非稳态轧制时轧机振动稳定性的数值分析

利用轧制理论方程和机械振动理论的能量判据 ,给出了一个较精确的分析轧机传动系统扭转振动稳定性的数值计算方法     

液压电梯动态特性与故障诊断试验系统的研制

液压电梯以其独特的优点在电梯市场上显示出的来越强劲的发展势头．液压电梯的动态特性和故障诊断是保证其安全平稳运行所面临的主要研究课题，本文的试验系统就是为此目的面研制的。     

关于VV6102、VV6106风机振动原因分析及整改措施

通过对VV6102、VV6106风机设计资料和现场测试数据，对两台风机的振动原因作出分析，并提出相应整改建议。     

CO2压缩机强烈振动的频谱诊断与治理对策

通过对安庆石化总厂化肥厂ＣＯ＿２压缩机多起强烈振动信号的频谱分析，找出了谱图上的一些规律性特征，并在理论上加以解释，文章还提出了现场应急处理的对策以及根治办法。     

水电站进水塔动水压力研究和探讨

基于理想流体,将进水塔简化成水中悬臂梁体系,推导了其受迫振动时的动力响应方程,给出了进水塔内外表面动水压力的解析表达式。与有限元法、水工抗震规范公式计算结果进行了对比,分析验证了该方法在进水塔结构上的适用性及准确性。结果表明:动水压力表达式与结构振型密切相关。该方法的动水压力曲线趋势与有限元方法相似,均在水面以下某深度处迅速变大及达到最大值后曲线值减小弯回,两者最终在塔体底部收于相近的值;最大值大于有限元法,其最大值处曲线折回明显,幅度较大。弹性模量和进水塔高度对动水压力的曲线形态和数值有重要影响。同时,输入激励荷载的频率对动水压力影响巨大,尤其频率与进水塔某阶频率相近时会导致动水压力的异常增大。该方法对分析进水塔动水压力具有参考价值。     

Response of the seated human body to whole-body vertical vibration: biodynamic responses to sinusoidal and random vibration

The dependence of biodynamic responses of the seated human body on the frequency, magnitude and waveform of vertical vibration has been studied in 20 males and 20 females. With sinusoidal vibration (13 frequencies from 1 to 16 Hz) at five magnitudes (0.1–1.6 ms^? 2 r.m.s.) and with random vibration (1–16 Hz) at the same magnitudes, the apparent mass of the body was similar with random and sinusoidal vibration of the same overall magnitude. With increasing magnitude of vibration, the stiffness and damping of a model fitted to the apparent mass reduced and the resonance frequency decreased (from 6.5 to 4.5 Hz). Male and female subjects had similar apparent mass (after adjusting for subject weight) and a similar principal resonance frequency with both random and sinusoidal vibration. The change in biodynamic response with increasing vibration magnitude depends on the frequency of the vibration excitation, but is similar with sinusoidal and random excitation.     

Response of the seated human body to whole-body vertical vibration: discomfort caused by sinusoidal vibration

Frequency weightings for predicting vibration discomfort assume the same frequency-dependence at all magnitudes of vibration, whereas biodynamic studies show that the frequency-dependence of the human body depends on the magnitude of vibration. This study investigated how the frequency-dependence of vibration discomfort depends on the acceleration and the force at the subject–seat interface. Using magnitude estimation, 20 males and 20 females judged their discomfort caused by sinusoidal vertical acceleration at 13 frequencies (1–16 Hz) at magnitudes from 0.1 to 4.0 ms^? 2 r.m.s. The frequency-dependence of their equivalent comfort contours depended on the magnitude of vibration, but was less dependent on the magnitude of dynamic force than the magnitude of acceleration, consistent with the biodynamic non-linearity of the body causing some of the magnitude-dependence of equivalent comfort contours. There were significant associations between the biodynamic responses and subjective responses at all frequencies in the range 1–16 Hz.

Practitioner Summary: Vertical seat vibration causes discomfort in many forms of transport. This study provides the frequency-dependence of vibration discomfort over a range of vibration magnitudes and shows how the frequency weightings in the current standards can be improved.     

The correlations between structural and optical properties of magnetite nanoparticles synthesised from natural iron sand

The correlations between structural and optical properties of magnetite (Fe₃O₄) nanoparticles were analyzed by using X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) Spectroscopy. The magnetite was synthesised from the iron sand using NaOH, HCl, and NaCl as a solvent. From the quantitative analysis of XRD spectra, the crystallite size (D), strain ($\epsilon$), stress ($\sigma$), energy deformation (u), porosity, and specific surface area were determined. The Kramers Kronig (K–K) relations was applied to the FTIR spectra to determine the optical properties: refractive index (n), extinction coefficient (k), the complex dielectric function ($\mathit{\epsilon }$), and the energy loss function (Im(-1/ε)). The uniform strain was produced from the NaOH and HCl as the solvent. The magnetite had higher porosity with NaCl as a solvent and was directly proportional to the optical phonon vibration. We found a perfect correlation; when the difference between two optical phonon increases, the crystallite size decreases, and the strain will be uniform.     

柔性分离盘抑制圆柱涡激振动的风洞试验

该文利用附属柔性分离盘对圆柱涡激振动(VIV)控制问题进行了风洞试验研究。针对弹性支撑的圆柱及不同长度柔性分离盘的试验模型,在雷诺数7 500-40 000情况下,测定不同约化速度(3.5-18.7)下的振动瞬态位移。结果表明:柔性分离盘长度(L)/圆柱直径(D)比为0.6、0.8和1三种圆柱的横向无因次均方根振幅远小于单圆柱,涡激振动抑制效果很好,均在77.6%以上,其中L=0.8D的圆柱抑制效果最佳,几乎无振动;而L=1.2D和1.5D的圆柱反而出现振动增强,约4.5%和9%。对比单圆柱的共振区,附属柔性分离盘的圆柱共振区在约化速度上更靠后且范围更大。     

基于FPGA的高频全数字低电平系统算法实现

本套加速器高频低电平系统(LLRF)是中国ADS注入器II高频系统的原型机,其工作频率为162.5 MHz,以实现超导加速腔的幅度与相位稳定控制和谐振频率调节。该系统主要由射频前端和数字信号处理FPGA两部分组成。射频前端主要实现高频信号的上下变频和电平匹配;数字信号处理FPGA是系统的核心,主要完成射频信号幅值与相位的数字稳定控制,超导腔谐振频率控制,以及1 000 M以太网通信。在实验室环境下,对该系统进行了幅度和相位稳定度测试,相位稳定度峰峰值为±0.3°,有效值为0.09°,幅值相对稳定度峰峰值为±5×10-3,有效值为3.2×10-3,达到了设计要求。