Recent advances in intelligent transportation system allow traffic safety studies to extend from historic data-based analyses to real-time applications. The study presents a new method to predict crash likelihood with...Recent advances in intelligent transportation system allow traffic safety studies to extend from historic data-based analyses to real-time applications. The study presents a new method to predict crash likelihood with traffic data collected by discrete loop detectors as well as the web-crawl weather data. Matched case-control method and support vector machines （SVMs） technique were employed to identify the risk status. The adaptive synthetic over-sampling technique was applied to solve the imbalanced dataset issues. Random forest technique was applied to select the contributing factors and avoid the over-fitting issues. The results indicate that the SVMs classifier could successfully classify 76.32% of the crashes on the test dataset and 87.52% of the crashes on the overall dataset, which were relatively satisfactory compared with the results of the previous studies. Compared with the SVMs classifier without the data, the SVMs classifier with the web-crawl weather data increased the crash prediction accuracy by 1.32% and decreased the false alarm rate by 1.72%, showing the potential value of the massive web weather data. Mean impact value method was employed to evaluate the variable effects, and the results are identical with the results of most of previous studies. The emerging technique based on the discrete traffic data and web weather data proves to be more applicable on real- time safety management on freeways.展开更多
目的探讨实时三平面超声心动图(RT-3PE)测量离体猪心室壁瘤心模型的左室容积,分析此方法的可行性与准确性。方法应用10%福尔马林液固定17个模拟室壁瘤形成的离体猪心,将其浸入水槽中,用二维超声心动图的双平面Simpson法RT-3PE测量左室容...目的探讨实时三平面超声心动图(RT-3PE)测量离体猪心室壁瘤心模型的左室容积,分析此方法的可行性与准确性。方法应用10%福尔马林液固定17个模拟室壁瘤形成的离体猪心,将其浸入水槽中,用二维超声心动图的双平面Simpson法RT-3PE测量左室容积,其值分别与左室注水的真实容积进行对比研究。结果线性回归分析表明实时三平面成像所测左室容积与其真实容积相关性较好(r=0.92,P<0.01);方差分析表明两者间差异无统计学意义(P>0.05)。二维超声心动图双平面Simpson法所测左室容积与真实容积亦具有良好的相关性(r=0.82,P<0.01),但两者间有显著性差异(P<0.05)。Altman and Bland一致性分析显示RT-3PE所测容积与实测容积之间的一致性明显高于二维超声心动图。结论RT-3PE是一快速、准确测量左室室壁瘤左室容积的新方法。展开更多
基金supported by the National Natural Science Foundation (71301119)the Shanghai Natural Science Foundation (12ZR1434100)
文摘Recent advances in intelligent transportation system allow traffic safety studies to extend from historic data-based analyses to real-time applications. The study presents a new method to predict crash likelihood with traffic data collected by discrete loop detectors as well as the web-crawl weather data. Matched case-control method and support vector machines （SVMs） technique were employed to identify the risk status. The adaptive synthetic over-sampling technique was applied to solve the imbalanced dataset issues. Random forest technique was applied to select the contributing factors and avoid the over-fitting issues. The results indicate that the SVMs classifier could successfully classify 76.32% of the crashes on the test dataset and 87.52% of the crashes on the overall dataset, which were relatively satisfactory compared with the results of the previous studies. Compared with the SVMs classifier without the data, the SVMs classifier with the web-crawl weather data increased the crash prediction accuracy by 1.32% and decreased the false alarm rate by 1.72%, showing the potential value of the massive web weather data. Mean impact value method was employed to evaluate the variable effects, and the results are identical with the results of most of previous studies. The emerging technique based on the discrete traffic data and web weather data proves to be more applicable on real- time safety management on freeways.
文摘目的探讨实时三平面超声心动图(RT-3PE)测量离体猪心室壁瘤心模型的左室容积,分析此方法的可行性与准确性。方法应用10%福尔马林液固定17个模拟室壁瘤形成的离体猪心,将其浸入水槽中,用二维超声心动图的双平面Simpson法RT-3PE测量左室容积,其值分别与左室注水的真实容积进行对比研究。结果线性回归分析表明实时三平面成像所测左室容积与其真实容积相关性较好(r=0.92,P<0.01);方差分析表明两者间差异无统计学意义(P>0.05)。二维超声心动图双平面Simpson法所测左室容积与真实容积亦具有良好的相关性(r=0.82,P<0.01),但两者间有显著性差异(P<0.05)。Altman and Bland一致性分析显示RT-3PE所测容积与实测容积之间的一致性明显高于二维超声心动图。结论RT-3PE是一快速、准确测量左室室壁瘤左室容积的新方法。
