Wind direction forecasting plays an important role in wind power prediction and air pollution management. Weather quantities such as temperature, precipitation, and wind speed are linear variables in which traditional...Wind direction forecasting plays an important role in wind power prediction and air pollution management. Weather quantities such as temperature, precipitation, and wind speed are linear variables in which traditional model output statistics and bias correction methods are applied. However, wind direction is an angular variable; therefore, such traditional methods are ineffective for its evaluation. This paper proposes an effective bias correction technique for wind direction forecasting of turbine height from numerical weather prediction models, which is based on a circular-circular regression approach. The technique is applied to a 24-h forecast of 65-m wind directions observed at Yangmeishan wind farm, Yunnan Province, China, which consistently yields improvements in forecast performance parameters such as smaller absolute mean error and stronger similarity in wind rose diagram pattern.展开更多
目的 探讨急性缺血性脑卒中(AIS)患者血浆环状RNA(Circ)OGDH、CircHECTD1表达及临床意义。方法 选取2020年12月至2022年12月该院收治的112例AIS患者为AIS组,以同期参加体检的60例健康者为对照组。根据随访出院3个月时AIS患者是否存在血...目的 探讨急性缺血性脑卒中(AIS)患者血浆环状RNA(Circ)OGDH、CircHECTD1表达及临床意义。方法 选取2020年12月至2022年12月该院收治的112例AIS患者为AIS组,以同期参加体检的60例健康者为对照组。根据随访出院3个月时AIS患者是否存在血管性认知功能障碍(VCI)分为VCI组(60例)和非VCI组(52例);根据随访出院3个月时AIS患者的预后情况分为预后良好组(87例)和预后不良组(25例)。采用实时荧光定量PCR检测各组血浆CircOGDH、CircHECTD1表达。采用简易智能精神量表(MMSE)、蒙特利尔认知评估量表(MoCA)及美国国立卫生研究院卒中量表(NIHSS)评分评估AIS患者VCI及神经功能障碍程度。采用Pearson相关分析血浆CircOGDH、CircHECTD1与临床参数的相关性。采用多因素Logistic回归分析影响AIS患者预后不良的因素。采用受试者工作特征(ROC)曲线分析CircOGDH、CircHECTD1单独及联合对AIS患者预后不良的评估价值。结果 AIS组血浆CircOGDH、CircHECTD1相对表达水平高于对照组(t=23.616、29.181,P<0.001)。VCI组血浆CircOGDH、CircHECTD1相对表达水平高于非VCI组(t=12.657、27.667,P<0.001)。相比于预后良好组,预后不良组梗死面积、入院24 h NIHSS评分、CircOGDH、CircHECTD1相对表达水平较高,出院3个月时MMSE评分及MoCA评分较低(均P<0.05)。AIS患者血浆CircOGDH、CircHECTD1与梗死面积、入院24 h NIHSS评分呈正相关,与出院3个月MMSE评分、MoCA评分呈负相关(均P<0.05)。CircOGDH、CircHECTD1相对表达水平升高及梗死面积较大、入院24 h NIHSS评分较高是影响AIS患者预后不良的独立危险因素(均P<0.05)。血浆CircOGDH、CircHECTD1联合预测AIS预后不良的曲线下面积为0.903(95%CI:0.852~0.955),明显大于单一指标的0.831(95%CI:0.781~0.866)和0.836(95%CI:0.794~0.870)(Z=2.258、2.119,P=0.021、0.031)。结论 AIS患者血浆CircOGDH、CircHECTD1表达上调,二者与患者VCI及神经功能障碍程度有关,两项联合对AIS患者预后不良具有较高的预测价值。展开更多
为预估和延长双圆弧谐波减速器刚轮插齿刀有效长度,论文建立了双圆弧刚轮齿廓数学模型,根据运动学法,建立了插刀加工数学仿真模型;根据齿廓法线法,建立了砂轮磨削加工数学模型,推导了刃磨后插刀的等效齿形与加工误差,确定了插刀的有效...为预估和延长双圆弧谐波减速器刚轮插齿刀有效长度,论文建立了双圆弧刚轮齿廓数学模型,根据运动学法,建立了插刀加工数学仿真模型;根据齿廓法线法,建立了砂轮磨削加工数学模型,推导了刃磨后插刀的等效齿形与加工误差,确定了插刀的有效长度。在此基础上,论文通过优化砂轮齿形与插刀齿数,延长了插刀有效长度。结果表明:优化前55齿插刀有效长度为2.1 mm, 0截面插刀加工出刚轮齿形误差为2μm;优化后0截面插刀加工出刚轮齿形误差的最大值为0.14μm。优化后插刀齿数越多,插刀有效长度越长;优化后42齿、55齿、68插刀有效长度分别增加了4.8%、52%、81%。展开更多
基金supported by the Strategic Priority Research Program-Climate Change: Carbon Budget and Related Issues of the Chinese Academy of Sciences (Grant No. XDA05040301)the National Basic Research Program of China (Grant No. 2010CB951804)the National Natural Science Foundation of China (Grant No. 41101045)
文摘Wind direction forecasting plays an important role in wind power prediction and air pollution management. Weather quantities such as temperature, precipitation, and wind speed are linear variables in which traditional model output statistics and bias correction methods are applied. However, wind direction is an angular variable; therefore, such traditional methods are ineffective for its evaluation. This paper proposes an effective bias correction technique for wind direction forecasting of turbine height from numerical weather prediction models, which is based on a circular-circular regression approach. The technique is applied to a 24-h forecast of 65-m wind directions observed at Yangmeishan wind farm, Yunnan Province, China, which consistently yields improvements in forecast performance parameters such as smaller absolute mean error and stronger similarity in wind rose diagram pattern.
文摘目的 探讨急性缺血性脑卒中(AIS)患者血浆环状RNA(Circ)OGDH、CircHECTD1表达及临床意义。方法 选取2020年12月至2022年12月该院收治的112例AIS患者为AIS组,以同期参加体检的60例健康者为对照组。根据随访出院3个月时AIS患者是否存在血管性认知功能障碍(VCI)分为VCI组(60例)和非VCI组(52例);根据随访出院3个月时AIS患者的预后情况分为预后良好组(87例)和预后不良组(25例)。采用实时荧光定量PCR检测各组血浆CircOGDH、CircHECTD1表达。采用简易智能精神量表(MMSE)、蒙特利尔认知评估量表(MoCA)及美国国立卫生研究院卒中量表(NIHSS)评分评估AIS患者VCI及神经功能障碍程度。采用Pearson相关分析血浆CircOGDH、CircHECTD1与临床参数的相关性。采用多因素Logistic回归分析影响AIS患者预后不良的因素。采用受试者工作特征(ROC)曲线分析CircOGDH、CircHECTD1单独及联合对AIS患者预后不良的评估价值。结果 AIS组血浆CircOGDH、CircHECTD1相对表达水平高于对照组(t=23.616、29.181,P<0.001)。VCI组血浆CircOGDH、CircHECTD1相对表达水平高于非VCI组(t=12.657、27.667,P<0.001)。相比于预后良好组,预后不良组梗死面积、入院24 h NIHSS评分、CircOGDH、CircHECTD1相对表达水平较高,出院3个月时MMSE评分及MoCA评分较低(均P<0.05)。AIS患者血浆CircOGDH、CircHECTD1与梗死面积、入院24 h NIHSS评分呈正相关,与出院3个月MMSE评分、MoCA评分呈负相关(均P<0.05)。CircOGDH、CircHECTD1相对表达水平升高及梗死面积较大、入院24 h NIHSS评分较高是影响AIS患者预后不良的独立危险因素(均P<0.05)。血浆CircOGDH、CircHECTD1联合预测AIS预后不良的曲线下面积为0.903(95%CI:0.852~0.955),明显大于单一指标的0.831(95%CI:0.781~0.866)和0.836(95%CI:0.794~0.870)(Z=2.258、2.119,P=0.021、0.031)。结论 AIS患者血浆CircOGDH、CircHECTD1表达上调,二者与患者VCI及神经功能障碍程度有关,两项联合对AIS患者预后不良具有较高的预测价值。
文摘为预估和延长双圆弧谐波减速器刚轮插齿刀有效长度,论文建立了双圆弧刚轮齿廓数学模型,根据运动学法,建立了插刀加工数学仿真模型;根据齿廓法线法,建立了砂轮磨削加工数学模型,推导了刃磨后插刀的等效齿形与加工误差,确定了插刀的有效长度。在此基础上,论文通过优化砂轮齿形与插刀齿数,延长了插刀有效长度。结果表明:优化前55齿插刀有效长度为2.1 mm, 0截面插刀加工出刚轮齿形误差为2μm;优化后0截面插刀加工出刚轮齿形误差的最大值为0.14μm。优化后插刀齿数越多,插刀有效长度越长;优化后42齿、55齿、68插刀有效长度分别增加了4.8%、52%、81%。
