Many countries which seek to understand the acoustic performance of railway noise barriers have established standards for the conduct of in-situ experiments.However,there are no universally acknowledged receiver posit...Many countries which seek to understand the acoustic performance of railway noise barriers have established standards for the conduct of in-situ experiments.However,there are no universally acknowledged receiver positions for the evaluation of the barrier performance,a fact which may be leading to uncertainty over the noise reduction capabilities of available barriers.In terms of the descriptor of the barrier performance,the general recommendation is the A-weighted sound pressure level,although the latter is considered to underestimate low frequencies for railway noise barrier.Thus,in this study,the comparison of receiver positions and the descriptors among existing Chinese,ISO and European standards were investigated.Based upon a combination of diffraction theory and standards,a rearrangement of receiver positions and one-third-octave-band analysis were proposed.In addition,in line with improved methods,an in-situ measurement of insertion loss for a 1.5 mhigh railway noise barrier was designed and conducted.The results of the experiment validate as effective and applicable the new receiver positions.These results also suggest that one-third-octave-band analysis is indispensable.展开更多
Fiber Fabry-Perot (FFP) filters have been widely used in optical fiber communications, and insertion loss (IL) is one of its important characteristics. Based on theoretically analysis, factors related to IL were discu...Fiber Fabry-Perot (FFP) filters have been widely used in optical fiber communications, and insertion loss (IL) is one of its important characteristics. Based on theoretically analysis, factors related to IL were discussed. In order to investigate the IL of different structures, simulations are carried out with finite-difference time-domain (FDTD) algorithm. Comparisons are made between the optimized structure and full-size-mirror FFP filter, and fiber-inserted FFP filter as well. Simulation results demonstrated that the finite- size-mirror structure can confine the mode size of the open resonator, hence reduce the IL of FFP filter.展开更多
Insertion loss （IL） is one of the important parameters of asymmetrical digital subscriber loop （ADSL） transformers. In different frequency bands, the factors that affect insertion loss are different. Windings main...Insertion loss （IL） is one of the important parameters of asymmetrical digital subscriber loop （ADSL） transformers. In different frequency bands, the factors that affect insertion loss are different. Windings mainly affect insertion loss in mid and high frequency bands. The effects of winding ways, winding wire diameter and winding turns on insertion loss were discussed. The presented experiment shows that the insertion loss of an ADSL transformer could be under 0.4 dB in mid frequency band when the winding is 30 turns, in which the ADSL transformer satisfies the requirement of total harmonic distortion （THD）. Our experiments also show that the sandwich winding structure is better than the side by side winding structure and the twisted-pair winding structure, and the increase of winding diameter is one means to reduce insertion losses of an ADSL transformer in mid frequency band.展开更多
This paper reports a contact cantilever MEMS switch. The designed switch has a metal cantilever that acts as an electrostatically activated switch with processing options to achieve dielectric isolation of the control...This paper reports a contact cantilever MEMS switch. The designed switch has a metal cantilever that acts as an electrostatically activated switch with processing options to achieve dielectric isolation of the controlvoltage path from the signal path. To obtain good material properties,an ANSYS FEA tool is used to optimize the structure. The RF MEMS switch is fabricated via a surface micromachining process. The switch has an actuation voltage of 12V,which is close to the simulated value of 11V. The measured and the HFSS simulated isolations are both higher than - 20dB from 0.05 to 10GHz. The measured insertion loss is less than - 0.9dB, relatively larger than the simulated loss of less than - 0.2dB from 0.05 to 10GHz. This is because a contact resistance introduced due to poor physical contact between the bottom lines and the metal cantilever.展开更多
Vibration and noise aspects play a relevant role in the lifetime and comfort of urban areas and their resi-dents.Among the different sources,the one coming from the rail transit system will play a central concern in t...Vibration and noise aspects play a relevant role in the lifetime and comfort of urban areas and their resi-dents.Among the different sources,the one coming from the rail transit system will play a central concern in the following years due to its sustainability.Ground-borne vibration and noise assessment as well as techniques to mitigate them become key elements of the environmental impact and the global enlargement planned for the railway industry.This paper aims to describe and compare the different mitigation systems existing and reported in liter-ature through a comprehensive state of the art analysis providing the performance of each measure.First,an introduction to the ground-borne vibration and noise gen-erated from the wheel-rail contact and its propagation through the transmission path is presented.Then,the impact and the different ways of evaluating and assessing these effects are presented,and the insertion loss indicator is introduced.Next,the different mitigation measures at different levels(vehicle,track,transmission path and receiver)are discussed by describing their possible appli-cation and their efficiency in terms of insertion loss.Finally,a summary with inputs of how it is possible to address the future of mitigation systems is reported.展开更多
Diesel particulate filter (DPF) is an important factor which influences the sound from exhaust system of an engine. In order to understand the propagation law of sound wave and predict the insertion loss in DPF, based...Diesel particulate filter (DPF) is an important factor which influences the sound from exhaust system of an engine. In order to understand the propagation law of sound wave and predict the insertion loss in DPF, based on the general aero-dynamic equations and Darcy′s law, an acoustic property calculation model of DPF is constructed. Propagation and attenuation characteristics of the forward and backward propagating acoustic waves in the close and open pipe of the filter are investigated. The theoretical model is combined with experiment to investigate sound attenuation property of DPF. The insertion loss obtained from the experiment is compared with that computed for a DPF. The results from the experiment and theoretical calculation agree well.展开更多
基金supported in part by the National Natural Science Foundations of China (Nos.51708422, 51678446,51408434)China Scholarship Council and cole Nationale des Ponts et Chaussées,for providing necessary financial assistance to LI Qiutong to pursue her Ph.D.in France
文摘Many countries which seek to understand the acoustic performance of railway noise barriers have established standards for the conduct of in-situ experiments.However,there are no universally acknowledged receiver positions for the evaluation of the barrier performance,a fact which may be leading to uncertainty over the noise reduction capabilities of available barriers.In terms of the descriptor of the barrier performance,the general recommendation is the A-weighted sound pressure level,although the latter is considered to underestimate low frequencies for railway noise barrier.Thus,in this study,the comparison of receiver positions and the descriptors among existing Chinese,ISO and European standards were investigated.Based upon a combination of diffraction theory and standards,a rearrangement of receiver positions and one-third-octave-band analysis were proposed.In addition,in line with improved methods,an in-situ measurement of insertion loss for a 1.5 mhigh railway noise barrier was designed and conducted.The results of the experiment validate as effective and applicable the new receiver positions.These results also suggest that one-third-octave-band analysis is indispensable.
文摘Fiber Fabry-Perot (FFP) filters have been widely used in optical fiber communications, and insertion loss (IL) is one of its important characteristics. Based on theoretically analysis, factors related to IL were discussed. In order to investigate the IL of different structures, simulations are carried out with finite-difference time-domain (FDTD) algorithm. Comparisons are made between the optimized structure and full-size-mirror FFP filter, and fiber-inserted FFP filter as well. Simulation results demonstrated that the finite- size-mirror structure can confine the mode size of the open resonator, hence reduce the IL of FFP filter.
文摘Insertion loss （IL） is one of the important parameters of asymmetrical digital subscriber loop （ADSL） transformers. In different frequency bands, the factors that affect insertion loss are different. Windings mainly affect insertion loss in mid and high frequency bands. The effects of winding ways, winding wire diameter and winding turns on insertion loss were discussed. The presented experiment shows that the insertion loss of an ADSL transformer could be under 0.4 dB in mid frequency band when the winding is 30 turns, in which the ADSL transformer satisfies the requirement of total harmonic distortion （THD）. Our experiments also show that the sandwich winding structure is better than the side by side winding structure and the twisted-pair winding structure, and the increase of winding diameter is one means to reduce insertion losses of an ADSL transformer in mid frequency band.
文摘This paper reports a contact cantilever MEMS switch. The designed switch has a metal cantilever that acts as an electrostatically activated switch with processing options to achieve dielectric isolation of the controlvoltage path from the signal path. To obtain good material properties,an ANSYS FEA tool is used to optimize the structure. The RF MEMS switch is fabricated via a surface micromachining process. The switch has an actuation voltage of 12V,which is close to the simulated value of 11V. The measured and the HFSS simulated isolations are both higher than - 20dB from 0.05 to 10GHz. The measured insertion loss is less than - 0.9dB, relatively larger than the simulated loss of less than - 0.2dB from 0.05 to 10GHz. This is because a contact resistance introduced due to poor physical contact between the bottom lines and the metal cantilever.
基金financially supported by the European Union’s Horizon 2020 research and innovation programme under the Marie Sk?odowska-Curie grant agreement No INSPIRE813424。
文摘Vibration and noise aspects play a relevant role in the lifetime and comfort of urban areas and their resi-dents.Among the different sources,the one coming from the rail transit system will play a central concern in the following years due to its sustainability.Ground-borne vibration and noise assessment as well as techniques to mitigate them become key elements of the environmental impact and the global enlargement planned for the railway industry.This paper aims to describe and compare the different mitigation systems existing and reported in liter-ature through a comprehensive state of the art analysis providing the performance of each measure.First,an introduction to the ground-borne vibration and noise gen-erated from the wheel-rail contact and its propagation through the transmission path is presented.Then,the impact and the different ways of evaluating and assessing these effects are presented,and the insertion loss indicator is introduced.Next,the different mitigation measures at different levels(vehicle,track,transmission path and receiver)are discussed by describing their possible appli-cation and their efficiency in terms of insertion loss.Finally,a summary with inputs of how it is possible to address the future of mitigation systems is reported.
基金Supported by Natural Science Foundation of Tianjin (05YFJMJC10700).
文摘Diesel particulate filter (DPF) is an important factor which influences the sound from exhaust system of an engine. In order to understand the propagation law of sound wave and predict the insertion loss in DPF, based on the general aero-dynamic equations and Darcy′s law, an acoustic property calculation model of DPF is constructed. Propagation and attenuation characteristics of the forward and backward propagating acoustic waves in the close and open pipe of the filter are investigated. The theoretical model is combined with experiment to investigate sound attenuation property of DPF. The insertion loss obtained from the experiment is compared with that computed for a DPF. The results from the experiment and theoretical calculation agree well.
