Vibration Frequency in Micro-Vibration Therapy in Nursing Care: A Cross-Sectional Study

This study investigated the vibration frequency in micro-vibration therapy (MVT) performed as a part of nursing care in Japan. We surveyed 31 nurses (25 women and 6 men) who performed MVT with accelerometers attached to the backs of their hands, and the data obtained were analyzed. The mean vibration frequency was 8.3 Hz (standard deviation [SD]: 1.9 Hz) bilaterally, with a left-right difference of 0.8 Hz (SD: 1.1 Hz, right > left). Furthermore, vibration frequency was correlated with duration of MVT use (rs = 0.5, P < 0.01). The vibration frequency was higher in men (9.2 Hz, SD: 2.4 Hz) than in women (8.1 Hz, SD: 1.8 Hz), but this difference was not significant (P = 0.34). The vibrations of MVT are of a lower frequency than those of other vibration therapies.

Magneto-rheological elastomer (MRE) based composite structures for micro-vibration control

Magneto-rheological elastomers （MILEs） are used to construct composite structures for micro-vibration control of equipment under stochastic support-motion excitations. The dynamic behavior of MREs as a smart viscoelastic material is characterized by a complex modulus dependent on vibration frequency and controllable by external magnetic fields. Frequency-domain solution methods for stochastic micro-vibration response analysis of the MRE-based structural systems are developed to derive the system frequency-response function matrices and the expressions of the velocity response spectrum. With these equations, the root-mean-square （RMS） velocity responses in terms of the one-third octave frequency band spectrum can be calculated. Further, the optimization problem of the complex moduli of the MRE cores is defined by minimizing the velocity response spectra and the RMS velocity responses through altering the applied magnetic fields. Simulation results illustrate the influences of MRE parameters on the RMS velocity responses and the high response reduction capacities of the MRE-based structures. In addition, the developed frequency-domain analysis methods are applicable to sandwich beam structures with arbitrary cores characterized by complex shear moduli under stochastic excitations described by power spectral density functions, and are valid for a wide frequency range.

Characteristic Analysis and Harmonic Feature Identification of Micro-Vibration on Flywheels

To avoid the negative effects of disturbances on satellites,the characteristics of micro-vibration on flywheels are studied.Considering rotor imbalance,bearing imperfections and structural elasticity,the extended model of micro-vibration is established.In the feature extraction of micro-vibration,singular value decomposition combined with the improved Akaike Information Criterion(AIC-SVD)is applied to denoise.More robust and self-adaptable than the peak threshold denoising,AIC-SVD can effectively remove the noise components.Subsequently,the effective harmonic coefficients are extracted by the binning algorithm.The results show that the harmonic coefficients have great identification in frequency domain.Except for the fundamental frequency caused by rotor imbalance,the harmonics are also caused by the coupling of imperfections on bearing components.

Image motion and experimental study of a 0.1″space pointing measuring instrument for micro-vibration conditions

There exists an increasing need for Milli-Arc-Seconds(MAS)accuracy pointing measurement for current and future space systems.To meet the 0.1″space pointing measurement accuracy requirements of spacecraft in future,the influence of spacecraft micro-vibration on a 0.1″Space Pointing Measuring Instrument(SPMI)is studied.A Quasi-Zero Stiffness Device(QZSD)with adaptive adjustment and variable stroke was proposed.Then,a series of micro-vibration experiments of the SPMI were carried out.The influence of the micro-vibration generated by Guidance Navigation Control(GNC)attitude control components under different attitudes on the SPMI was analyzed.Point spread function of image motion in micro-vibration was also derived.Further,the changes of image motion under the micro-vibration environment were evaluated by extracting the gray centroid of the images,and the experiment processes and results are deeply discussed.The results show that the firstorder frequency of the QZSD system is 0.114 Hz,and it is induced by a double pendulum system;the image motion of single flywheel spinning reached 0.015 pixels;whilst the image motion reached 0.03 pixels when three flywheels are combined spinning.These latest findings provide a beneficial theoretical and technical support for the development of spacecraft with 0·1″pointing accuracy.

Design and experiments of an active isolator for satellite micro-vibration

In this paper, a soft active isolator（SAI） derived from a voice coil motor is studied to determine its abilities as a micro-vibration isolation device for sensitive satellite payloads. Firstly,the two most important parts of the SAI, the mechanical unit and the low-noise driver, are designed and manufactured. Then, a rigid-flexible coupling dynamic model of the SAI is built, and a dynamic analysis is conducted. Furthermore, a controller with a sky-hook damper is designed. Finally,results from the performance tests of the mechanical/electronic parts and the isolation experiments are presented. The SAI attenuations are found to be more than 20 d B above 5 Hz, and the control effect is stable.

Research on separation and enhancement of speech micro-vibration from macro motion

Based on the 1 550 nm all-fiber pulsed laser Doppler vibrometer(LDV) system independently developed by our laboratory, empirical mode decomposition(EMD) and optimally modified Log-spectral amplitude estimator(OM-LSA) algorithms are associated to separate the speech micro-vibration from the target macro motion. This combined algorithm compensates for the weakness of the EMD algorithm in denoising and the inability of the OM-LSA algorithm on signal separation, achieving separation and simultaneous acquisition of the macro motion and speech micro-vibration of a target. The experimental results indicate that using this combined algorithm, the LDV system can functionally operate within 30 m and gain a 4.21 d B promotion in the signal-to-noise ratio(SNR) relative to a traditional OM-LSA algorithm.

Composite-Light-Source Interferometer for Real-Time Micro-Vibration Measurements

A novel interferometer using a composite light source for real time measurements of micro-vibrations is proposed. The experimental results make it clear that it is insensitive to external disturbances and intensity fluctuations of the source light.

A fiber micro-vibration sensor based on single-mode fiber ring laser

A new micro-vibration sensor based on single-mode fiber ring laser is put forward. The Mach-Zehnder interferometric （MZI） detection technique is presented for interrogating laser frequency shift due to the measurand （piezoelectric transducer （PZT） is used to simulate the micro-vibration） induced laser cavity strain from both single- and multi-mode lasers. In the experiment, compared with multi-mode laser sensors, the single-mode laser sensor is proved to be a sensor with high resolution. When the PZT is driven by the analog signal （0.03 rad near 2 kHz）, the signal-to-noise ratio （SNR） of output signal from the single-mode laser sensor is close to 55 dB and the sensitivity of the sensor is about 5 ×10^-5 rad/Hz1/2.

Enhanced micro-vibration sensitive high-damping capacity and mechanical strength achieved in AI matrix composites reinforced with garnet-like lithium electrolyte

A novel micro-vibration sensitive-type high-damping AI matrix composites reinforced with Li7-xLa3Zr2-xNbxO12 （LLZNO, x = 0.25） was designed and prepared using an advanced spark plasma sintering （SPS） technique. The damping capacity and mechanical properties of LLZNO/AI composites （LLZNO content： 0-40 wt.%） were found to be greatly improved by the LLZNO addition. The maximum damping capacity and the ultimate tensile strength （UTS） of LLZNO/AI composite can be respectively up to 0.033 and 101.2 MPa in the case of 20 wt.% LLZNO addition. The enhancement of damping and mechanical properties of the composites was ascribed to the intrinsic high-damping capacity and strengthening effects of hard LLZNO particulate. This investigation provides a new insight to sensitively suppress micro-vibration of payloads in the aerospace environment.

Source Quantitative Identification by Reference-Based Cubic Blind Deconvolution Algorithm

The semi-blind deconvolution algorithm improves the separation accuracy by introducing reference information.However,the separation performance depends largely on the construction of reference signals.To improve the robustness of the semi-blind deconvolution algorithm to the reference signals and the convergence speed,the reference-based cubic blind deconvolution algorithm is proposed in this paper.The proposed algorithm can be combined with the contribution evaluation to provide trustworthy guidance for suppressing satellite micro-vibration.The normalized reference-based cubic contrast function is proposed and the validity of the new contrast function is theoretically proved.By deriving the optimal step size of gradient iteration under the new contrast function,we propose an efficient adaptive step optimization method.Furthermore,the contribution evaluation method based on vector projection is presented to implement the source contribution evaluation.Numerical simulation analysis is carried out to validate the availability and superiority of this method.Further tests given by the simulated satellite experiment and satellite ground experiment also confirm the effectiveness.The signals of control moment gyroscope and flywheel were extracted,respectively,and the contribution evaluation of vibration sources to the sensitive load area was realized.This research proposes a more accurate and robust algorithm for the source separation and provides an effective tool for the quantitative identification of the mechanical vibration sources.

Fractional nonlinear energy sinks

The cubic or third-power(TP)nonlinear energy sink(NES)has been proven to be an effective method for vibration suppression,owing to the occurrence of targeted energy transfer(TET).However,TET is unable to be triggered by the low initial energy input,and thus the TP NES would get failed under low-amplitude vibration.To resolve this issue,a new type of NES with fractional nonlinearity,e.g.,one-third-power(OTP)nonlinearity,is proposed.The dynamic behaviors of a linear oscillator(LO)with an OTP NES are investigated numerically,and then both the TET feature and the vibration attenuation performance are evaluated.Moreover,an analogy circuit is established,and the circuit simulations are carried out to verify the design concept of the OTP NES.It is found that the threshold for TET of the OTP NES is two orders of magnitude smaller than that of the TP NES.The parametric analysis shows that a heavier mass or a lower stiffness coefficient of the NES is beneficial to the occurrence of TET in the OTP NES system.Additionally,significant energy transfer is usually accompanied with efficient energy dissipation.Consequently,the OTP NES can realize TET under low initial input energy,which should be a promising approach for micro-vibration suppression.

Non-Invasive Vibration-Stress of the Cirrhotic Liver of Patients Waiting for Transplantation Induces of Circulating CD133+ Stem Lymphocytes Committed Phenotypically toward the Liver

Background: Numerous studies of tissues’ regeneration have confessed the recovery of damaged liver by hematopoietic stem cells. The cells act not only by cell replacement in the target organ but also by delivering trophic factors that support endogenous liver regeneration. A little is known of how organ-derived signals recruit such committed cells into circulation. Objective: We investigated the roles of noninvasive mechanical percutaneous stress of cirrhotic human liver in numbers fluctuation of trophic, liver-specific alpha-fetoprotein-positive fraction of CD133-positive hematopoietic stem cells in lymphocytes of patients waiting for liver transplantation. Methods: To promote in blood the number of the alpha-fetoprotein-positive fraction of CD133-positive hematopoietic stem cells, committed to liver’ tissue, we activated mechanically the cirrhotic liver of patient by transcutaneous micro vibration received from skin-contacted electro-magnetic vibraphones generated mechanical pulses with amplitude 10 μm and smoothly changing frequency from 0.03 kHz to 18 kHz and back forth during one cycle duration 1 minute. The number of the alpha-fetoprotein-positive fraction of CD133-positive hematopoietic stem cells in lymphocytes of potential recipients was controlled by flow cytometry before and during daily sonication of skin area, which corresponds to liver projection on it. The 15 minutes cyclic sonication of the liver area performed daily for three weeks. Results: The sonication increased significantly averaged number of liver-specific alpha-fetoprotein-positive CD133-positive blood lymphocytes in 2 - 3 times compared to a base lane. The second similar sonication, the same zone after three weeks break showed differences with baseline, but it was statistically insignificant. The result was specifically related to the liver as it showed the control sonication of the backbone’s projection on the skin of a separate group of patients with cirrhotic liver from the waiting list. Conclusion: The stem cells committed to the liver recruit from the bone marrow into circulation, when organ mechanically stresses and secretes specific humoral signals to provoke of lymphopoiesis on host liver repair.

Analytical Modeling of Vibration of Micropolar Plates

This paper presents an extension of mathematical static model to dynamic problems of micropolar elastic plates, recently developed by the authors. The dynamic model is based on the generalization of Hellinger-Prange-Reissner (HPR) variational principle for the linearized micropolar (Cosserat) elastodynamics. The vibration model incorporates high accuracy assumptions of the micropolar plate deformation. The computations predict additional natural frequencies, related with the material microstructure. These results are consistent with the size-effect principle known from the micropolar plate deformation. The classic Mindlin-Reissner plate resonance frequencies appear as a limiting case for homogeneous materials with no microstructure.

Progress on the use of satellite technology for gravity exploration

In this paper, the technological progress on Chinese gravity exploration satellites is presented. Novel features such as ultra-stable structure, high accurate thermal control, drag-free and attitude control, micro-thrusters, aerodynamic configuration, the ability to perform micro-vibration analyses, microwave ranging system and mass center trimmer are described.

Recent advances in precision measurement & pointing control of spacecraft

There exists an increasing need for precision measurement&pointing control and extreme motion stability for current and future space systems,e.g.,Ultra-Performance Spacecraft(UPS).Some notable technologies of realizing Ultra-Pointing(UP)ability have been developed particularly for Ultra-accuracy Ultra-stability Ultra-agility(3 U)spacecraft over recent decades.Usually,Multilevel Compound Pointing Control Techniques(MCPCTs)are deployed in aerospace engineering,especially in astronomical observation satellites and Earth observation satellites.Modern controllers and/or algorithms,which are a key factor of MCPCTs for 3 U spacecraft,especially the jitter phenomena that commonly exist in a UPS Pointing Control System(PCS),have also been effectively used in some UP spacecraft for a number of years.Micro-vibration suppression approaches,however,are often proposed to deal with low-level mechanical vibration or disturbance in the microgravity environment that is common for UPS.This latter approach potentially is one of the most practical UP techniques for 3 U tasks.Some emerging advanced Disturbance-Free Payload(DFP)satellites that exploit the benefits of non-contact actuators have also been reported in the literature.This represents an interesting and highly promising approach for solving some challenging problems in the area.This paper serves as a state-of-the-art review of UP technologies and/or methods which have been developed,mainly over the last decade,specifically for or potentially could be used for 3 U spacecraft pointing control.The problems discussed in this paper are of reference significance to UPS and millisecond optical sensors,which are involved in Gaofeng Project,deep space exploration,manned space flight,and gravitational wave detection.