Over-speeding is a pivotal factor in fatal traffic crashes globally,necessitating robust speed management strategies to augment road safety.In 2021,the National Highway Traffic Safety Administration reported over 1200...Over-speeding is a pivotal factor in fatal traffic crashes globally,necessitating robust speed management strategies to augment road safety.In 2021,the National Highway Traffic Safety Administration reported over 12000 speed-related fatalities in the United States alone.Previous studies aggregated over-speeding tendencies;however,the extent of over-speeding has a significant implication on the crash outcome.This study delves into the prevalence and magnitude of over-speeding in various scenarios,utilizing data from traffic cameras in Edmonton,Canada,and employing a negative binomial statistical model for analysis.The model elucidates the significance and likelihood of over-speeding tenden-cies by incorporating temporal and built environment variables,i.e.,year,month,number of lanes,dwelling unit types,school-related,and open green space.Study results indicated that the aggregation of the over-speeding data tends to underestimate the influence of var-ious factors.Notably,the estimated impact of the posted speed limit for the disaggregated models is up to over two times that for the aggregated model.Further,the summer months exhibit a roughly 25%uptick in speed limit violations for aggregated models while about a 40%uptick in the speed limit violations for disaggregated approaches.Conversely,a dis-cernible decline in over-speeding tendencies is observed with camera enforcement,show-casing a 25%reduction over four years.Built environment variables presented mixed results,with one-unit dwellings associated with a 12%increase in over-speeding,while proximity to schools indicated a 10%decrease.These pivotal findings provide policymakers and practitioners with valuable insights to formulate targeted interventions and counter-measures to curtail speed limit violations and bolster overall road safety conditions.展开更多
With more and more big wind farms integrating to grid,the faults of doubly fed induction generators(DFIGs)grouping tripped off(GTO)have occurred and bring serious power impacts on the grid.Usually,it was considered th...With more and more big wind farms integrating to grid,the faults of doubly fed induction generators(DFIGs)grouping tripped off(GTO)have occurred and bring serious power impacts on the grid.Usually,it was considered that the fault of DFIGs GTO is only related to the low/high voltage disturbances in the grid and manipulated as an electromagnetic transients.But,we discover that the fault of DFIGs GTO are also related to operating condition of DFIGs and schemes of crowbar protection equipped with DFIGs,and it may be extended to an electromechanical transient in some situations.Based on the investigation of the factors related to DFIGs GTO,such as degree of voltage disturbances,operating conditions of DFIGs and schemes of crowbar protection,three types of DFIGs GTOs are classified and corresponding mechanisms are revealed.The calculation methods to confirm the mechanism are established.The effectiveness of the proposed methods are verified by simulating some cases of DFISs GTO.展开更多
文摘Over-speeding is a pivotal factor in fatal traffic crashes globally,necessitating robust speed management strategies to augment road safety.In 2021,the National Highway Traffic Safety Administration reported over 12000 speed-related fatalities in the United States alone.Previous studies aggregated over-speeding tendencies;however,the extent of over-speeding has a significant implication on the crash outcome.This study delves into the prevalence and magnitude of over-speeding in various scenarios,utilizing data from traffic cameras in Edmonton,Canada,and employing a negative binomial statistical model for analysis.The model elucidates the significance and likelihood of over-speeding tenden-cies by incorporating temporal and built environment variables,i.e.,year,month,number of lanes,dwelling unit types,school-related,and open green space.Study results indicated that the aggregation of the over-speeding data tends to underestimate the influence of var-ious factors.Notably,the estimated impact of the posted speed limit for the disaggregated models is up to over two times that for the aggregated model.Further,the summer months exhibit a roughly 25%uptick in speed limit violations for aggregated models while about a 40%uptick in the speed limit violations for disaggregated approaches.Conversely,a dis-cernible decline in over-speeding tendencies is observed with camera enforcement,show-casing a 25%reduction over four years.Built environment variables presented mixed results,with one-unit dwellings associated with a 12%increase in over-speeding,while proximity to schools indicated a 10%decrease.These pivotal findings provide policymakers and practitioners with valuable insights to formulate targeted interventions and counter-measures to curtail speed limit violations and bolster overall road safety conditions.
基金supported in part by the National Basic Research Program of China(2013CB228201)。
文摘With more and more big wind farms integrating to grid,the faults of doubly fed induction generators(DFIGs)grouping tripped off(GTO)have occurred and bring serious power impacts on the grid.Usually,it was considered that the fault of DFIGs GTO is only related to the low/high voltage disturbances in the grid and manipulated as an electromagnetic transients.But,we discover that the fault of DFIGs GTO are also related to operating condition of DFIGs and schemes of crowbar protection equipped with DFIGs,and it may be extended to an electromechanical transient in some situations.Based on the investigation of the factors related to DFIGs GTO,such as degree of voltage disturbances,operating conditions of DFIGs and schemes of crowbar protection,three types of DFIGs GTOs are classified and corresponding mechanisms are revealed.The calculation methods to confirm the mechanism are established.The effectiveness of the proposed methods are verified by simulating some cases of DFISs GTO.
