Previous studies have reported that, before or after occurrences of strong earthquakes, some low earth orbit satellites recorded ionospheric disturbances, including electromagnetic emissions and plasma fluctuations ov...Previous studies have reported that, before or after occurrences of strong earthquakes, some low earth orbit satellites recorded ionospheric disturbances, including electromagnetic emissions and plasma fluctuations over the epicenter region or its conjugate point.Theoretically speaking, due to some electromagnetic coupling effect, electromagnetic emissions from the earthquake preparation zone could propagate from the lithosphere to the atmosphere, and could reach the ionosphere, even up to the inner magnetosphere. This paper introduces the electric field detector(EFD) onboard the ZhangHeng-1 satellite(ZH-1). The EFD is designed to measure electric field fluctuations within the broad frequency range of DC to 3.5 MHz, divided into 4 channels: ULF(DC–16 Hz), ELF(6 Hz–2.2 kHz), VLF(1.8 kHz–20 kHz) and HF(18 kHz–3.5 MHz). The sampling rates of the channels are 125 Hz, 5 kHz, 50 kHz and 10 MHz, respectively. The EFD includes4 spherical probes mounted on a over 4.5 m boom and an electronic box inside the satellite module. The resolution of the EFD is 1μV·m-1·Hz-1/2 at frequencies from DC to 16 Hz, and the sensitivity is 0.1 μV·m-1·Hz-1/2 at frequencies from 6 Hz to 2.2 kHz, 0.05 μV·m-1·Hz-1/2 in the band 1.8 kHz to 20 kHz, and 0.1μV·m-1·Hz-1/2 from 20 kHz to 3.5 MHz. The dynamic range from DC to 20 kHz is over 120 dB, and over96 dB from 20 kHz to 3.5 MHz. The EFD has two observation modes: survey mode and burst mode. The survey mode concentrates primarily on electric field power density values; the burst mode provides high sampling rate waveform data. The detailed configuration of the EFD onboard the ZH-1 is also introduced in this paper. During the six months' orbit test phase, the EFD recorded a number of natural electromagnetic emissions. Preliminary analysis of these data suggests that the EFD performs well onboard the ZH-1 and is meeting the requirements of the scientific objectives of ZH-1.展开更多
亚洲表面贴装技术和电子制造行业盛会——NEPCON China 2015(NEPCON中国电子展)将于2015年4月21至23日在上海世博展览馆举办,展会涵盖:SMT表面贴装技术、表面焊接技术、电子测量测试、电子制造自动化、防静电等相关技术和产品。全新自...亚洲表面贴装技术和电子制造行业盛会——NEPCON China 2015(NEPCON中国电子展)将于2015年4月21至23日在上海世博展览馆举办,展会涵盖:SMT表面贴装技术、表面焊接技术、电子测量测试、电子制造自动化、防静电等相关技术和产品。全新自动流体点胶系统供应商——诺信EFD届时将在2015NEPCON中国电子展向业内同仁展示其全新P RO系列视觉导引自动点胶解决方案。展开更多
为解决经验傅里叶分解方法(empirical Fourier decomposition,EFD)划分信号频谱边界过于密集且需要预设模态分量数目缺乏自适应性问题,提出基于能量谱线改进经验傅里叶分解(improved empirical Fourier decomposition method based on t...为解决经验傅里叶分解方法(empirical Fourier decomposition,EFD)划分信号频谱边界过于密集且需要预设模态分量数目缺乏自适应性问题,提出基于能量谱线改进经验傅里叶分解(improved empirical Fourier decomposition method based on the energy spectral line,ESL-IEFD)的方法,并用于滚动轴承微弱故障诊断中。首先,计算轴承振动信号快速谱相关图的切片集成能量值,并用滤波平滑性能良好的S-G(Savitzky-Golay)算法进行处理,获得能量谱线;其次,以能量谱线局部最小值位置及频谱两端点作为分割边界,合理划分频谱进而自适应确定模态分量数目;然后,利用构建的零相位滤波器和逆傅里叶变换分别对各频段滤波和重构得到各分量;最后,进行包络谱分析,利用故障特征明显的分量诊断轴承故障。仿真和试验信号分析结果表明:相比EFD和优化EFD,ESL-IEFD方法在频谱频段划分上更合理不再过于密集;在故障诊断效果上,既能有效提取内、外圈单一微弱故障特征,又能对内、外圈复合故障特征进行分离与提取,能够准确诊断轴承故障类型。展开更多
Three-dimensional(3-D)power prediction method from model test has been widely accepted and used for many years.Form factor k is the most important characteristics of 3・D method and very crucial to the accurate power p...Three-dimensional(3-D)power prediction method from model test has been widely accepted and used for many years.Form factor k is the most important characteristics of 3・D method and very crucial to the accurate power prediction.However,it's rather difficult to get the accurate value of k for those ships with pronounced bulbous or large transom from model test.In this paper,a new method to predict power is proposed,using k from CFD while other data from model test(or experimental fluid dynamics(EFD)).Delivered power prediction using the combination of CFD/EFD method agrees well with sea-trial results.展开更多
基金supported by the civil space research project (ZH-1 data validation: Ionospheric observatory theory)NFSC grants 41574139 and 41874174
文摘Previous studies have reported that, before or after occurrences of strong earthquakes, some low earth orbit satellites recorded ionospheric disturbances, including electromagnetic emissions and plasma fluctuations over the epicenter region or its conjugate point.Theoretically speaking, due to some electromagnetic coupling effect, electromagnetic emissions from the earthquake preparation zone could propagate from the lithosphere to the atmosphere, and could reach the ionosphere, even up to the inner magnetosphere. This paper introduces the electric field detector(EFD) onboard the ZhangHeng-1 satellite(ZH-1). The EFD is designed to measure electric field fluctuations within the broad frequency range of DC to 3.5 MHz, divided into 4 channels: ULF(DC–16 Hz), ELF(6 Hz–2.2 kHz), VLF(1.8 kHz–20 kHz) and HF(18 kHz–3.5 MHz). The sampling rates of the channels are 125 Hz, 5 kHz, 50 kHz and 10 MHz, respectively. The EFD includes4 spherical probes mounted on a over 4.5 m boom and an electronic box inside the satellite module. The resolution of the EFD is 1μV·m-1·Hz-1/2 at frequencies from DC to 16 Hz, and the sensitivity is 0.1 μV·m-1·Hz-1/2 at frequencies from 6 Hz to 2.2 kHz, 0.05 μV·m-1·Hz-1/2 in the band 1.8 kHz to 20 kHz, and 0.1μV·m-1·Hz-1/2 from 20 kHz to 3.5 MHz. The dynamic range from DC to 20 kHz is over 120 dB, and over96 dB from 20 kHz to 3.5 MHz. The EFD has two observation modes: survey mode and burst mode. The survey mode concentrates primarily on electric field power density values; the burst mode provides high sampling rate waveform data. The detailed configuration of the EFD onboard the ZH-1 is also introduced in this paper. During the six months' orbit test phase, the EFD recorded a number of natural electromagnetic emissions. Preliminary analysis of these data suggests that the EFD performs well onboard the ZH-1 and is meeting the requirements of the scientific objectives of ZH-1.
文摘亚洲表面贴装技术和电子制造行业盛会——NEPCON China 2015(NEPCON中国电子展)将于2015年4月21至23日在上海世博展览馆举办,展会涵盖:SMT表面贴装技术、表面焊接技术、电子测量测试、电子制造自动化、防静电等相关技术和产品。全新自动流体点胶系统供应商——诺信EFD届时将在2015NEPCON中国电子展向业内同仁展示其全新P RO系列视觉导引自动点胶解决方案。
文摘为解决经验傅里叶分解方法(empirical Fourier decomposition,EFD)划分信号频谱边界过于密集且需要预设模态分量数目缺乏自适应性问题,提出基于能量谱线改进经验傅里叶分解(improved empirical Fourier decomposition method based on the energy spectral line,ESL-IEFD)的方法,并用于滚动轴承微弱故障诊断中。首先,计算轴承振动信号快速谱相关图的切片集成能量值,并用滤波平滑性能良好的S-G(Savitzky-Golay)算法进行处理,获得能量谱线;其次,以能量谱线局部最小值位置及频谱两端点作为分割边界,合理划分频谱进而自适应确定模态分量数目;然后,利用构建的零相位滤波器和逆傅里叶变换分别对各频段滤波和重构得到各分量;最后,进行包络谱分析,利用故障特征明显的分量诊断轴承故障。仿真和试验信号分析结果表明:相比EFD和优化EFD,ESL-IEFD方法在频谱频段划分上更合理不再过于密集;在故障诊断效果上,既能有效提取内、外圈单一微弱故障特征,又能对内、外圈复合故障特征进行分离与提取,能够准确诊断轴承故障类型。
文摘Three-dimensional(3-D)power prediction method from model test has been widely accepted and used for many years.Form factor k is the most important characteristics of 3・D method and very crucial to the accurate power prediction.However,it's rather difficult to get the accurate value of k for those ships with pronounced bulbous or large transom from model test.In this paper,a new method to predict power is proposed,using k from CFD while other data from model test(or experimental fluid dynamics(EFD)).Delivered power prediction using the combination of CFD/EFD method agrees well with sea-trial results.
