This paper aims to reviewthe state-of-the-art of ultrasonic vibration assisted friction stir welding(UVAFSW) process. Particular attention has been paid on the modes of ultrasonic exertion,experimental results and eff...This paper aims to reviewthe state-of-the-art of ultrasonic vibration assisted friction stir welding(UVAFSW) process. Particular attention has been paid on the modes of ultrasonic exertion,experimental results and effects of ultrasonic vibrations on process effectiveness and joint quality. The trends of various aspects with and without ultrasonic vibrations in FSW process are studied and presented. The influence of ultrasonic vibrations on welding loads, temperature history, weld morphology, material flow, weld microstructure and mechanical properties are revisited. Ultrasonic assisted FSW offers numerous advantages over the conventional FSW process. The superimposing of high-frequency vibrations improves various phenomena of the process and the physical,metallurgical,mechanical and tribological properties of the welded joint. The ultrasonic assisted FSW process has a potential to benefit the industry sector. A checklist listing the materials and process parameters used in the documented studies has been presented for quick reference.展开更多
Objective To assess the effects of high-frequency loading using whole body vibration on distal radius density in adults. Methods The volunteers diagnosed with osteoporosis or osteopenia in the First Hospital of Jilin ...Objective To assess the effects of high-frequency loading using whole body vibration on distal radius density in adults. Methods The volunteers diagnosed with osteoporosis or osteopenia in the First Hospital of Jilin University from January 2011 to December 2014 were recruited. All the subjects performed foot-based, whole body vibrations on the vibration platform(35 Hz, 0.25 g) once a day, for 15 minutes per session over a period of 4 weeks. The bone mineral density of distal radius(rB MD) was measured using dual-energy X-ray absorptiometry at before, 2-week, and 4-week after the vibration treatment. Blood pressures were measured at the end of the vibration treatment. Results A total of 114 volunteers were enrolled. The average rB MD before the treatment was 0.331±0.014 g/cm^2. It was reached 0.337±0.019 g/cm2 at the end of the fourth week, increased by 1.79%(P<0.05). Whole body vibration increased rB MD of men and women respectively(1.77% and 1.80%, P<0.05). Blood pressures did not change in any of the groups. Conclusion A 4-week whole body vibration was feasible and contributed to increase of rBMD.展开更多
为进一步提高有载分接开关(on-load tap changer,OLTC)机械状态监测的准确性,文中基于优化品质因数可调小波变换(tunable quality wavelet transform,TQWT)对OLTC切换过程中的振动信号进行了分析。即使用人工鱼群算法(artificial fish s...为进一步提高有载分接开关(on-load tap changer,OLTC)机械状态监测的准确性,文中基于优化品质因数可调小波变换(tunable quality wavelet transform,TQWT)对OLTC切换过程中的振动信号进行了分析。即使用人工鱼群算法(artificial fish swarm algorithm,AFSA)基于分解余量与整体正交系数研究了TQWT的优化分解方法,计算得到了OLTC振动信号的多个子序列,构建了基于优化孪生支持向量机(twin support vector machine,TWSVM)的OLTC机械故障诊断模型。对某CM型OLTC正常与典型机械故障下振动信号的分析结果表明,所提优化TQWT分解方法有效提高了OLTC振动信号分解结果的准确性。相对于其他诊断模型,所构建AFSA-TWSVM的OLTC机械故障诊断模型分类效果好且收敛速度更快。展开更多
In this paper, using the theory of stochastic analysis of the response to earthquake load, a stochastic analysis method of the response of piled platforms to earthquake load has been established. In the method, the st...In this paper, using the theory of stochastic analysis of the response to earthquake load, a stochastic analysis method of the response of piled platforms to earthquake load has been established. In the method, the strong ground motion is considered as three dimensional stationary white noise process and the pile-soil interaction and water-structure interaction are considered. The stochastic response of a typical platform to earthquake load has been computed with this method and the results compared with those obtained with the response spectrum analysis method. The comparison shows that the stochastic analysis method of the response of piled platforms to earthquake load is suitable for this kind of analysis.展开更多
由于有载分接开关(on-load tap changer,OLTC)需要频繁切换和具有严格的运行条件,OLTC已成为电力变压器中最脆弱的部分之一,OLTC故障的准确诊断对保障电力系统稳定运行意义重大。基于变分模态分解将OLTC振动信号分解为数个模态分量,基...由于有载分接开关(on-load tap changer,OLTC)需要频繁切换和具有严格的运行条件,OLTC已成为电力变压器中最脆弱的部分之一,OLTC故障的准确诊断对保障电力系统稳定运行意义重大。基于变分模态分解将OLTC振动信号分解为数个模态分量,基于模态分量提取OLTC振动信号的时域特征参数,并利用一系列故障模拟对OLTC振动信号时域特征参数进行统计性分析。通过这些时域特征参数建立OLTC振动信号数据库,从而实现OLTC故障的诊断。展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant Nos.51475272 and 51550110501)the GKP Acknow ledges the Research Fellow ship of Shandong University
文摘This paper aims to reviewthe state-of-the-art of ultrasonic vibration assisted friction stir welding(UVAFSW) process. Particular attention has been paid on the modes of ultrasonic exertion,experimental results and effects of ultrasonic vibrations on process effectiveness and joint quality. The trends of various aspects with and without ultrasonic vibrations in FSW process are studied and presented. The influence of ultrasonic vibrations on welding loads, temperature history, weld morphology, material flow, weld microstructure and mechanical properties are revisited. Ultrasonic assisted FSW offers numerous advantages over the conventional FSW process. The superimposing of high-frequency vibrations improves various phenomena of the process and the physical,metallurgical,mechanical and tribological properties of the welded joint. The ultrasonic assisted FSW process has a potential to benefit the industry sector. A checklist listing the materials and process parameters used in the documented studies has been presented for quick reference.
基金Supported by the National Natural Science Foundation of China(11272134 and 11432016)
文摘Objective To assess the effects of high-frequency loading using whole body vibration on distal radius density in adults. Methods The volunteers diagnosed with osteoporosis or osteopenia in the First Hospital of Jilin University from January 2011 to December 2014 were recruited. All the subjects performed foot-based, whole body vibrations on the vibration platform(35 Hz, 0.25 g) once a day, for 15 minutes per session over a period of 4 weeks. The bone mineral density of distal radius(rB MD) was measured using dual-energy X-ray absorptiometry at before, 2-week, and 4-week after the vibration treatment. Blood pressures were measured at the end of the vibration treatment. Results A total of 114 volunteers were enrolled. The average rB MD before the treatment was 0.331±0.014 g/cm^2. It was reached 0.337±0.019 g/cm2 at the end of the fourth week, increased by 1.79%(P<0.05). Whole body vibration increased rB MD of men and women respectively(1.77% and 1.80%, P<0.05). Blood pressures did not change in any of the groups. Conclusion A 4-week whole body vibration was feasible and contributed to increase of rBMD.
文摘为进一步提高有载分接开关(on-load tap changer,OLTC)机械状态监测的准确性,文中基于优化品质因数可调小波变换(tunable quality wavelet transform,TQWT)对OLTC切换过程中的振动信号进行了分析。即使用人工鱼群算法(artificial fish swarm algorithm,AFSA)基于分解余量与整体正交系数研究了TQWT的优化分解方法,计算得到了OLTC振动信号的多个子序列,构建了基于优化孪生支持向量机(twin support vector machine,TWSVM)的OLTC机械故障诊断模型。对某CM型OLTC正常与典型机械故障下振动信号的分析结果表明,所提优化TQWT分解方法有效提高了OLTC振动信号分解结果的准确性。相对于其他诊断模型,所构建AFSA-TWSVM的OLTC机械故障诊断模型分类效果好且收敛速度更快。
文摘In this paper, using the theory of stochastic analysis of the response to earthquake load, a stochastic analysis method of the response of piled platforms to earthquake load has been established. In the method, the strong ground motion is considered as three dimensional stationary white noise process and the pile-soil interaction and water-structure interaction are considered. The stochastic response of a typical platform to earthquake load has been computed with this method and the results compared with those obtained with the response spectrum analysis method. The comparison shows that the stochastic analysis method of the response of piled platforms to earthquake load is suitable for this kind of analysis.
文摘由于有载分接开关(on-load tap changer,OLTC)需要频繁切换和具有严格的运行条件,OLTC已成为电力变压器中最脆弱的部分之一,OLTC故障的准确诊断对保障电力系统稳定运行意义重大。基于变分模态分解将OLTC振动信号分解为数个模态分量,基于模态分量提取OLTC振动信号的时域特征参数,并利用一系列故障模拟对OLTC振动信号时域特征参数进行统计性分析。通过这些时域特征参数建立OLTC振动信号数据库,从而实现OLTC故障的诊断。
