Optimized anti-vibratory system for stretched canvas artwork hanging in a museum

To prevent the deterioration of artwork on stretched canvas in a museum, it is often necessary to neutralize the transmission of vibrations from sources such as the wall or the floor. An anti-vibratory system easily optimizes vibrations that are transmitted from the floor because the artwork's motion occurs in vertical translation. Hanging artwork, which receives vibrations from the wall, presents a more complex case because the motion consists of a translation and a rotation. This paper presents a model to determine a cutting frequency above which vibrations transmitted to the artwork are lowered. A procedure to obtain the parameters of this model is also presented. Experiments in a laboratory and in the Louvre Museum validate the predicted cutting frequency given by the model. A downloadable spreadsheet is available to apply this method to specific artwork.     

形态学组合滤波方法在机械振动信号处理中的应用

数学形态学是一种非线性信号处理方法,不同于其他信号处理方法,数学形态学变换完全在时域中进行,无需进行时域和频域的转换,运算简单,速度快。工程现场拾取的振动信号往往含有大量噪声干扰,本文采用开闭和闭开的形态学组合滤波方法对振动信号进行处理。通过仿真信号和实测振动信号的处理结果表明,形态学组合滤波方法不仅能保留信号中的低频成分,具有优良的低通特性,同时处理后的信号具有相位保持的优点,对于脉冲干扰或白噪声均真有良好的抑制作用。     

Whole-body vibration can reduce calciuria induced by high protein intakes and may counteract bone resorption: A preliminary study

Abstract

Excess protein intake can adversely affect the bone via an increase in calcium excretion, while suitable mechanical loading promotes osteogenesis. We therefore investigated whether vibration exposure could alleviate the bone mineral losses associated with a metabolic acidosis. Ten healthy individuals aged 22 – 29 years (median = 25) underwent three 5-day study periods while monitoring their dietary intake. The study consisted of recording the participants' usual dietary intake for 5 consecutive days. Participants were then randomly divided into two groups, one of which received a protein supplement (2 g · kg^?1 body mass · day^?1; n = 5) and the other whole-body low-magnitude (3.5 g), low-frequency (30 Hz) mechanical vibration (WBV) delivered through a specially designed vibrating plate for 10 min each day (n = 5). Finally, for the third treatment period, all participants consumed the protein supplement added to their normal diet and were exposed to WBV exercise for 10 min per day. Daily urine samples were collected throughout the experimental periods to determine the excretion of calcium, phosphate, titratable acid, urea, and C-telopeptide. As expected, when the participants underwent the high protein intake, there was an increase in urinary excretion rates of calcium (P < 0.001), phosphate (P < 0.003), urea (P < 0.001), titratable acid (P < 0.001), and C-telopeptide (P < 0.05) compared with baseline values. However, high protein intake coupled with vibration stimulation resulted in a significant reduction in urinary calcium (P = 0.006), phosphate excretion (P = 0.021), and C-telopeptide (P < 0.05) compared with protein intake alone, but did not affect titratable acid and urea output. The participants showed no effect of WBV exercise alone on urinary excretion of calcium, phosphate, urea, titratable acid, or C-telopeptide. The results indicate that vibration stimulation can moderate the increase in bone resorption and reduction in bone formation caused by a metabolic acidosis.     

浅谈一种简单的减振刀杆

本文通以刀具振动相关理论为基础,采用LMS振动噪声与模态测试分析系统进行振动分析,改造了一根普通刀杆使其成为具有一定抗振性能的减振刀杆,解决了机加车间刀具颤振引起的工件表面质量难以达到精度指标的实际问题。     

工具的横向振动对超声加工精度的影响

根据系统的固有频率振型理论、系统的响应,分析了影响加工精度的因素,提出在设计和加工时应注意的问题和应采取的措施.     

Dynamics analysis of vibration process in Particle Impact Noise Detection

Particle Impact Noise Detection (PIND) test is a reliability screening technique for hermetic device that is prescribed by MIL-PRF-39016E. Some test conditions are specified, although MIL-PRF-39016E did not specify how to obtain these condi- tions. This paper establishes the dynamics model of vibration process based on first order mass-spring system. The corresponding Simulink model is also established to simulate vibration process in optional input excitations. The response equations are derived in sinusoidal excitations and the required electromagnetic force waves are computed in order to obtain a given vibration and shock accelerations. Last, some simulation results are given.     

二杆柔性臂动力学建模与控制

用Lagrange方程对二杆柔性臂进行了动力学建模，并且研究了压电智能结构的柔性机械臂的控制，以二杆柔性臂为例讨论了压电传感器/作动器的位置、数量、尺寸以及控制增益对智能柔性臂振动控制效果的影响，可以实时、有效地控制系统的弹性振动。     

A disc-type magneto-rheologic fluid damper

A disc-type magneto-rheological fluid damper operating in shear mode is proposed in this paper, which is based on the special characteristics of the magneto-rheological (MR) fluid with rapid, reversible and dramatic change in its rheological properties by the application of an external magnetic field. The magnetic field of the disc-type MR fluid damper is analysed by the finite element method; the controllability of the disc-type MR fluid damper on the dynamic behaviour of a rotor system; and the effectiveness of the disc-type MR fluid damper in controlling the vibration of a rotor system, are studied in a flexible rotor system with an over-hung disc. It is shown that the magnetic flux density of the disc-type MR fluid damper in the working areas can significantly change with the applied current in the coil; and that the dynamic behavior of the disc-type MR fluid damper can be varied by the application of an external magnetic field produced by a low voltage electromagnetic coil. The disc-type MR fluid damper can significantly change the dynamic characteristics of a rotor system, provided that the location of the disk-type MR fluid damper is carefully chosen. The disc-type MR fluid damper is a new actuator with good dynamic characteristics for rotating machinery.     

高层建筑风振反应被动控制

本文采用矩阵传递法分析了调频质量阻尼器(TMD)被动控制高层建筑风振反应,导出了结构顶层位移、加速度和基底剪力频域内统计特征公式。最后通过实例的结果说明,经过控制后能显著地降低风振反应。     

用CASSY研究RLC电路的振荡特性

用计算机辅助测量和分析系统ＣＡＳＳＹ研究了ＲＬＣ电路。，该系统能迅速，直观地显示实验结果。