This paper evaluated the significance of the posted differential speed limits(DSL)on traffic safety and operation along interstate highways in South Carolina.This paper defines DSL as the difference between the posted...This paper evaluated the significance of the posted differential speed limits(DSL)on traffic safety and operation along interstate highways in South Carolina.This paper defines DSL as the difference between the posted maximum and minimum speed limits.The paper used vehicle speed and traffic crashes for analysis.The evaluation results showed over 99%of all vehicles complied with the posted 45 mph minimum speed limit and more than 50%of drivers drove above the posted maximum speed limit regardless of the posted maximum speed limits.The results also indicated that speed variations increased as the DSL increased.However,the safety evaluation showed conflicting results on the impacts of the DSL on safety.The results showed the DSL had negative implications on crashes per AADT per lane.This is attributed to increased interactions between slower and faster-moving vehicles in the traffic stream.On the contrary,it was observed that segments with higher DSL had fewer crashes per mile per lane than the segments with the lower DSL.These results suggest there is a need to conduct more research to quantify the efficacy of posting the minimum speed limit because there were no problems observed with motorists driving too slowly on interstate highways.The results provide important information on the efficacy of posting minimum speed limits to improve the uniformity of traffic flow and safety.展开更多
The body channel based wireless power transfer(BC-WPT)method utilizes the human body as the medium to transfer power for bioelectronics,which can achieve a lower transmission loss due to its higher conductivity.Howeve...The body channel based wireless power transfer(BC-WPT)method utilizes the human body as the medium to transfer power for bioelectronics,which can achieve a lower transmission loss due to its higher conductivity.However,except for the channel length,different on-body loca-tions of the transmitter and receiver also influence the power supply performance.This paper fo-cuses on the wrist-to-forehead path to show the potential of BC-WPT for the brain bioelectronics such as the brain computer interface device.The channel characteristics from 10 MHz to 60 MHz are measured by a vector network analyzer(VNA)and a prototype BC-WPT system with differ-ent copper electrodes and the lowest power loss locates between-22 dB and-33 dB.Furthermore,the minimum path loss limit is simulated in Advanced Design System(ADS)software and the low-est optimum path loss can reach nearly-13 dB.Finally,a rectifier circuit is also built at the receiv-er side to harvest d.c.voltage.The results show that the open-circuit voltage(OCV)can reach 1.75 V with the transmitter of 50Ωoutput impedance supplying 5V_(pp)sine voltage at 60 MHz when adopt-ing 1 cm-diameter circular electrodes.展开更多
基金the South Carolina Department of Transportation for providing data that were used in this article and the U.S.Department of Education for the funding support through the HBCU Graduate MST(Grant#P382G170106,2017e2023)。
文摘This paper evaluated the significance of the posted differential speed limits(DSL)on traffic safety and operation along interstate highways in South Carolina.This paper defines DSL as the difference between the posted maximum and minimum speed limits.The paper used vehicle speed and traffic crashes for analysis.The evaluation results showed over 99%of all vehicles complied with the posted 45 mph minimum speed limit and more than 50%of drivers drove above the posted maximum speed limit regardless of the posted maximum speed limits.The results also indicated that speed variations increased as the DSL increased.However,the safety evaluation showed conflicting results on the impacts of the DSL on safety.The results showed the DSL had negative implications on crashes per AADT per lane.This is attributed to increased interactions between slower and faster-moving vehicles in the traffic stream.On the contrary,it was observed that segments with higher DSL had fewer crashes per mile per lane than the segments with the lower DSL.These results suggest there is a need to conduct more research to quantify the efficacy of posting the minimum speed limit because there were no problems observed with motorists driving too slowly on interstate highways.The results provide important information on the efficacy of posting minimum speed limits to improve the uniformity of traffic flow and safety.
文摘The body channel based wireless power transfer(BC-WPT)method utilizes the human body as the medium to transfer power for bioelectronics,which can achieve a lower transmission loss due to its higher conductivity.However,except for the channel length,different on-body loca-tions of the transmitter and receiver also influence the power supply performance.This paper fo-cuses on the wrist-to-forehead path to show the potential of BC-WPT for the brain bioelectronics such as the brain computer interface device.The channel characteristics from 10 MHz to 60 MHz are measured by a vector network analyzer(VNA)and a prototype BC-WPT system with differ-ent copper electrodes and the lowest power loss locates between-22 dB and-33 dB.Furthermore,the minimum path loss limit is simulated in Advanced Design System(ADS)software and the low-est optimum path loss can reach nearly-13 dB.Finally,a rectifier circuit is also built at the receiv-er side to harvest d.c.voltage.The results show that the open-circuit voltage(OCV)can reach 1.75 V with the transmitter of 50Ωoutput impedance supplying 5V_(pp)sine voltage at 60 MHz when adopt-ing 1 cm-diameter circular electrodes.
