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道路平曲线平行线弧长通用公式及应用 被引量:3
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作者 王景海 《城市勘测》 2009年第2期121-124,共4页
由推导不完整回旋曲线平行线弧长公式,得出道路平曲线平行线弧长通用公式。揭示了直线、回旋曲线、圆曲线平行线弧长三者之间的内在联系。得出了一些有益的结论,最后给出了应用回旋曲线平行线弧长计算回旋曲线平行线坐标和推求曲线与平... 由推导不完整回旋曲线平行线弧长公式,得出道路平曲线平行线弧长通用公式。揭示了直线、回旋曲线、圆曲线平行线弧长三者之间的内在联系。得出了一些有益的结论,最后给出了应用回旋曲线平行线弧长计算回旋曲线平行线坐标和推求曲线与平行线间所夹图形面积的具体方法。 展开更多
关键词 道路平曲线平行线 弧长 通用公式 应用
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基于知识与数据驱动的高速路车辆速度计算方法模型研究 被引量:1
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作者 彭大芹 罗裕枫 范兴容 《计算机应用研究》 CSCD 北大核心 2019年第9期2655-2660,共6页
由于目前通过蜂窝基站定位的精度不够高和信令数据产生的不确定性,所以通过手机信令数据估计交通信息参数的精确度仍然是一个巨大的挑战。高速路车辆速度参数是评估道路服务质量最常研究的参数之一,目前基于手机信令数据的交通参数估计... 由于目前通过蜂窝基站定位的精度不够高和信令数据产生的不确定性,所以通过手机信令数据估计交通信息参数的精确度仍然是一个巨大的挑战。高速路车辆速度参数是评估道路服务质量最常研究的参数之一,目前基于手机信令数据的交通参数估计基本步骤为数据收集及预处理、地图匹配、用户路线匹配确定和交通信息参数估计。在此基础上,根据物理运动学知识,针对手机信令数据产生的不确定性和容易参杂平行公路噪声用户数据的影响,提出一种融合距离加权的改进车辆速度计算方法,并在此方法上进一步提出一种消除平行公路干扰数据的车辆速度计算方法,提高计算准确度。利用某移动公司提供的平台进行实例验证,并采用平均绝对误差(MAE)、均方根误差(RMSE)、平均绝对百分比误差(MAPE)作为性能指标,该方法模型性能均优于传统方法模型,并且平均绝对百分比误差比传统方法降低10%左右,具有重要的应用价值。 展开更多
关键词 智能交通系统 手机信令数据 车辆速度 平行道路 噪声数据
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The natural history of flail chest injuries 被引量:2
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作者 Kamil Naidoo Layth Hanbali Peter Bates 《Chinese Journal of Traumatology》 CAS CSCD 2017年第5期293-296,共4页
Purpose: Flail chest (FC) injuries represent a significant burden on trauma services because of its high morbidity and mortality. Current gold standard conservative management strategies for FC, are now being chall... Purpose: Flail chest (FC) injuries represent a significant burden on trauma services because of its high morbidity and mortality. Current gold standard conservative management strategies for FC, are now being challenged by renewed interest in surgical rib fixation. This retrospective epidemiological study sets out to evaluate FC patients, and quantify the natural history of this injury by studying the injury patterns, epidemiology and mortality of patients sustaining FC injuries admitted to a major trauma centre (MTC). Methods: A retrospective cohort analysis has been conducted at an MTC with full trauma service. All patients (age 〉 16 years) sustaining FC were included. Patient demographics, injury characteristics and inpatient stay information were extracted. Results: Two hundred and ninety-three patients were identified, with a mean injury severity score (ISS) of 28.9 (range 9-75), average age of 56.1 years (range of 16-100), and a male predominance (78%). Road traffic accidents accounted for 45% (n = 132) of injuries, whilst 44% were fall or jump from height (n = 129). Associated lung contusion was present in 133 patients (45%) while 76% of patients were found to have 5 or more ribs involved in the flail segment (n = 223) with 96% (n = 281 ) having a unilateral FC. Inpatient treatment was required 19.9 days (range 0-150 days) with 59% of patients (n = 173) requiring intensive care unit (ICU) level care for 8.4 days (range 1-63) with 61.8% requiring mechanical ventilation (n = 107) for 10.5 days (range 1-54), and Z8g underwent rib fixation with rib plates (n = 23). The mortality rate was found to be 14% (n = 42). A non-significant trend towards improved outcomes in the conservative group was found when compared with the fixation group; ventilation days (6.94 vs 10.06, p = 0.18) intensive treatment unit (ITU) length of stay (LOS) (12.56 vs 15.53, p = 0.28) and hospital LOS (32.62 vs 35.24, p = 0.69). Conclusion: This study has successfully described the natural history of flail chest injuries, and has found a nonsignificant trend towards better outcomes with conservative management. With the cohort and management challenges now defined, work on outcome improvement can be targeted. In addition the comnarahility of results to other studies makes collaboration with other MTCs a realistic vrovosal. 展开更多
关键词 Flail chest Natural history Epidemiology Rib plates
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