Based on hourly precipitation data in eastern China in the warm season during 1961-2000,spatial distributions of frequency for 20 mm h 1 and 50 mm h 1 precipitation were analyzed,and the criteria of short-duration rai...Based on hourly precipitation data in eastern China in the warm season during 1961-2000,spatial distributions of frequency for 20 mm h 1 and 50 mm h 1 precipitation were analyzed,and the criteria of short-duration rainfall events and severe rainfall events are discussed.Furthermore,the percentile method was used to define local hourly extreme precipitation;based on this,diurnal variations and trends in extreme precipitation were further studied.The results of this study show that,over Yunnan,South China,North China,and Northeast China,the most frequent extreme precipitation events occur most frequently in late afternoon and/or early evening.In the Guizhou Plateau and the Sichuan Basin,the maximum frequency of extreme precipitation events occurs in the late night and/or early morning.And in the western Sichuan Plateau,the maximum frequency occurs in the middle of the night.The frequency of extreme precipitation （based on hourly rainfall measurements） has increased in most parts of eastern China,especially in Northeast China and the middle and lower reaches of the Yangtze River,but precipitation has decreased significantly in North China in the past 50 years.In addition,stations in the Guizhou Plateau and the middle and lower reaches of the Yangtze River exhibit significant increasing trends in hourly precipitation extremes during the nighttime more than during the daytime.展开更多
目的应用成分数据分析方法研究幼儿24 h活动行为(24-hour Movement Behavior)与基本动作技能(Fundamental Movement Skills,FMS)之间的关联,以及各活动行为间等时替代后幼儿FMS的预期变化。方法采用ActiGraph wGT3-BT加速度计测量323名...目的应用成分数据分析方法研究幼儿24 h活动行为(24-hour Movement Behavior)与基本动作技能(Fundamental Movement Skills,FMS)之间的关联,以及各活动行为间等时替代后幼儿FMS的预期变化。方法采用ActiGraph wGT3-BT加速度计测量323名3~6岁幼儿(男童181名,女童142名)的身体活动(Physical Activity,PA)、静态行为(Sedentary Behaviour,SB)数据,采用美国大肌肉动作发展测试第3版工具(Test of Gross Motor Development,TGMD-3)测量FMS,睡眠时间由父母报告,成分数据的描述性统计分析、多元线性模型和等时替代均采用R软件完成。结果①幼儿24 h活动时间分布与动作发展关联紧密,中高强度身体活动(Moderate-to-Vigorous Physical Activity,MVPA)在成分之间分布相对稳定,与低强度身体活动(Light Physical Activity,LPA)转换的可能性更大;②幼儿MVPA对移动技能和总动作技能(Total Motor Skill,Total MS)的影响最大,MVPA等时替代其他行为均具有积极效益,其中替换LPA效果最为明显,其他行为等时替代MVPA预示着更低的动作能力,而且预测具有不对称性。结论虽然MVPA对幼儿动作发展影响最大,但更需要从整体视角平衡24 h活动行为对动作发展的影响;在幼儿园、家庭和社区环境中,强调将幼儿的LPA转换为MVPA,以更好地促进其FMS发展。展开更多
目前,电能表计量数据采集节点设定均为独立方式,数据采集范围受到限制,导致单元耗时延长,因此提出无线通信电能表计量数据采集方法的设计与验证。根据数据采集需求和标准,设定基础电能表计量数据采集指标,采用多阶方式,打破数据采集范...目前,电能表计量数据采集节点设定均为独立方式,数据采集范围受到限制,导致单元耗时延长,因此提出无线通信电能表计量数据采集方法的设计与验证。根据数据采集需求和标准,设定基础电能表计量数据采集指标,采用多阶方式,打破数据采集范围的限制,布设多阶交叉数据采集节点,并以此为基础,构建无线通信电能表数据采集模型,采用射频识别(Radio Frequency Identification,RFID)智能归类实现数据采集处理。测试结果表明,设计的方法对电能表计量数据的采集效果更佳、针对性更强,具有实际应用价值。展开更多
This study investigates relationships between congestion and travel time performance metrics and crashes on road segments. The study focuses on work zone routes in Iowa, utilizing 2021 commercially-available probe veh...This study investigates relationships between congestion and travel time performance metrics and crashes on road segments. The study focuses on work zone routes in Iowa, utilizing 2021 commercially-available probe vehicle data and crash data. Travel time performance metrics were derived from the probe vehicle data, and crash counts were obtained from the crash data. Additional variables included road characteristics (traffic volume, road type, segment length) and a categorical variable for the presence of a work zone. A mixed effect linear regression model was employed to identify relationships between road segment crash counts and the selected performance metrics. This was accomplished for two sets of models that include congestion performance measures at different defining threshold values, along with travel time performance measures. The study results indicate that the congestion indicators, certain travel time performance measures, and traffic counts were statistically significant and positively correlated with crash counts. Indicator variables for rural interstate locations and non-active work zones have a stronger influence on crash count than those for municipal interstate locations and active work zones. These findings can inform decision-makers on work zone safety strategies and crash mitigation planning, especially in high traffic volume areas prone to congestion and queues.展开更多
基金supported by the R & D Special Fund for Public Welfare Industry (meteorology)(GYHY201106018)National Key Program for Developing Basic Sciences (Grant No. 2006CB400503)
文摘Based on hourly precipitation data in eastern China in the warm season during 1961-2000,spatial distributions of frequency for 20 mm h 1 and 50 mm h 1 precipitation were analyzed,and the criteria of short-duration rainfall events and severe rainfall events are discussed.Furthermore,the percentile method was used to define local hourly extreme precipitation;based on this,diurnal variations and trends in extreme precipitation were further studied.The results of this study show that,over Yunnan,South China,North China,and Northeast China,the most frequent extreme precipitation events occur most frequently in late afternoon and/or early evening.In the Guizhou Plateau and the Sichuan Basin,the maximum frequency of extreme precipitation events occurs in the late night and/or early morning.And in the western Sichuan Plateau,the maximum frequency occurs in the middle of the night.The frequency of extreme precipitation （based on hourly rainfall measurements） has increased in most parts of eastern China,especially in Northeast China and the middle and lower reaches of the Yangtze River,but precipitation has decreased significantly in North China in the past 50 years.In addition,stations in the Guizhou Plateau and the middle and lower reaches of the Yangtze River exhibit significant increasing trends in hourly precipitation extremes during the nighttime more than during the daytime.
文摘目的应用成分数据分析方法研究幼儿24 h活动行为(24-hour Movement Behavior)与基本动作技能(Fundamental Movement Skills,FMS)之间的关联,以及各活动行为间等时替代后幼儿FMS的预期变化。方法采用ActiGraph wGT3-BT加速度计测量323名3~6岁幼儿(男童181名,女童142名)的身体活动(Physical Activity,PA)、静态行为(Sedentary Behaviour,SB)数据,采用美国大肌肉动作发展测试第3版工具(Test of Gross Motor Development,TGMD-3)测量FMS,睡眠时间由父母报告,成分数据的描述性统计分析、多元线性模型和等时替代均采用R软件完成。结果①幼儿24 h活动时间分布与动作发展关联紧密,中高强度身体活动(Moderate-to-Vigorous Physical Activity,MVPA)在成分之间分布相对稳定,与低强度身体活动(Light Physical Activity,LPA)转换的可能性更大;②幼儿MVPA对移动技能和总动作技能(Total Motor Skill,Total MS)的影响最大,MVPA等时替代其他行为均具有积极效益,其中替换LPA效果最为明显,其他行为等时替代MVPA预示着更低的动作能力,而且预测具有不对称性。结论虽然MVPA对幼儿动作发展影响最大,但更需要从整体视角平衡24 h活动行为对动作发展的影响;在幼儿园、家庭和社区环境中,强调将幼儿的LPA转换为MVPA,以更好地促进其FMS发展。
文摘目前,电能表计量数据采集节点设定均为独立方式,数据采集范围受到限制,导致单元耗时延长,因此提出无线通信电能表计量数据采集方法的设计与验证。根据数据采集需求和标准,设定基础电能表计量数据采集指标,采用多阶方式,打破数据采集范围的限制,布设多阶交叉数据采集节点,并以此为基础,构建无线通信电能表数据采集模型,采用射频识别(Radio Frequency Identification,RFID)智能归类实现数据采集处理。测试结果表明,设计的方法对电能表计量数据的采集效果更佳、针对性更强,具有实际应用价值。
文摘This study investigates relationships between congestion and travel time performance metrics and crashes on road segments. The study focuses on work zone routes in Iowa, utilizing 2021 commercially-available probe vehicle data and crash data. Travel time performance metrics were derived from the probe vehicle data, and crash counts were obtained from the crash data. Additional variables included road characteristics (traffic volume, road type, segment length) and a categorical variable for the presence of a work zone. A mixed effect linear regression model was employed to identify relationships between road segment crash counts and the selected performance metrics. This was accomplished for two sets of models that include congestion performance measures at different defining threshold values, along with travel time performance measures. The study results indicate that the congestion indicators, certain travel time performance measures, and traffic counts were statistically significant and positively correlated with crash counts. Indicator variables for rural interstate locations and non-active work zones have a stronger influence on crash count than those for municipal interstate locations and active work zones. These findings can inform decision-makers on work zone safety strategies and crash mitigation planning, especially in high traffic volume areas prone to congestion and queues.
