In this paper, the solution to the structure consisting of a bead and a board is given as a result of the application of the subregion function method which was suggested in ref. [1]. The same problem is also computed...In this paper, the solution to the structure consisting of a bead and a board is given as a result of the application of the subregion function method which was suggested in ref. [1]. The same problem is also computed with finite element method. The comparison between the two results shows that the application of the subregion function in the method of weighted residuals is practical and effective, especially for solving compound structures.展开更多
在硬件在回路仿真系统中,模型需与数据采集卡之间进行实时数据的采集和交换,Simulink下Real Time Workspace工具箱提供了与硬件之间的实时数据采集和交换,但是工具箱并不支持市面上所有采集板卡的类型,给用户对采集板卡选型带来一定局...在硬件在回路仿真系统中,模型需与数据采集卡之间进行实时数据的采集和交换,Simulink下Real Time Workspace工具箱提供了与硬件之间的实时数据采集和交换,但是工具箱并不支持市面上所有采集板卡的类型,给用户对采集板卡选型带来一定局限性。因此本文使用Simulink中S-Function模块编写不同采集板卡的硬件驱动,证明只要是数据采集工具箱支持的板卡型号,都可以用S-Function进行模块化硬件驱动编写,解决了Simulink中Real Time Workspace工具箱给用户在使用Simulink建模过程中对板卡选型的局限性这一问题。展开更多
列控系统的安全苛求对车载设备的可靠性提出了更高的需求,有效的可靠性模型与合理的维修策略对预防潜在故障、提高设备可靠性具有重要意义。针对现有车载设备可靠性建模和维修策略考虑因素不全面的问题,提出了一种考虑随机冲击与冗余的...列控系统的安全苛求对车载设备的可靠性提出了更高的需求,有效的可靠性模型与合理的维修策略对预防潜在故障、提高设备可靠性具有重要意义。针对现有车载设备可靠性建模和维修策略考虑因素不全面的问题,提出了一种考虑随机冲击与冗余的可靠性模型构建方法与一种不完美维修条件下的预防性维修模型。首先,考虑自然性能退化和外界随机冲击,针对车载设备及其冗余分别建立不同的性能退化模型并计算相应的可靠度函数;其次,利用Copula函数求解联合分布函数作为整体可靠度函数,在可靠度阈值约束下,通过单个预防性维修周期内的可靠度函数求解预防性维修间隔,同时考虑不完美维修对于维修策略的影响,以可靠度阈值和预防性维修次数作为决策准则,构建车载设备全生命周期内的维护费用率模型;最后,以列车自动防护控制单元(Automatic Train Protection Control Unit,ATP-CU)为例进行数值仿真,验证所提模型的有效性。结果表明:提出的基于Copula函数求解车载设备及其冗余的可靠性建模方法相比传统的独立可靠性分析方法能够更好地把握其性能的演化情况;在仿真环境下,当可靠度阈值为0.85、预防性维修次数为7次时,ATP-CU及其冗余全生命周期内的最小维护成本率为21.47元·d-1。展开更多
Acupuncture has been shown to lessen the inflammatory reaction after acute spinal cord injury and reduce secondary injury.However,the mechanism of action remains unclear.In this study,a rat model of spinal cord injury...Acupuncture has been shown to lessen the inflammatory reaction after acute spinal cord injury and reduce secondary injury.However,the mechanism of action remains unclear.In this study,a rat model of spinal cord injury was established by compressing the T8-9 segments using a modified Nystrom method.Twenty-four hours after injury,Zusanli（ST36）,Xuanzhong（GB39）,Futu（ST32）and Sanyinjiao（SP6）were stimulated with electroacupuncture.Rats with spinal cord injury alone were used as controls.At 2,4 and 6 weeks after injury,acetylcholinesterase（ACh E）activity at the site of injury,the number of medium and large neurons in the spinal cord anterior horn,glial cell line-derived neurotrophic factor（GDNF）m RNA expression,and Basso,Beattie and Bresnahan locomotor rating scale scores were greater in the electroacupuncture group compared with the control group.These results demonstrate that electroacupuncture increases ACh E activity,up-regulates GDNF m RNA expression,and promotes the recovery of motor neuron function in the anterior horn after spinal cord injury.展开更多
由于仪器传递函数(Instrument Transfer Function,ITF)能准确反映仪器在空间频率上的响应特征,被广泛应用于仪器规范之中。目前多采用刻有单一台阶特征或不同周期正弦特征的平面测试板对干涉仪的ITF进行检测。针对平面测试板无法完成高...由于仪器传递函数(Instrument Transfer Function,ITF)能准确反映仪器在空间频率上的响应特征,被广泛应用于仪器规范之中。目前多采用刻有单一台阶特征或不同周期正弦特征的平面测试板对干涉仪的ITF进行检测。针对平面测试板无法完成高陡度球面/非球面镜检测时ITF标定的问题,提出了根据球面台阶测试板标定高陡度镜面检测的子孔径拼接ITF的方法。通过超精密车削技术制作了球面台阶测试板,并对其进行拼接检测,根据梯度定位法和旋转矩阵完成检测孔径中台阶的定位及采样,利用傅里叶变换方法实现对台阶实测面形的功率谱密度求解,最后与理想面形功率谱密度做比获得ITF。对口径100 mm、曲率半径100 mm、带有同心圆环台阶结构的球面台阶测试板进行拼接检测以及数据分析,实验结果表明:在1 mm-1的空间频率范围内,各个子孔径对高陡度镜面的检测水平平均可达到82.72%,具有较好的检测精度,随后ITF逐渐衰减,当空间频率在1.5 mm^(-1)左右时,仅能达到40%~60%。展开更多
文摘In this paper, the solution to the structure consisting of a bead and a board is given as a result of the application of the subregion function method which was suggested in ref. [1]. The same problem is also computed with finite element method. The comparison between the two results shows that the application of the subregion function in the method of weighted residuals is practical and effective, especially for solving compound structures.
文摘在硬件在回路仿真系统中,模型需与数据采集卡之间进行实时数据的采集和交换,Simulink下Real Time Workspace工具箱提供了与硬件之间的实时数据采集和交换,但是工具箱并不支持市面上所有采集板卡的类型,给用户对采集板卡选型带来一定局限性。因此本文使用Simulink中S-Function模块编写不同采集板卡的硬件驱动,证明只要是数据采集工具箱支持的板卡型号,都可以用S-Function进行模块化硬件驱动编写,解决了Simulink中Real Time Workspace工具箱给用户在使用Simulink建模过程中对板卡选型的局限性这一问题。
文摘列控系统的安全苛求对车载设备的可靠性提出了更高的需求,有效的可靠性模型与合理的维修策略对预防潜在故障、提高设备可靠性具有重要意义。针对现有车载设备可靠性建模和维修策略考虑因素不全面的问题,提出了一种考虑随机冲击与冗余的可靠性模型构建方法与一种不完美维修条件下的预防性维修模型。首先,考虑自然性能退化和外界随机冲击,针对车载设备及其冗余分别建立不同的性能退化模型并计算相应的可靠度函数;其次,利用Copula函数求解联合分布函数作为整体可靠度函数,在可靠度阈值约束下,通过单个预防性维修周期内的可靠度函数求解预防性维修间隔,同时考虑不完美维修对于维修策略的影响,以可靠度阈值和预防性维修次数作为决策准则,构建车载设备全生命周期内的维护费用率模型;最后,以列车自动防护控制单元(Automatic Train Protection Control Unit,ATP-CU)为例进行数值仿真,验证所提模型的有效性。结果表明:提出的基于Copula函数求解车载设备及其冗余的可靠性建模方法相比传统的独立可靠性分析方法能够更好地把握其性能的演化情况;在仿真环境下,当可靠度阈值为0.85、预防性维修次数为7次时,ATP-CU及其冗余全生命周期内的最小维护成本率为21.47元·d-1。
基金supported by a grant from the Shaanxi Province Scientific and Technological Project in China,No.2014TM4193
文摘Acupuncture has been shown to lessen the inflammatory reaction after acute spinal cord injury and reduce secondary injury.However,the mechanism of action remains unclear.In this study,a rat model of spinal cord injury was established by compressing the T8-9 segments using a modified Nystrom method.Twenty-four hours after injury,Zusanli（ST36）,Xuanzhong（GB39）,Futu（ST32）and Sanyinjiao（SP6）were stimulated with electroacupuncture.Rats with spinal cord injury alone were used as controls.At 2,4 and 6 weeks after injury,acetylcholinesterase（ACh E）activity at the site of injury,the number of medium and large neurons in the spinal cord anterior horn,glial cell line-derived neurotrophic factor（GDNF）m RNA expression,and Basso,Beattie and Bresnahan locomotor rating scale scores were greater in the electroacupuncture group compared with the control group.These results demonstrate that electroacupuncture increases ACh E activity,up-regulates GDNF m RNA expression,and promotes the recovery of motor neuron function in the anterior horn after spinal cord injury.
