Let H, K be infinite dimensional complex Hilbert spaces, and A, B be factor von Neumann algebras on H and K, respectively. It is shown that every surjective map completely preserving Jordan 1-＊-zero-product from A to...Let H, K be infinite dimensional complex Hilbert spaces, and A, B be factor von Neumann algebras on H and K, respectively. It is shown that every surjective map completely preserving Jordan 1-＊-zero-product from A to B is a nonzero scalar multiple of either a linear＊-isomorphism or a conjugate linear ＊-isomorphism.展开更多
An organo-montmorillonite-supported nanoscale zero-valent iron material （M-NZVI） was synthesized to degrade decabromodiphenyl ether （BDE-209）. The results showed that nanoscale zero-valent iron had good dispersion...An organo-montmorillonite-supported nanoscale zero-valent iron material （M-NZVI） was synthesized to degrade decabromodiphenyl ether （BDE-209）. The results showed that nanoscale zero-valent iron had good dispersion on organo-montmoriUonite and was present as a core-shell structure with a particle size range of nanoscale iron between 30-90 nm, characterized by XRD, SEM, TEM, XRF, ICP-AES, and XPS. The results of the degradation of BDE-209 by M-NZVI showed that the efficiency of M-NZVI in removing BDE-209 was much higher than that of NZVI. The efficiency of M-NZVI in removing BDE-209 decreased as the pH and the initial dissolved oxygen content of the reaction solution increased, but increased as the proportion of water in the reaction solution increased.展开更多
Understanding crash contributing factors is essential in safety management and improvement. These factors drive investment decisions, policies, regulations, and other safety-related initiatives. This paper analyzes fa...Understanding crash contributing factors is essential in safety management and improvement. These factors drive investment decisions, policies, regulations, and other safety-related initiatives. This paper analyzes factors that contribute to crash occurrence based on two national datasets in the United States (CISS and NASS-CDS) for the years 2017-2022 and 2010-2015, respectively. Three taxonomies were applied to enhance understanding of the various crash contributing factors. These taxonomies were developed based on previous research and practice and involved different groupings of human factors, vehicle factors, and roadway and environmental factors. Statistics for grouping the different types of factors and statistics for specific factors are provided. The results indicate that human factors are present in over 95% of crashes, roadway and environmental factors are present in over 45% of crashes, and vehicle factors are present in less than 2% of crashes. Regarding factors related to human error and vehicle maintenance, speeding is involved in over 25% of crashes, distraction is involved in over 20% of crashes, alcohol and drugs are involved in over 9% of crashes, and vehicle maintenance is involved in approximately 0.45% of crashes. Approximately 4.4% of crashes involve a driver who “looked but did not see.” Weather is involved in over 13% of crashes. Conclusions: The findings indicate that, consistent with previous research, human factors or human error are present in around 95% of crashes. Infrastructure and environmental factors contribute to about 45% of crashes. Vehicle factors contribute to only 1.67% - 1.71% of crashes. The results from this study could potentially be used to inform future safety management and improvement activities, including policy-making, regulation development, safe systems and systemic safety approaches to safety management, and other engineering, education, emergency response, enforcement, evaluation, and encouragement activities. The findings could also be used in the development of future Driver Assistance Technologies (DAT) systems and in enhancing existing technologies.展开更多
为精准估计光伏直流微电网故障电流参数,提升故障电流过零点预测效果,提出一种基于加权最小二乘法(weighted least squares,WLMS)算法的光伏直流微电网故障电流过零点预测方法。通过故障电流参数来估计误差平方加权值与幅度因子,确定WLM...为精准估计光伏直流微电网故障电流参数,提升故障电流过零点预测效果,提出一种基于加权最小二乘法(weighted least squares,WLMS)算法的光伏直流微电网故障电流过零点预测方法。通过故障电流参数来估计误差平方加权值与幅度因子,确定WLMS算法内步长因子的取值范围,改进WLMS算法;利用改进WLMS算法来估计故障电流参数,并依据该结果建立光伏直流微电网故障电流模型;先通过F0假设检验方法在模型内提取故障电流初始相角,再通过调整采样数据窗,令建立的故障电流模型和实际模型相同,则当故障电流初始相角超过设定阈值时,可利用该模型来预测故障电流过零点。实验结果表明:所提方法下,光伏直流微电网故障电流估计的时间常数和初始电压相角与实际结果非常接近,最大误差分别为3 ms和8°;不同故障时,均有效预测了故障电流过零点,准确率为100%;在故障电流内添加谐波后,预测过零点的稳态误差较低,最高稳态误差低于24 A。展开更多
基金Supported by the National Natural Science Foundation of China(Grant No.11501401)
文摘Let H, K be infinite dimensional complex Hilbert spaces, and A, B be factor von Neumann algebras on H and K, respectively. It is shown that every surjective map completely preserving Jordan 1-＊-zero-product from A to B is a nonzero scalar multiple of either a linear＊-isomorphism or a conjugate linear ＊-isomorphism.
基金supported by the National Science and Technology Major Projects of Water Pollution Control andManagement of China (No. 2012ZX07206002)
文摘An organo-montmorillonite-supported nanoscale zero-valent iron material （M-NZVI） was synthesized to degrade decabromodiphenyl ether （BDE-209）. The results showed that nanoscale zero-valent iron had good dispersion on organo-montmoriUonite and was present as a core-shell structure with a particle size range of nanoscale iron between 30-90 nm, characterized by XRD, SEM, TEM, XRF, ICP-AES, and XPS. The results of the degradation of BDE-209 by M-NZVI showed that the efficiency of M-NZVI in removing BDE-209 was much higher than that of NZVI. The efficiency of M-NZVI in removing BDE-209 decreased as the pH and the initial dissolved oxygen content of the reaction solution increased, but increased as the proportion of water in the reaction solution increased.
文摘Understanding crash contributing factors is essential in safety management and improvement. These factors drive investment decisions, policies, regulations, and other safety-related initiatives. This paper analyzes factors that contribute to crash occurrence based on two national datasets in the United States (CISS and NASS-CDS) for the years 2017-2022 and 2010-2015, respectively. Three taxonomies were applied to enhance understanding of the various crash contributing factors. These taxonomies were developed based on previous research and practice and involved different groupings of human factors, vehicle factors, and roadway and environmental factors. Statistics for grouping the different types of factors and statistics for specific factors are provided. The results indicate that human factors are present in over 95% of crashes, roadway and environmental factors are present in over 45% of crashes, and vehicle factors are present in less than 2% of crashes. Regarding factors related to human error and vehicle maintenance, speeding is involved in over 25% of crashes, distraction is involved in over 20% of crashes, alcohol and drugs are involved in over 9% of crashes, and vehicle maintenance is involved in approximately 0.45% of crashes. Approximately 4.4% of crashes involve a driver who “looked but did not see.” Weather is involved in over 13% of crashes. Conclusions: The findings indicate that, consistent with previous research, human factors or human error are present in around 95% of crashes. Infrastructure and environmental factors contribute to about 45% of crashes. Vehicle factors contribute to only 1.67% - 1.71% of crashes. The results from this study could potentially be used to inform future safety management and improvement activities, including policy-making, regulation development, safe systems and systemic safety approaches to safety management, and other engineering, education, emergency response, enforcement, evaluation, and encouragement activities. The findings could also be used in the development of future Driver Assistance Technologies (DAT) systems and in enhancing existing technologies.
文摘目的 :分析颈前路减压Zero-P融合固定术后吞咽困难的影响因素。方法 :对2011年1月~2016年12月行颈前路减压Zero-P融合固定术且至少1年以上的115例患者的资料进行回顾性分析。其中男66例,女49例。采用电话或门诊随访的方式,以Bazaz评分系统评估术后3d吞咽困难程度,根据是否存在术后吞咽困难将所有患者分为吞咽困难组(轻、中、重度吞咽困难患者)和无吞咽困难组,分析性别、年龄、身体质量指数(body mass index,BMI)、糖尿病、高血压、吸烟、饮酒、手术时间、术中出血量、术后椎前软组织肿胀程度(术后软组织厚度与术前软组织厚度的差值)、术后O-C2角度、术后C2-7角度、手术最高节段、手术节段数等因素与术后吞咽困难发生的相关性,并重点探讨术后C2-7角度这一因素。两组间定量变量的差异采用独立样本t检验的方法进行比较,定性变量差异进行卡方检验。为排除混杂因素影响,将单因素分析中P<0.2的因素纳入二元Logistic回归模型进行多因素汇总分析。采用Spearman秩相关检验验证术后C2-7角度与吞咽困难严重程度的相关性。结果:吞咽困难组18例,男11例,女7例;无吞咽困难组97例,男55例,女42例。单因素分析结果显示,年龄、术后O-C2角度、术后C2-7角度及椎前软组织肿胀程度两组间比较均有统计学差异(P<0.05),性别、BMI、糖尿病、高血压、吸烟、饮酒、手术时间、术中出血量、手术最高节段、手术节段数两组间比较均无统计学差异(P>0.05)。单因素分析中P<0.2的因素包括年龄、BMI、术中出血量、术后O-C2角度、术后C2-7角度及术后椎前软组织肿胀。将单因素分析中P<0.2的因素纳入Logistic回归分析,术后C2-7角度及椎前软组织肿胀与术后发生吞咽困难呈显著相关(P<0.05),年龄、BMI、术中出血量和术后O-C2角度与术后吞咽困难的发生均无显著相关性(P>0.05)。吞咽困难组术后C2-7角度为9.17°~36.39°(19.14°±6.73°),无吞咽困难组为1.59°~20.45°(10.88°±5.36°),吞咽困难组术后C2-7角显著大于无吞咽困难组(P<0.05)。将C2-7角≥12°时的吞咽困难发生率(26.2%,16/61)和C2-7角<12°时吞咽困难的发生率(3.7%,2/54)进行比较,差异有统计学意义(P<0.05)。将18例吞咽困难患者(轻度16例,重度2例)的术后C2-7角度与吞咽困难等级进行Spearman秩相关分析,结果显示两者不存在显著相关性(P>0.05)。结论:颈前路减压Zero-P融合固定术后C2-7角度及椎前软组织肿胀对患者术后吞咽困难的发生有重要的影响,术中注意C2-7角度的调整及控制术后的椎前软组织肿胀可降低患者术后发生吞咽困难的风险。
文摘为精准估计光伏直流微电网故障电流参数,提升故障电流过零点预测效果,提出一种基于加权最小二乘法(weighted least squares,WLMS)算法的光伏直流微电网故障电流过零点预测方法。通过故障电流参数来估计误差平方加权值与幅度因子,确定WLMS算法内步长因子的取值范围,改进WLMS算法;利用改进WLMS算法来估计故障电流参数,并依据该结果建立光伏直流微电网故障电流模型;先通过F0假设检验方法在模型内提取故障电流初始相角,再通过调整采样数据窗,令建立的故障电流模型和实际模型相同,则当故障电流初始相角超过设定阈值时,可利用该模型来预测故障电流过零点。实验结果表明:所提方法下,光伏直流微电网故障电流估计的时间常数和初始电压相角与实际结果非常接近,最大误差分别为3 ms和8°;不同故障时,均有效预测了故障电流过零点,准确率为100%;在故障电流内添加谐波后,预测过零点的稳态误差较低,最高稳态误差低于24 A。
