program for New Century Excellent Talents in University
文摘The spontaneous emission(SE) of Er3+ embedded in a double slot dielectric structure was studied by a quantum-electrodynamical formalism. The study shows that the slot width and the position of Er3+ in slot structure have a significant effect on the SE. The double slot waveguides were fabricated by embedding two low-index Er/Yb silicate material layers into high-index silicon. The radiative efficiency of Er3+ in the double slot waveguides is found to be higher than that of the single slot waveguide, which is consistent with the theory simulation. The 0.67 d B signal enhancement at 1.53 ?m in a 4.6-mm-long slot waveguide was observed pumped by 1476 nm laser. These results show the relevance of our model to study the SE processes in multilayer structures and are important for future realization of silicon-compatible active optical devices.
