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In the current paper, hygro-thermo-magnetically induced vibrations of small-scale viscoelastic tubes containing flow with a spin motion under gravity and tangential loads are analyzed by including surface effects. The dynamic equations are derived in the framework of the modified nonlocal elasticity theory (NET) and Rayleigh beam model. The Galerkin method and Laplace transformation are implemented to solve model equations. Vibration frequencies, stability boundaries, and Campbell diagrams of the system are acquired. Impacts of influential parameters such as scale rotary inertia factor, scale parameter, viscoelastic materials, gravity and tangential loads, flow and spin velocities, geometrical properties, and environmental conditions on the stability of the structure are examined. Also, the obtained results are compared for the Rayleigh and Euler-Bernoulli (EB) beam models. The golden results of this work are that by fine-adjusting the scale parameter and magnetic intensity in the system, destructive effects of hygro-thermal loads can be dampened. Besides, the increment of the rotary inertia factor and nanotube thickness induces destabilizing effect on the system. [ABSTRACT FROM AUTHOR]

Compaction uniformity is essential to the successful performance of asphalt pavement. Therefore, understanding the characteristic and full evaluation on the overall density distribution in field construction is necessary. An available method capable to assess compaction uniformity of the hot paving layer was proposed by considering both longitudinal and transverse density distribution. Field tests of density distribution behind pavers and rollers were conducted on two test sections, respectively. Then, the quantitative evaluation indexes of uniformity (i.e. the range (R), coefficient of variation (CV), repeatability standard deviation in detection track (Sr), etc.) were used to analyse compaction uniformity and the severity of non-uniformity of the asphalt mat. Moreover, the uniformity variation from paving to rolling was evaluated through the tests and a compaction uniformity model. Results indicated that rolling compaction could intensify the degree of non-uniformity of the paving mat, although all the density after rollers is higher than the density behind pavers, and simulation analysis corresponds with the test results. The uniformity of density distribution in transverse is worse than in longitudinal. Tamper seemed to be more effective than other parameters at improving the initial density, while frequency of vibrator appeared to have the most impact on transverse compaction uniformity. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study explores the subjective use of adjectives to verbally communicate vibrotactile stimulation across multiple frequencies. In total, nine different vibrotactile stimulus frequencies (10–300 Hz) were utilized, and subjective evaluation methods, which involved adjectives, were used to assess the sensory representations of the participants (18 healthy male participants; mean age, 22.9 years; standard deviation, 3.5). Sensory terms such as 'slow,' 'protruding,' and 'thick' were used as representative expressions to describe low-frequency (10–100 Hz) vibrotactile stimulations, while 'fast,' 'shallow,' and 'tickly' were used to describe high-frequency (225–300 Hz) vibrotactile stimulations. At the frequencies of 150 and 200 Hz, no characteristic word was found because there was no difference in subjective evaluation scores from other low or high frequencies. The results suggest that vibrotactile stimulation at different frequencies induce diverse sensory representations, owing to not only the motion and shape of the stimuli but also the subjective responses of the perceivers. The results of this study could be utilized in developing affective haptic devices in the future. [ABSTRACT FROM AUTHOR]

Separation of particle mixtures in micron size range is of concern to many industrial processes. The experimental work presented in this article has looked into the operational assessment of a novel vertical vibration driven particle separator by using a positron emission particle tracking (PEPT) technique. In addition to PEPT, a smoke blanket visualization technique was used to track the intestinal air movements during the course of vibration induced particle separation. Three different finely sized glass and bronze particle mixtures that formed an average particle bed heights of 20, 40, 60, 80, and 100 mm in separation cells of thickness 20 and 40 mm were used to investigate the particle separation behavior. For a range of operating conditions, the results showed in favor of low particle bed heights (below 40 mm), lower vibration frequency (30 ± 10% Hz) and a small partition separation gap size of 5 mm for optimum separation of bronze particles in the presence of air. [ABSTRACT FROM AUTHOR]

Results of investigations into the morphology and elemental and phase composition of surface layers produced by electrospark treatment of St10 steel in a gas medium using a VK8 hard cermet alloy are presented. [ABSTRACT FROM AUTHOR]

The large-amplitude free vibration analysis of a rotating annular disk of exponentially varying thickness, subjected to uniform axial pressure, is presented. The entire formulation is energy-based and uses variational principles to derive the governing equations. The study is carried out up to the onset of yielding, which occurs due to the application of two types of external loadings, namely body force due to rotation and uniform axial pressure. The results are compared for three exponential disks having the same mass. The effects of the individual loadings and their combination on the free vibration dynamic behavior are presented. [ABSTRACT FROM PUBLISHER]

To study the effect of vibration field on the electrical conductivity properties of nanocomposites, isotactic polypropylene (iPP)/multiwalled carbon nanotubes (MWCNT) composites were prepared by conventional injection molding and vibration injection molding. Results showed that the electrical conductivity of iPP/MWCNT composites was significantly promoted by vibration injection molding. Vibration injection molded samples had a percolation threshold of about 2.7 wt% compared with the threshold of about 4.5 wt% for conventional injection molded samples. The effects of test locations and vibration frequency on the electrical conductivity of composites were investigated. The samples exhibited an inhomogeneity along the injection direction. The electrical conductivity of the samples was different at different test locations and increased with increasing vibration frequency. Polarized light microscopy (PLM) results indicated that vibration injection molding can induce MWCNT aggregates to be stretched and oriented along the flow direction, which could form conductive networks and greatly enhance the electrical conductivity of iPP/MWCNT composites. [ABSTRACT FROM PUBLISHER]

Besides thermodynamic information, vibration can identify modes of a molecule by comparison of the spectroscopy and parameterize force field. By the application of group theory with the state of projection operators, a systematic method for getting the vibration model of molecule the zigzag single-walled Boron nitride nanotube (BNNT) with (8, 0) structure was proposed. The combination and their normalization coefficients of (8, 0) nanotube in C6V point group was calculated, and the effect of dielectric constants on the mechanism of these vibrations in nanotubes was studied. Normal mode analysis in chemistry was originally developed for describing the vibrational spectra of molecules, even though the interpretation is often in terms analysis is not very large. We found that in the high dielectric the frequency of vibration has alternative behavior, but by decreasing the dielectric this behavior changed to stable situation of geometry. [ABSTRACT FROM AUTHOR]

This paper presents experimental results of grinding of single-crystal silicon using a microvibration device and a diamond grindingwheel. Samples were cut from (100) silicon. The grinding direction was parallel to the [110] direction of (100) silicon. These samples were ground under the same grinding conditions but with different vibration directions, frequencies, and/or amplitudes. The surface roughness and the surface texture of all samples were analyzed for comparison. The R a , R q , and R t values and the microphotographs of the ground silicon surfaces showed the dependency of surface finish on the grinding with vibrations. Samples ground with vibrations had better surface finish compared with the silicon surfaces ground without vibrations. Out of the 12 experiments, the best surface finish was achieved when (100) silicon was ground with horizontal vibrations at a 70-Hz frequency and 6-μm amplitude perpendicular to the grinding direction. [ABSTRACT FROM AUTHOR]

The objectives of this study are to develop an ultrasonic vibration device, investigate diamond turning of an aluminium-based metal matrix composite (MMC) reinforced with SiC particles with ultrasonic vibrations applied to the cutting tool, and evaluate effects of cutting parameters on the surface finish of turned MMC samples. A low-cost, small-size vibration device was designed to mount a piezoelectric transducer and cutting tool onto a low-end CNC machine. Cutting experiments were carried out using a fractional factorial design to investigate the effects of cutting parameters. The experimental results show that surface roughness of the MMC samples cut with ultrasonic vibrations is better than that of the MMC sample cut without ultrasonic vibrations. Depth of cut and cutting speed also affect the surface finish significantly. A light dispersion phenomenon, which is not reported in other articles, is observed and explained. [ABSTRACT FROM AUTHOR]

Vibration frequency depends strongly on the propagating media and blast delay intervals. Frequency analysis is therefore important in selecting optimum blast delay intervals. The application of Fourier frequency analysis to determine the dominant frequency in ground motion is quite common. The Fourier spectra provide a complete description of the amplitudes of waveforms versus frequency, but these do not contain information regarding the time duration of these waveforms. Moreover, it is well known that damage to structures is dependent on the time duration of blasts as well as on the amplitudes and frequency of waves. Therefore, in addition to the dominant frequency of the waveform, the time duration of the waveform at that frequency must also be known. The Stockwell transform (S-transform) overcomes this difficulty in such a way that the S-transform of particle velocity records offers a means of representing the variation of spectral components with time. This paper examines the use of the S-transform for obtaining time-frequency representations of peak particle velocity records. This paper describes application of the S-transform—in conjunction with Fourier spectral analysis—to the determination of optimal delay times in the blasting process. [ABSTRACT FROM AUTHOR]