The Influences of Ultrasonic Vibrations on Laser Cladding Ni60/WC-TiO2+La2O3 Composite Coating

The optimal process parameters of ultrasonic-assisted processing were studied to further improve the molding quality and mechanical properties of Ni60/WC-TiO2+La2O3 composite coating. A single-factor experiment was used to explore the influences of ultrasonic vibration frequencies on Ni60/WC-TiO2+La2O3 composite coating. The microstructure, elemental composition, phase composition, hardness, and wear resistance of the coating were studied using scanning electron microscopy (SEM), an X-ray diffractometer (XRD), an energy spectrometer, a microhardness meter, a friction and wear tester, and other equipment. Ultrasonic vibrations significantly improved the problems of pores in the coating, and the porosity was reduced from 0.13 to 0.014%. When the vibration frequency was 32 kHz in the experiment, the aspect ratio of the coating was optimized from 2.06 to 2.48, the dilution rate increased from 5.60 to 5.79%, the hardness increased from 960.25 to 988.45 HZ1.0, and the friction coefficient was reduced from 0.34 to 0.27. The coating performance was significantly improved, and the research results provide a reference for preparing excellent Ni60/WC-TiC+La2O3 composite coating.

Frame vibration states identification for corn harvester based on joint improved empirical mode decomposition - Support vector machine method

The frame of corn harvester is prone to vibration bending and torsional deformation due to the vibration caused by field road bumps and fluctuations. It poses a serious challenge to the reliability of machinery. Therefore it is critical to explore the vibration mechanism, and to identify the vibration states under different working conditions. To address the above problem, a vibration state identification method is proposed in this paper. An improved empirical mode decomposition (EMD) algorithm was used to decrease noise for signals of high noise and non-stationary vibration in the field. The support vector machine (SVM) model was used for identification of frame vibration states under different working conditions. The results showed that: (1) an improved EMD algorithm could effectively reduce noise interference and restore the effective information of the original signal. (2) based on improved EMD - SVM method identify the vibration states of the frame with the accuracy of 99.21%. (3) The corn ears in grain tank were not sensitive to low order vibration, but had an absorption effect on high order vibration. The proposed method has the potential to be applied for accurately identifying vibration state and improving frame safety.

Effects of Low-Frequency Whole-Body Vibration on Muscle Activation, Fatigue, and Oxygen Consumption in Healthy Young Adults: A Single-Group Repeated-Measures Controlled Trial

CONTEXT

Whole-body vibration (WBV) training improves muscle strength and balance. Few studies have focused on the effects of WBV frequencies below 30 Hz. We aimed to investigate the effect of low-frequency WBV training on muscle activity, fatigue recovery, and oxygen consumption (VO2).

DESIGN

Prospective single-group, repeated-measures study.

METHODS

In this controlled laboratory setting study, 20 healthy adults (age 23.26 [1.66] y) performed half squats at 0, 4, 6, 8, 12, 16, 20, 24, and 30-Hz WBV. Muscle activity was evaluated using the root mean square and peak electromyography amplitude of 6 muscles (iliocostalis, rectus abdominis, rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius) obtained via surface electromyography. VO2 was measured during the squats using a gas analyzer, and fatigue recovery was evaluated using measurements of lactate after the squats and after a recovery period. Statistical significance was set at P < .05, and analysis of variance was conducted to determine differences in muscle activity, fatigue, recovery, and VO2, with post hoc analyses as appropriate.

RESULTS

Of the 6 muscles measured, the muscle activity of the gastrocnemius alone significantly increased from 0 Hz at 4, 8, 12, 16, 24, and 30 Hz based on the root mean square values and at 4, 8, 12, and 30 Hz based on the peak electromyography amplitude values. There were no significant differences in the other muscles. There were no significant differences in VO2 or in lactate levels.

CONCLUSIONS

Low-frequency WBV during squat exercises significantly increased the activity of the gastrocnemius medialis only at specific frequencies in healthy young adults. Low-frequency WBV is safe and has the potential to increase muscle activity.

The Osteogenic Differentiation of Human Dental Pulp Stem Cells through G0/G1 Arrest and the p-ERK/Runx-2 Pathway by Sonic Vibration

Mechanical/physical stimulations modulate tissue metabolism, and this process involves multiple cellular mechanisms, including the secretion of growth factors and the activation of mechano-physically sensitive kinases. Cells and tissue can be modulated through specific vibration-induced changes in cell activity, which depend on the vibration frequency and occur via differential gene expression. However, there are few reports about the effects of medium-magnitude (1.12 g) sonic vibration on the osteogenic differentiation of human dental pulp stem cells (HDPSCs). In this study, we investigated whether medium-magnitude (1.12 g) sonic vibration with a frequency of 30, 45, or 100 Hz could affect the osteogenic differentiation of HDPSCs. Their cell morphology changed to a cuboidal shape at 45 Hz and 100 Hz, but the cells in the other groups were elongated. FACS analysis showed decreased CD 73, CD 90, and CD 105 expression at 45 Hz and 100 Hz. Additionally, the proportions of cells in the G0/G1 phase in the control, 30 Hz, 45 Hz, and 100 Hz groups after vibration were 60.7%, 65.9%, 68.3%, and 66.7%, respectively. The mRNA levels of osteogenic-specific markers, including osteonectin, osteocalcin, BMP-2, ALP, and Runx-2, increased at 45 and 100 Hz, and the ALP and calcium content was elevated in the vibration groups compared with those in the control. Additionally, the western blotting results showed that p-ERK, BSP, osteoprotegerin, and osteonectin proteins were upregulated at 45 Hz compared with the other groups. The vibration groups showed higher ALP and calcium content than the control. Vibration, especially at 100 Hz, increased the number of calcified nodes relative to the control group, as evidenced by von Kossa staining. Immunohistochemical staining demonstrated that type I and III collagen, osteonectin, and osteopontin were upregulated at 45 Hz and 100 Hz. These results suggest that medium magnitude vibration at 45 Hz induces the G0/G1 arrest of HDPSCs through the p-ERK/Runx-2 pathway and can serve as a potent stimulator of differentiation and extracellular matrix production.

A Study on the Classification Effect of sEMG Signals in Different Vibration Environments Based on the LDA Algorithm

Myoelectric prosthesis has become an important aid to disabled people. Although it can help people to recover to a nearly normal life, whether they can adapt to severe working conditions is a subject that is yet to be studied. Generally speaking, the working environment is dominated by vibration. This paper takes the gripping action as its research object, and focuses on the identification of grasping intentions under different vibration frequencies in different working conditions. In this way, the possibility of the disabled people who wear myoelectric prosthesis to work in various vibration environment is studied. In this paper, an experimental test platform capable of simulating 0–50 Hz vibration was established, and the Surface Electromyography (sEMG) signals of the human arm in the open and grasping states were obtained through the MP160 physiological record analysis system. Considering the reliability of human intention recognition and the rapidity of algorithm processing, six different time-domain features and the Linear Discriminant Analysis (LDA) classifier were selected as the sEMG signal feature extraction and recognition algorithms in this paper. When two kinds of features, Zero Crossing (ZC) and Root Mean Square (RMS), were used as input, the accuracy of LDA algorithm can reach 96.9%. When three features, RMS, Minimum Value (MIN), and Variance (VAR), were used as inputs, the accuracy of the LDA algorithm can reach 98.0%. When the six features were used as inputs, the accuracy of the LDA algorithm reached 98.4%. In the analysis of different vibration frequencies, it was found that when the vibration frequency reached 20 Hz, the average accuracy of the LDA algorithm in recognizing actions was low, while at 0 Hz, 40 Hz and 50 Hz, the average accuracy was relatively high. This is of great significance in guiding disabled people to work in a vibration environment in the future.

Effect of Different Local Vibration Frequencies on the Multiscale Regularity of Plantar Skin Blood Flow

Local vibration has shown promise in improving skin blood flow (SBF). However, there is no consensus on the selection of the best vibration frequency. An important reason may be that previous studies utilized time- and frequency-domain parameters to characterize vibration-induced SBF responses. These parameters are unable to characterize the structural features of the SBF response to local vibrations, thus contributing to the inconsistent findings seen in vibration research. The objective of this study was to provide evidence that nonlinear dynamics of SBF responses would be an important aspect for assessing the effect of local vibration on SBF. Local vibrations at 100 Hz, 35 Hz, and 0 Hz (sham vibration) with an amplitude of 1 mm were randomly applied to the right first metatarsal head of 12 healthy participants for 10 min. SBF at the same site was measured for 10 min before and after local vibration. The degree of regularity of SBF was quantified using a multiscale sample entropy algorithm. The results showed that 100 Hz vibration significantly increased multiscale regularity of SBF but 35 Hz and 0 Hz (sham vibration) did not. The significant increase of regularity of SBF after 100 Hz vibration was mainly attributed to increased regularity of SBF oscillations within the frequency interval at 0.0095–0.15 Hz. These findings support the use of multiscale regularity to assess effectiveness of local vibration on improving skin blood flow.

The acute effects of different frequencies of whole-body vibration on arterial stiffness

Whole-body vibration (WBV) can decrease arterial stiffness, but the effects of low-frequency WBV on arterial stiffness are not known. The aim of this study was to clarify the acute effects on arterial stiffness of WBV by vibration frequency. This study involved 9 healthy men (age: 31 ± 7 years). Each WBV session involved 3 sets of 4 different vibrations (0 Hz [control], 12 Hz, 20 Hz, 30 Hz) lasting 60 s with a 60-s inter-session rest interval. During WBV, the participants adopted a static squat position with their knees bent. An automatic oscillometric device was used to measure brachial-ankle pulse wave velocity (baPWV) before (baseline) and 5, 15, and 30 min after WBV. There was a significant decrease in baPWV from baseline at 30 min (P = .02) after WBV at 30 Hz. However, there was no change in baPWV at any time points after WBV at 0 (control), 12, and 20 Hz. These results suggested that low-frequency WBV does not affect arterial stiffness.

Transparent Film-Type Vibrotactile Actuator Array and Its Haptic Rendering Using Beat Phenomenon

The most important thing in a thin and soft haptic module with an electroactive polymer actuator array is to increase its vibrotactile amplitude and to create a variety of vibrotactile sensations. In this paper, we introduce a thin film-type electroactive polymer actuator array capable of stimulating two types of human mechanoreceptors simultaneously, and we present a haptic rendering method that maximizes the actuators’ vibrational force without improving the array’s haptic performance. The increase in vibrational amplitude of the soft electroactive polymer actuator array is achieved by creating a beat vibration, which is an interference pattern of two vibrations with slightly different frequencies. The textures of a target object are translated into haptic stimuli using the proposed method. We conducted qualitative and quantitative experiments to evaluate the performance of the proposed rendering method. The results showed that this method not only amplifies the vibration’s amplitude but also haptically simulates various objects’ surfaces.

Development of a New Ultra-High-Precision Magnetic Abrasive Finishing for Wire Material Using a Rotating Magnetic Field

In this paper, we propose a new ultra-high-precision magnetic abrasive finishing method for wire material which is considered to be difficult with the existing finishing process. The processing method uses a rotating magnetic field system with unbonded magnetic abrasive type. It is believed that this process can efficiently perform the ultra-high-precision finishing for producing a smooth surface finish and removing a diameter of wire material. For such a processing improvement, the following parameters are considered; rotational speed of rotating magnetic field, vibration frequency of wire material, and unbonded magnetic abrasive grain size. In order to evaluate the performance of the new finishing process for the wire material, the American Iron and Steel Institute (AISI) 1085 steel wire was used as the wire workpiece. The experimental results showed that the original surface roughness of AISI 1085 steel wire was enhanced from 0.25 µm to 0.02 µm for 60 s at 800 rpm of rotational speed. Also, the performance of the removed diameter was excellent. As the result, a new ultra-high-precision magnetic abrasive finishing using a rotating magnetic field with unbonded magnetic abrasive type could be successfully adopted for improving the surface roughness and removing the diameter of AISI 1085 steel wire material.