In this paper,the flocking flight of Northern Bald Ibises(Geronticus eremita)and their induced drag during the flock are investigated.Northern Bald Ibises are long-range migratory birds.These birds fly in an echelon a...In this paper,the flocking flight of Northern Bald Ibises(Geronticus eremita)and their induced drag during the flock are investigated.Northern Bald Ibises are long-range migratory birds.These birds fly in an echelon and V-shaped formation,possibly to reduce their drag;therefore,as a result,they may save energy to fly farther.The aerodynamic drag forces of each individual bird and the flock are modeled theoretically.Extensive analysis shows how,during flocking flight,the drag force reduces as the size of the flock increases.Additionally,wingtip spacing effects on the total drag of the flock are investigated.The fraction of drag reduction of individual ibises is also analyzed.Four initial arrangement scenarios are considered for flocks of ibises of different sizes in this study.Two shuffling algorithms are applied for position switching and energy balancing of the ibises during their flight.It is suggested that ibises can save energy by means of different arrangements of flock members during long flights.The results indicate that how different sizes of the birds can manipulate their positions to fly further and save energy during migration.展开更多
Simulating the total ionizing dose(TID)of an electrical system using transistor-level models can be difficult and expensive,particularly for digital-integrated circuits(ICs).In this study,a method for modeling TID eff...Simulating the total ionizing dose(TID)of an electrical system using transistor-level models can be difficult and expensive,particularly for digital-integrated circuits(ICs).In this study,a method for modeling TID effects in complementary metaloxide semiconductor(CMOS)digital ICs based on the input/output buffer information specification(IBIS)was proposed.The digital IC was first divided into three parts based on its internal structure:the input buffer,output buffer,and functional area.Each of these three parts was separately modeled.Using the IBIS model,the transistor V-I characteristic curves of the buffers were processed,and the physical parameters were extracted and modeled using VHDL-AMS.In the functional area,logic functions were modeled in VHDL according to the data sheet.A golden digital IC model was developed by combining the input buffer,output buffer,and functional area models.Furthermore,the golden ratio was reconstructed based on TID experimental data,enabling the assessment of TID effects on the threshold voltage,carrier mobility,and time series of the digital IC.TID experiments were conducted using a CMOS non-inverting multiplexer,NC7SZ157,and the results were compared with the simulation results,which showed that the relative errors were less than 2%at each dose point.This confirms the practicality and accuracy of the proposed modeling method.The TID effect model for digital ICs developed using this modeling technique includes both the logical function of the IC and changes in electrical properties and functional degradation impacted by TID,which has potential applications in the design of radiation-hardening tolerance in digital ICs.展开更多
广东南岭保存着世界上同纬度带上最完整的亚热带植被,森林资源丰富,具有巨大的固碳潜力。然而,目前该地区不同森林植被类型的碳收支年积累量特征及月动态规律尚不明确。选择广东南岭国家级自然保护区内沟谷常绿阔叶林、山地常绿阔叶林...广东南岭保存着世界上同纬度带上最完整的亚热带植被,森林资源丰富,具有巨大的固碳潜力。然而,目前该地区不同森林植被类型的碳收支年积累量特征及月动态规律尚不明确。选择广东南岭国家级自然保护区内沟谷常绿阔叶林、山地常绿阔叶林、针阔叶混交林和山顶常绿阔叶矮林4种典型森林植被为研究对象,运用集成生物圈模型(IBIS)对其2020年总初级生产力(GPP)、净初级生产力(NPP)、净生态系统生产力(NEP)和土壤异养呼吸(Rh)进行模拟,利用样地调查数据对NPP模拟结果进行验证,分析该地区不同植被类型的碳收支年积累量特征及月变化特征。研究结果表明,2020年南岭不同植被类型GPP、NPP、NEP和Rh的平均值分别为1.709、0.718、0.596和0.123 kg C m^(-2)a^(-1),4种植被类型中GPP最高的是沟谷常绿阔叶林,NPP、NEP最高的是山地常绿阔叶林,山顶常绿阔叶矮林的GPP、NPP和NEP均相对较低。南岭不同植被类型全年各月均表现出碳汇(NEP>0),逐月NPP和NEP均表现为双峰变化规律,但不同植被类型的两个峰值所在月份不一致;逐月Rh呈夏季高、冬季低的单峰曲线,夏季时沟谷常绿阔叶林的Rh最高,山顶常绿阔叶矮林的Rh最低。经验证,IBIS模型较好地模拟南岭不同植被类型碳收支情况,模拟值解释了93%的实际碳收支情况,模型对各植被类型的模拟平均相对误差在1.16%-6.07%之间。该研究可为我国亚热带地区南岭森林生态系统的固碳能力评价和森林生态系统资源的管理提供重要参考价值。展开更多
文摘In this paper,the flocking flight of Northern Bald Ibises(Geronticus eremita)and their induced drag during the flock are investigated.Northern Bald Ibises are long-range migratory birds.These birds fly in an echelon and V-shaped formation,possibly to reduce their drag;therefore,as a result,they may save energy to fly farther.The aerodynamic drag forces of each individual bird and the flock are modeled theoretically.Extensive analysis shows how,during flocking flight,the drag force reduces as the size of the flock increases.Additionally,wingtip spacing effects on the total drag of the flock are investigated.The fraction of drag reduction of individual ibises is also analyzed.Four initial arrangement scenarios are considered for flocks of ibises of different sizes in this study.Two shuffling algorithms are applied for position switching and energy balancing of the ibises during their flight.It is suggested that ibises can save energy by means of different arrangements of flock members during long flights.The results indicate that how different sizes of the birds can manipulate their positions to fly further and save energy during migration.
基金This work was supported by the special fund of the State Key Laboratory of Intense Pulsed Radiation Simulation and Effect(No.SKLIPR2011).
文摘Simulating the total ionizing dose(TID)of an electrical system using transistor-level models can be difficult and expensive,particularly for digital-integrated circuits(ICs).In this study,a method for modeling TID effects in complementary metaloxide semiconductor(CMOS)digital ICs based on the input/output buffer information specification(IBIS)was proposed.The digital IC was first divided into three parts based on its internal structure:the input buffer,output buffer,and functional area.Each of these three parts was separately modeled.Using the IBIS model,the transistor V-I characteristic curves of the buffers were processed,and the physical parameters were extracted and modeled using VHDL-AMS.In the functional area,logic functions were modeled in VHDL according to the data sheet.A golden digital IC model was developed by combining the input buffer,output buffer,and functional area models.Furthermore,the golden ratio was reconstructed based on TID experimental data,enabling the assessment of TID effects on the threshold voltage,carrier mobility,and time series of the digital IC.TID experiments were conducted using a CMOS non-inverting multiplexer,NC7SZ157,and the results were compared with the simulation results,which showed that the relative errors were less than 2%at each dose point.This confirms the practicality and accuracy of the proposed modeling method.The TID effect model for digital ICs developed using this modeling technique includes both the logical function of the IC and changes in electrical properties and functional degradation impacted by TID,which has potential applications in the design of radiation-hardening tolerance in digital ICs.
文摘广东南岭保存着世界上同纬度带上最完整的亚热带植被,森林资源丰富,具有巨大的固碳潜力。然而,目前该地区不同森林植被类型的碳收支年积累量特征及月动态规律尚不明确。选择广东南岭国家级自然保护区内沟谷常绿阔叶林、山地常绿阔叶林、针阔叶混交林和山顶常绿阔叶矮林4种典型森林植被为研究对象,运用集成生物圈模型(IBIS)对其2020年总初级生产力(GPP)、净初级生产力(NPP)、净生态系统生产力(NEP)和土壤异养呼吸(Rh)进行模拟,利用样地调查数据对NPP模拟结果进行验证,分析该地区不同植被类型的碳收支年积累量特征及月变化特征。研究结果表明,2020年南岭不同植被类型GPP、NPP、NEP和Rh的平均值分别为1.709、0.718、0.596和0.123 kg C m^(-2)a^(-1),4种植被类型中GPP最高的是沟谷常绿阔叶林,NPP、NEP最高的是山地常绿阔叶林,山顶常绿阔叶矮林的GPP、NPP和NEP均相对较低。南岭不同植被类型全年各月均表现出碳汇(NEP>0),逐月NPP和NEP均表现为双峰变化规律,但不同植被类型的两个峰值所在月份不一致;逐月Rh呈夏季高、冬季低的单峰曲线,夏季时沟谷常绿阔叶林的Rh最高,山顶常绿阔叶矮林的Rh最低。经验证,IBIS模型较好地模拟南岭不同植被类型碳收支情况,模拟值解释了93%的实际碳收支情况,模型对各植被类型的模拟平均相对误差在1.16%-6.07%之间。该研究可为我国亚热带地区南岭森林生态系统的固碳能力评价和森林生态系统资源的管理提供重要参考价值。
