This paper presents quiet zone design using ultrasonic transducers for local active control in pure tone diffuse fields. Most of researches in local active noise control used conventional loudspeakers for the secondar...This paper presents quiet zone design using ultrasonic transducers for local active control in pure tone diffuse fields. Most of researches in local active noise control used conventional loudspeakers for the secondary sources to produce quiet zones. Recently ultrasonic transducers have been used for the secondary sources to control the plane wave in active noise control. However there is no research related to active noise control in diffuse fields using ultrasonic transducers. Therefore this study uses ultrasonic transducers for the secondary sources to control the diffuse fields. The quiet zone produced using ultrasonic transducers in single tone diffuse fields has been analyzed through simulations in this work. The results showed that quiet zones created using ultrasonic transducers were larger than those created using conventional loudspeakers. This is due to the fact that the audible sound pressure produced by the ultrasonic transducers decays slowly with the distance. Therefore the secondary field created by an ultrasonic transducer could fit the primary field better and the larger zone of quiet could be obtained using the ultrasonic transducer. Also the audible sound produced by the ultrasonic transducers is directional;therefore the sound pressure amplification outside the quiet zones was lower.展开更多
Guided by the Planning of Poyang Lake Eco-economic Zone, traffic and geographic conditions of the Eco-agricultural Demonstration Base in the study area were analyzed, and design principles proposed as "adaptation...Guided by the Planning of Poyang Lake Eco-economic Zone, traffic and geographic conditions of the Eco-agricultural Demonstration Base in the study area were analyzed, and design principles proposed as "adaptation to local conditions, scientific planning, benign circulation and sustainable development". Detailed planning and design was interpreted from the perspectives of infrastructure planning and functional area planning. Specifically, infrastructure construction should focus on traffic design, water, power and gas supply design, and also architectural design; while functional areas should be gradually developed from south section to central and then north section. It was to establish a design and planning mode that can be widely applied.展开更多
Numerical simulations and experiments showed that bump inlet had a remarkable effect on boundary layer diversion of supersonic flow.However,the design and analysis of bump in hypersonic flow was still few.In this pape...Numerical simulations and experiments showed that bump inlet had a remarkable effect on boundary layer diversion of supersonic flow.However,the design and analysis of bump in hypersonic flow was still few.In this paper,the mechanism of a supersonic bump inlet is introduced to the design of hypersonic forebody.A hypersonic inlet with an integrated bump/forebody is obtained by the Method Of Characteristics(MOC)based on a chin inlet.Numerical simulations show that the modified inlet achieves diversion of low-speed flow.Besides,the integrated bump/-forebody is also beneficial to inlet start.During the starting process,the shape of the separation zone is rebuilt by the modified forebody surface which makes spillage much easier.This new design leads to a reduction of the self-start Mach number by 0.95.展开更多
The uncertainty and sensitivity of predicted positions and thicknesses of seawater-freshwater mixing zones with respect to uncertainties of saturated hydraulic conductivity, porosity, molecular diffusivity, longitudin...The uncertainty and sensitivity of predicted positions and thicknesses of seawater-freshwater mixing zones with respect to uncertainties of saturated hydraulic conductivity, porosity, molecular diffusivity, longitudinal and transverse dispersivities were investigated in both head-control and flux-control inland boundary systems. It shows that uncertainties and sensitivities of predicted results vary in different boundary systems. With the same designed matrix of uncertain factors in simulation experiments, the variance of predicted positions and thickness in the flux-control system is much larger than that predicted in the head-control system. In a head-control system, the most sensitive factors for the predicted position of the mixing zone are inland freshwater head and transverse dispersivity. However, the predicted position of the mixing zone is more sensitive to saturated hydraulic conductivity in a flux-control system. In a head-control system, the most sensitive factors for the predicted thickness of the mixing zone include transverse dispersivity, molecular diffusivity, porosity, and longitudinal dispersivity, but the predicted thickness is more sensitive to the saturated hydraulic conductivity in a flux-control system. These findings improve our understandings for the development of seawater-freshwater mixing zone during seawater intrusion processes, and give technical support for groundwater resource management in coastal aquifers.展开更多
海岸带是陆地、海洋、大气相互作用的地球生态关键带,汇集了大量的物质和能量,正经历着高强度人类活动、全球气候变化和物种入侵的叠加影响,面临着前所未有的挑战。遥感科学与技术是全面、系统、深入监测海岸带资源、生态、环境的有效...海岸带是陆地、海洋、大气相互作用的地球生态关键带,汇集了大量的物质和能量,正经历着高强度人类活动、全球气候变化和物种入侵的叠加影响,面临着前所未有的挑战。遥感科学与技术是全面、系统、深入监测海岸带资源、生态、环境的有效手段。本文从海岸带独特性和遥感技术优势出发,借助Web of Science和CNKI数据库,分析了海岸带遥感国内外研究现状,探讨了海岸带遥感所面临的科学技术问题,综述了研究进展,明确了机遇与挑战,讨论了未来发展方向。本文可为科学认识海岸带遥感中存在的问题,把握海岸带遥感发展方向提供参考。展开更多
文摘This paper presents quiet zone design using ultrasonic transducers for local active control in pure tone diffuse fields. Most of researches in local active noise control used conventional loudspeakers for the secondary sources to produce quiet zones. Recently ultrasonic transducers have been used for the secondary sources to control the plane wave in active noise control. However there is no research related to active noise control in diffuse fields using ultrasonic transducers. Therefore this study uses ultrasonic transducers for the secondary sources to control the diffuse fields. The quiet zone produced using ultrasonic transducers in single tone diffuse fields has been analyzed through simulations in this work. The results showed that quiet zones created using ultrasonic transducers were larger than those created using conventional loudspeakers. This is due to the fact that the audible sound pressure produced by the ultrasonic transducers decays slowly with the distance. Therefore the secondary field created by an ultrasonic transducer could fit the primary field better and the larger zone of quiet could be obtained using the ultrasonic transducer. Also the audible sound produced by the ultrasonic transducers is directional;therefore the sound pressure amplification outside the quiet zones was lower.
文摘Guided by the Planning of Poyang Lake Eco-economic Zone, traffic and geographic conditions of the Eco-agricultural Demonstration Base in the study area were analyzed, and design principles proposed as "adaptation to local conditions, scientific planning, benign circulation and sustainable development". Detailed planning and design was interpreted from the perspectives of infrastructure planning and functional area planning. Specifically, infrastructure construction should focus on traffic design, water, power and gas supply design, and also architectural design; while functional areas should be gradually developed from south section to central and then north section. It was to establish a design and planning mode that can be widely applied.
文摘Numerical simulations and experiments showed that bump inlet had a remarkable effect on boundary layer diversion of supersonic flow.However,the design and analysis of bump in hypersonic flow was still few.In this paper,the mechanism of a supersonic bump inlet is introduced to the design of hypersonic forebody.A hypersonic inlet with an integrated bump/forebody is obtained by the Method Of Characteristics(MOC)based on a chin inlet.Numerical simulations show that the modified inlet achieves diversion of low-speed flow.Besides,the integrated bump/-forebody is also beneficial to inlet start.During the starting process,the shape of the separation zone is rebuilt by the modified forebody surface which makes spillage much easier.This new design leads to a reduction of the self-start Mach number by 0.95.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51309091,51239003 and 51279045)the Postdoctoral Science Foundation of China(Grant No.2012M520989)
文摘The uncertainty and sensitivity of predicted positions and thicknesses of seawater-freshwater mixing zones with respect to uncertainties of saturated hydraulic conductivity, porosity, molecular diffusivity, longitudinal and transverse dispersivities were investigated in both head-control and flux-control inland boundary systems. It shows that uncertainties and sensitivities of predicted results vary in different boundary systems. With the same designed matrix of uncertain factors in simulation experiments, the variance of predicted positions and thickness in the flux-control system is much larger than that predicted in the head-control system. In a head-control system, the most sensitive factors for the predicted position of the mixing zone are inland freshwater head and transverse dispersivity. However, the predicted position of the mixing zone is more sensitive to saturated hydraulic conductivity in a flux-control system. In a head-control system, the most sensitive factors for the predicted thickness of the mixing zone include transverse dispersivity, molecular diffusivity, porosity, and longitudinal dispersivity, but the predicted thickness is more sensitive to the saturated hydraulic conductivity in a flux-control system. These findings improve our understandings for the development of seawater-freshwater mixing zone during seawater intrusion processes, and give technical support for groundwater resource management in coastal aquifers.
文摘海岸带是陆地、海洋、大气相互作用的地球生态关键带,汇集了大量的物质和能量,正经历着高强度人类活动、全球气候变化和物种入侵的叠加影响,面临着前所未有的挑战。遥感科学与技术是全面、系统、深入监测海岸带资源、生态、环境的有效手段。本文从海岸带独特性和遥感技术优势出发,借助Web of Science和CNKI数据库,分析了海岸带遥感国内外研究现状,探讨了海岸带遥感所面临的科学技术问题,综述了研究进展,明确了机遇与挑战,讨论了未来发展方向。本文可为科学认识海岸带遥感中存在的问题,把握海岸带遥感发展方向提供参考。
