By examining a specific case of compensating for nighttime construction noise in Beijing’s construction projects,we explored how the costs of mitigating construction noise disturbance could be fairly distributed amon...By examining a specific case of compensating for nighttime construction noise in Beijing’s construction projects,we explored how the costs of mitigating construction noise disturbance could be fairly distributed among multiple construction projects near residential areas.In this process,the local government played a crucial coordinating role.According to regulations,construction units must include the costs of preventing and controlling construction noise pollution in the project cost.The construction contract should clearly specify the construction unit’s responsibility for noise pollution prevention and control.After signing the contract,the construction unit should promptly undertake relevant measures to minimize disturbances caused by nighttime construction,aiming to reduce the adverse impacts on the community and ensure the smooth progress of the construction project.展开更多
We propose a passive compensation fiber-optic radio frequency（RF） transfer scheme with a nonsynchronized RF stable source during a round-trip time, which can avoid high-precision phase-locking and efficiently suppre...We propose a passive compensation fiber-optic radio frequency（RF） transfer scheme with a nonsynchronized RF stable source during a round-trip time, which can avoid high-precision phase-locking and efficiently suppress the effect of backscattering only using two wavelengths at the same time. A stable frequency signal is directly reproduced by frequency mixing at the remote site. The proposed scheme is validated by the experiment over a 40 km single mode fiber spool using nonsynchronized common commercial RF sources. The influence of the stability of nonsynchronized RF sources on the frequency transfer is investigated over different length fiber links.展开更多
A novel method to partially compensate sigma-delta shaped noise is proposed. By injecting the compensation current into the passive loop filter during the delay time of the phase frequency detector（PFD）,a maximum re...A novel method to partially compensate sigma-delta shaped noise is proposed. By injecting the compensation current into the passive loop filter during the delay time of the phase frequency detector（PFD）,a maximum reduction of the phase noise by about 16dB can be achieved. Compared to other compensation methods,the technique proposed here is relatively simple and easy to implement. Key building blocks for realizing the noise cancellation,including the delay variable PFD and compensation current source, are specially designed. Both the behavior level and circuit level simulation results are presented.展开更多
Optical transmission technologies have gone through several generations of development.Spectral efficiency has significant ly improved,and industry has begun to search for an answer to a basic question：What are the f...Optical transmission technologies have gone through several generations of development.Spectral efficiency has significant ly improved,and industry has begun to search for an answer to a basic question：What are the fundamental linear and nonlin ear signal channel limitations of the Shannon theory when there is no compensation in an optical fiber transmission system？Next-generation technologies should exceed the 100G transmis sion capability of coherent systems in order to approach the Shannon limit.Spectral efficiency first needs to be improved be fore overall transmission capability can be improved.The means to improve spectral efficiency include more complex modulation formats and channel encoding/decoding algorithms,prefiltering with multisymbol detection,optical OFDM and Ny quist WDM multicarrier technologies,and nonlinearity compen sation.With further optimization,these technologies will most likely be incorporated into beyond-100G optical transport sys tems to meet bandwidth demand.展开更多
文摘By examining a specific case of compensating for nighttime construction noise in Beijing’s construction projects,we explored how the costs of mitigating construction noise disturbance could be fairly distributed among multiple construction projects near residential areas.In this process,the local government played a crucial coordinating role.According to regulations,construction units must include the costs of preventing and controlling construction noise pollution in the project cost.The construction contract should clearly specify the construction unit’s responsibility for noise pollution prevention and control.After signing the contract,the construction unit should promptly undertake relevant measures to minimize disturbances caused by nighttime construction,aiming to reduce the adverse impacts on the community and ensure the smooth progress of the construction project.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.61627817 and 61535006)
文摘We propose a passive compensation fiber-optic radio frequency（RF） transfer scheme with a nonsynchronized RF stable source during a round-trip time, which can avoid high-precision phase-locking and efficiently suppress the effect of backscattering only using two wavelengths at the same time. A stable frequency signal is directly reproduced by frequency mixing at the remote site. The proposed scheme is validated by the experiment over a 40 km single mode fiber spool using nonsynchronized common commercial RF sources. The influence of the stability of nonsynchronized RF sources on the frequency transfer is investigated over different length fiber links.
文摘A novel method to partially compensate sigma-delta shaped noise is proposed. By injecting the compensation current into the passive loop filter during the delay time of the phase frequency detector（PFD）,a maximum reduction of the phase noise by about 16dB can be achieved. Compared to other compensation methods,the technique proposed here is relatively simple and easy to implement. Key building blocks for realizing the noise cancellation,including the delay variable PFD and compensation current source, are specially designed. Both the behavior level and circuit level simulation results are presented.
基金supported by National High-Tech Research and Development Program of China under Grant No.2013AA010501
文摘Optical transmission technologies have gone through several generations of development.Spectral efficiency has significant ly improved,and industry has begun to search for an answer to a basic question：What are the fundamental linear and nonlin ear signal channel limitations of the Shannon theory when there is no compensation in an optical fiber transmission system？Next-generation technologies should exceed the 100G transmis sion capability of coherent systems in order to approach the Shannon limit.Spectral efficiency first needs to be improved be fore overall transmission capability can be improved.The means to improve spectral efficiency include more complex modulation formats and channel encoding/decoding algorithms,prefiltering with multisymbol detection,optical OFDM and Ny quist WDM multicarrier technologies,and nonlinearity compen sation.With further optimization,these technologies will most likely be incorporated into beyond-100G optical transport sys tems to meet bandwidth demand.
