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The article focuses on the research of processes of summation of ultrasonic vibrations of individual Langevin transducers symmetrically arranged on a common summator. This design could be used to solve the problem of increasing the power of a high-frequency ultrasonic radiator by means of the summation of the vibrations of individual Langevin transducers. The results of the presented theoretical and experimental investigations supported the possibility of summation of symmetrical diametrical vibrations when they are transformed into longitudinal vibrations. As a result, a new design scheme for high-frequency radiator construction was developed that provides symmetry and uniformity of vibration amplitude distribution of piezoceramic elements. This made it possible to eliminate the damage of piezoceramic elements. The article establishes that an acoustic power (continuous mode) of 1450 W at an efficiency of 78% is achieved when the vibrations from 9 to 11 of symmetrically arranged Langevin transducers at a resonant frequency of 30.05 kHz with an amplitude of 26 µm are summed. The use of this ultrasonic high-frequency radiator with increased power will provide intensification of processes in various areas of industry. [ABSTRACT FROM AUTHOR]

The motion of a heavy rigid body is studied in the case when one of its points (the suspension point) undergoes high-frequency horizontal vibrations and the body mass geometry for this point corresponds to the Kovalevskaya case. The problem is examined using an approximate autonomous system of differential equations represented in the Hamiltonian form. Particular body motions are studied: pendulum-type motions and rotations around the principle axis of inertia oriented horizontally, which is either a dynamic-symmetry axis or an axis located in the equatorial inertia plane. The radius vector of the center of mass of the body relative to the suspension point performs pendulum-type motions in a vertical plane containing the vibration axis (longitudinal motions) or perpendicular to this axis (transverse motions). This publication completes the linear analysis of the orbital stability of the described pendulum-type motions with consideration for spatial perturbations, which was commenced earlier. The problem has been reduced to an equivalent problem of the stability of the trivial equilibrium of a reduced non-autonomous system with two degrees of freedom. In the regions of linear-approximation stability, a detailed nonlinear analysis of the orbital stability has been carried out. Criteria of the stability for most (in the sense of the Lebesgue measure) initial conditions and the formal stability criteria have been checked and cases of fourth-order resonances have been explored. [ABSTRACT FROM AUTHOR]

Data-driven texture modeling and rendering has pushed the limit of realism in haptics. However, the lack of haptic texture databases, difficulties of model interpolation and expansion, and the complexity of real textures prevent data-driven methods from capturing a large variety of textures and from customizing models to suit specific output hardware or user needs. This work proposes an interactive texture generation and search framework driven by user input. We design a GAN-based texture model generator, which can create a wide range of texture models using Auto-Regressive processes. Our interactive texture search method, which we call “preference-driven,” follows an evolutionary strategy given guidance from user's preferred feedback within a set of generated texture models. We implemented this framework on a 3D haptic device and conducted a two-phase user study to evaluate the efficiency and accuracy of our method for previously unmodeled textures. The results showed that by comparing the feel of real and generated virtual textures, users can follow an evolutionary process to efficiently find a virtual texture model that matched or exceeded the realism of a data-driven model. Furthermore, for 4 out of 5 real textures, $\geq$ 80% of the preference-driven models from participants were rated comparable to the data-driven models. [ABSTRACT FROM AUTHOR]

We have investigated the influences of high-frequency vibration (HFV) superimposed onto the monotonic uniaxial tension in single-crystal aluminum (Al) specimens by molecular dynamics simulations. It was found that HFV induces softening, i.e., reduction in peak stress. Similar to previous experimental results, the softening increases with the increasing HFV amplitude. Dependences on lattice orientation, tensile strain rate, and a preset notch are considered. Lattice orientation plays an important role in peak stress and plasticity. The evolution of the atomic structure reveals that dislocations have enough time to annihilate under a lower tensile strain rate, resulting in strong ups and downs in the strain–stress curves. Under a higher strain rate, newly appearing dislocations interact with previous ones before the latter annihilate, densifying the dislocation network. As a result, further dislocation motions and annihilations are considerably impeded, leading to a relatively smooth flow stage. Furthermore, by modifying the propagation direction of shear bands, a preset notch can strengthen the peak tensile stress under low-level amplitude HFVs. [ABSTRACT FROM AUTHOR]

The objective of this article was to conduct a systematic review of the literature to contrast the existing evidence on the effect of mechanical vibrations, either high or low frequency, as an alternative to accelerate orthodontic tooth movement in humans. A literature search from 2010 to June 2021 was conducted in the electronic databases: PubMed, NCBI, Google Scholar, EBSCO, Cochrane, and Ovid, using the eligibility criteria to identify the studies. Only randomized clinical trials (RCT) were included. The certainty of the evidence was assessed using the GRADE tool and the risk of bias (RoB) in individual studies was evaluated according to the Cochrane bias risk tool. Fifteen RTCs were included for final review. Overall, the RoB was classified as low (3), moderate (5), and high (7). Three articles with low RoB, four with moderate RoB, and four with high RoB found no significant effect in the use of vibrations on orthodontic movement. Only four articles, three of them with high RoB and one with moderate RoB, found that mechanical vibrations are effective at accelerating orthodontic tooth movement. The results seemed to indicate that there is no evidence that vibratory stimuli can increase the rate of dental movement or reduce neither the time of dental alignment nor canine retraction during orthodontic treatment. It is important to note that a greater number of high-quality randomized controlled trials are urgently needed. [ABSTRACT FROM AUTHOR]

The article focuses on the research of processes of summation of ultrasonic vibrations of individual Langevin transducers symmetrically arranged on a common summator. This design could be used to solve the problem of increasing the power of a high-frequency ultrasonic radiator by means of the summation of the vibrations of individual Langevin transducers. The results of the presented theoretical and experimental investigations supported the possibility of summation of symmetrical diametrical vibrations when they are transformed into longitudinal vibrations. As a result, a new design scheme for high-frequency radiator construction was developed that provides symmetry and uniformity of vibration amplitude distribution of piezoceramic elements. This made it possible to eliminate the damage of piezoceramic elements. The article establishes that an acoustic power (continuous mode) of 1450 W at an efficiency of 78% is achieved when the vibrations from 9 to 11 of symmetrically arranged Langevin transducers at a resonant frequency of 30.05 kHz with an amplitude of 26 µm are summed. The use of this ultrasonic high-frequency radiator with increased power will provide intensification of processes in various areas of industry.

Kinesthetic haptic devices are designed primarily to display quasistatic and low-bandwidth forces and moments. Existing methods for vibrotactile display sometimes introduce haptic and/or audio artifacts. In this article, we propose a method to display vibrotactile stimulus signals of moderate to high frequency (20–500 Hz) using kinesthetic haptic devices with a standard 1 kHz haptic update rate. Our method combines symmetric square-wave signals whose periods are even multiples of the haptic update period with asymmetric square-wave signals whose periods are odd multiples of the haptic update period, while ensuring that the positive and negative impulses are balanced in both cases, and utilizing the just noticeable difference in frequency discrimination to avoid the need to display other frequencies. For frequencies at which the above method is insufficient, corresponding to a small band near 400 Hz for a 1 kHz update rate, we utilize a signal-mixing method. Our complete method is then extended to render haptic gratings by measuring scanning velocity, converting the local spatial frequency to its equivalent instantaneous temporal frequency, and displaying a single full-period vibration event. In a series of human-subject studies, we showed that our proposed method is preferred over existing methods for vibrotactile display of signals with relatively high-frequency content. [ABSTRACT FROM AUTHOR]

In the framework of the two-phase theory of nonlocal elasticity we study free high-frequency vibrations of nanobeams with varying cross section. Considering the Helmholtz kernel in the constitutive equation, we reduce the original integro-differential equation to an equivalent six-order differential equation with variable coefficients and derive the pair of additional boundary conditions accounting for the nonlocal edge effects. Applying WKB method, a solution of the boundary-value problem is constructed in the form of superposition of the outer expansion and edge effect integrals with high variability along the beam axis. As an example, a clamped nanobeam with a shape matching to the shape of a slab waveguide in a photonic crystal beam laser is considered. The derived relations for natural frequencies and performed calculations revealed strong effect of both the nonlocal model fraction and the cross-section variability on the correction to natural frequencies calculated within the classical beam theory [ABSTRACT FROM AUTHOR]

In our recent article, we found a general quadratic weighting function to predict how a six-dimensional (6D) vibrotactile stimulus rendered at the haptic interaction point (HIP) of a kinesthetic haptic interface, with the stylus held in a precision pen-hold grasp, is mapped to an equivalent one-dimensional (1D) stimulus that is normalized by the detection threshold. However, in that work we did not constrain the weighting function to be positive semidefinite, and as a result, the model will not generalize well to all future 6D inputs. In this addendum, we reconsider the original data set, incorporating the positive-semidefinite constraint. We find that as few as four independent parameters are required to describe the coupling, and the model has one fewer coupling term than originally proposed. We also describe the process of fitting a positive-semidefinite function to a new stylus at some specific excitation frequency. [ABSTRACT FROM AUTHOR]

We have investigated the influences of high-frequency vibration (HFV) superimposed onto the monotonic uniaxial tension in single-crystal aluminum (Al) specimens by molecular dynamics simulations. It was found that HFV induces softening, i.e., reduction in peak stress. Similar to previous experimental results, the softening increases with the increasing HFV amplitude. Dependences on lattice orientation, tensile strain rate, and a preset notch are considered. Lattice orientation plays an important role in peak stress and plasticity. The evolution of the atomic structure reveals that dislocations have enough time to annihilate under a lower tensile strain rate, resulting in strong ups and downs in the strain–stress curves. Under a higher strain rate, newly appearing dislocations interact with previous ones before the latter annihilate, densifying the dislocation network. As a result, further dislocation motions and annihilations are considerably impeded, leading to a relatively smooth flow stage. Furthermore, by modifying the propagation direction of shear bands, a preset notch can strengthen the peak tensile stress under low-level amplitude HFVs.

A new model of laminar vibrational combustion is constructed relying on a thermodynamic analysis of the combustion process. Two combustion modes, detonation and deflagration, are modeled. The nature of their origin depending on the structure of the standard chemical potential is established, and a numerical experiment concerning the onset of these combustion modes is carried out. By controlling the velocity of the passive component at the inlet, the critical value of the standard chemical potential is identified at which there appear high-frequency vibrations leading to blow-up. [ABSTRACT FROM AUTHOR]

The objective of this article was to conduct a systematic review of the literature to contrast the existing evidence on the effect of mechanical vibrations, either high or low frequency, as an alternative to accelerate orthodontic tooth movement in humans. A literature search from 2010 to June 2021 was conducted in the electronic databases: PubMed, NCBI, Google Scholar, EBSCO, Cochrane, and Ovid, using the eligibility criteria to identify the studies. Only randomized clinical trials (RCT) were included. The certainty of the evidence was assessed using the GRADE tool and the risk of bias (RoB) in individual studies was evaluated according to the Cochrane bias risk tool. Fifteen RTCs were included for final review. Overall, the RoB was classified as low (3), moderate (5), and high (7). Three articles with low RoB, four with moderate RoB, and four with high RoB found no significant effect in the use of vibrations on orthodontic movement. Only four articles, three of them with high RoB and one with moderate RoB, found that mechanical vibrations are effective at accelerating orthodontic tooth movement. The results seemed to indicate that there is no evidence that vibratory stimuli can increase the rate of dental movement or reduce neither the time of dental alignment nor canine retraction during orthodontic treatment. It is important to note that a greater number of high-quality randomized controlled trials are urgently needed.

Tip-Tilt mirrors play an important role in astronomical telescopes requiring the tracking performance at the level of microradian or sub-microradian. However, the closed-loop performance suffers a lot from the low-sample rate and time delay of image sensors. Especially, this issue is under the condition of vibrations, because dynamic behaviors are complex and the models are difficult to be obtained accurately. Another challenging issue comes from the measurement of vibrations and its extraction for the closed-loop control. This paper proposes a new method based on an add-on controller of the Tip-Tilt mirror to mitigate telescope vibrations. The proposed method only uses Tip-Tilt errors from an image sensor to implement a disturbance observer, which is not being restricted by an accurate model. As a result, the closed-loop performance can be optimized by designing of a proper Q-filter. To suppress the low-frequency and high-frequency vibrations, a novel Q-filter combining a lowpass filter and a bandpass filter is proposed here. The improved control method is validated by both simulation and experiment in the tip-tilt mirror control system under the condition of vibrations. • An improved add-on controller is presented to reject vibrations. • Low-frequency and high-frequency vibrations can be rejected simultaneously. • A new design technique of Q-filter based on sensitivity function is proposed. • Vibration rejection is improved without high loop bandwidth. [ABSTRACT FROM AUTHOR]

The study aimed to assess the hand-arm vibration (HAV), noise exposure, and shift in hearing threshold (SHT) due to the prolonged use of hand tools used in three different handicraft occupations. Data about HAV and noise level were collected under actual work conditions. Thirty male participants volunteered to participate in this cross-sectional experiment. Audiometric tests were conducted to compare hearing threshold between the three groups. The association of hearing threshold at nine-pitch frequencies among the occupations was detected using post hoc multiple comparisons. The estimate of total value of frequency-weighted vibrations in the occupations, except carpet alignment, was quite high. The workers were exposed to noise levels ranging from 87.2 dB(A) to 100.4 dB(A). Most workers exhibit moderate to higher SHT in the frequency range 1500–6000 Hz. The contribution of the study is to propose the insight to develop work system interventions that could prevail over HAV and noise. [ABSTRACT FROM AUTHOR]

The human hand detects high-frequency vibrations in all directions but cannot distinguish the direction, which suggests a multi-dimensional vibrotactile stimulus is haptically equivalent to some one-dimensional (1D) stimulus. In this article, we explore how a 6D vibrotactile stimulus rendered at the haptic interaction point (HIP) of a kinesthetic haptic interface, with the stylus held in a precision pen-hold grasp, is mapped to an equivalent 1D stimulus normalized by the detection threshold. We gather a large human-subjects data set in which we determine detection thresholds for 45 distinct combinations of three orthogonal forces and three orthogonal torques rendered at the HIP, at a single frequency of 108 Hz corresponding to the peak sensitivity in our prior study. Using this data set, we find a general quadratic weighting function to predict the 1D normalized stimulus for a given 6D vibrotactile stimulus. We find that including just seven (out of a possible 21) independent parameters in the symmetric weighting matrix is sufficient to capture the non-obvious coupling between forces and torques rendered at the HIP for dimensional reduction from 6D to 1D. [ABSTRACT FROM AUTHOR]

Quasi-steady and transient rolling contact of a driving wheelset over tangent and curved tracks at a speed up to 500 km/h is simulated using an explicit finite element approach to derive creep curves. Quasi-steady curves corresponding to smooth wheel and rail are compared to those from traditional theories implying the steady rolling assumption for validation. Transient curves in the presence of rail corrugation with a wavelength of 10 ∼ 1000 mm are further analyzed to study the influence of middle/high-frequency vibrations. Cases where transient effects must be considered or traditional theories are inapplicable are identified. • The transient rolling contact model is validated in the creep curve. • Transient creep curves under middle/high-frequency vibrations are derived. • Variations of the transient curve with speed and irregularity wavelength identified. • Cases where the transient effects must be considered are identified. • Applicability of traditional rolling contact theories is discussed. [ABSTRACT FROM AUTHOR]

The aim of the study was to investigate the occupational use of low-cost intervention for carpet trimming occupation. This study quantifies the effect of hand-arm vibration and noise exposure to loss in hearing threshold among trimming workers. Ten male participants (right handed) involved in carpet trimming volunteered to participate in this interventional experiment. The participants were queried about the usability of prototype handle based on their subjective perception evaluated through the use of scoresheet/questionnaire. Results demonstrated that the handle intervention reduced the total value of root mean square frequency-weighted vibrations by more than 40% when compared with the conventional handle. The workers were exposed to noise levels ranging from 87.2 to 91.8 dB(A) (mean 89.55 dB(A)). They exhibit mild-to-moderate hearing impairment in the frequency range of 3000–6000 Hz. Based on this preliminary work, we have found that prototype handle was effective in curtailing hand-arm vibration. The prototype handle showed a positive effect on the usability ratings. More practical applications should be explored to prevail the combined effect of hand-arm vibration and noise. [ABSTRACT FROM AUTHOR]

Based on the thermovibrational convection equations, we have investigated the structure of the averaged plane-parallel convective flow in a plane vertical layer of Williamson fluid executing high-frequency linearly polarized vibrations along the layer. We show that as the vibrations are intensified, the nonlinear viscous properties of a pseudoplastic fluid cease to affect the structure and intensity of its main flow, and it becomes similar to a flow of ordinary Newtonian fluid. The linear problem of stability of an averaged plane-parallel flow of pseudoplastic Williamson fluid has been formulated and solved for the case of longitudinal high-frequency linearly polarized vibrations for small periodic perturbations along the layer. Numerical calculations have shown that, as in a Newtonian fluid, the monotonic hydrodynamic perturbations are most dangerous at low Prandtl numbers. As the Prandtl number increases, the thermal instability modes begin to exert an undesirable effect. An enhancement of pseudoplastic fluid properties leads to destabilization of the main flow for both types of perturbations. Similarly to a Newtonian fluid, an additional vibrational instability mode to which small Grashof numbers correspond appears in the presence of vibrations. The influence of this vibrational mode on the stability of the main flow is determined by the vibration frequency and the temperature gradient. An intensification of the vibrations destabilizes the flow for all of the investigated instability modes. For a given set of rheological parameters of the Williamson model, there are critical values of the modified and vibrational Grashof numbers at which the averaged flow completely loses its stability with respect to the types of perturbations under consideration. Absolute destabilization of the main flow in a pseudoplastic fluid occurs at higher values of the vibrational Grashof number than those in a Newtonian fluid. [ABSTRACT FROM AUTHOR]

The onset of convection in a system of horizontal layers of a binary solution and an inhomogeneous porous medium saturated with the solution is studied. The system is subjected to high-frequency transverse vibrations in the gravity field. It is assumed that the porosity of the medium depends linearly on the vertical coordinate. The permeability is estimated by the Karman-Kozeny formula for different values of the dimensionless gradient of the porosity, mz. The convection of the fluid under the action of high-frequency vibrations in the gravity field is described using the averaging method. The linear problem of the stability of the mechanical equilibrium of the fluid is solved numerically by the shooting method. The values of the critical parameters corresponding to the convection initiation threshold are determined for the system heated from below or from above. The heating from below is distinguished by a sharp change in the character of the instability with a variation in the porosity gradient or the vibration intensity. It is shown that, when the porosity increases with depth, at mz =-0.2, the instability is caused by the development of long-wave perturbations involving the fluid and the porous layers. When the porosity decreases with depth, at mz = 0.2, the most dangerous perturbations are short-wave perturbations localized in the fluid layer. For intermediate values of the porosity gradient,-0.2< mz < 0.2, the values of the minimum Rayleigh-Darcy critical numbers, which determine the equilibrium stability threshold with respect to short-wave and long-wave disturbances, approach one another. The neutral curves are bimodal. Upon heating from below, vertical vibrations effectively suppress convection in the fluid layer; therefore, with an increase in their intensity, the transition from short-wave vibrations, which are most dangerous, to long-wave perturbations is observed. A noticeable increase in the stability threshold is observed when the porosity decreases with depth. Upon heating from above, vibrations destabilize the equilibrium in the system and lead to a reduction in the wavelength of the critical perturbations. The wavelength decreases monotonically. Its maximum change is detected in layers whose porosity increases with depth. [ABSTRACT FROM AUTHOR]

Selecting appropriate features from the vibration condition monitoring data of ball-bearings is one of the main challenges in the application of data-driven methods for remaining useful life prediction purpose. In this article, a new feature based on the high-frequency vibration of ball-bearings is proposed. The feed forward neural network will be used for training and prediction. The experimental data of the bearing accelerated life in the PROGNOSTIA test (published in PHM 2012 IEEE conference) are used to verify the method. The results obtained by applying new features are compared with those of two popular features in the time domain (RMS and kurtosis) for prognostic purpose. Applying the proposed feature shows more accurate estimation of the bearings' remaining useful life. [ABSTRACT FROM AUTHOR]

We numerically simulate the initiation of an average convective flow in a system composed of a horizontal binary fluid layer overlying a homogeneous porous layer saturated with the same fluid under gravitational field and vibration. In the layers, fixed equilibrium temperature and concentration gradients are set. The layers execute high-frequency oscillations in the vertical direction. The vibration period is small compared with characteristic timescales of the problem. The averaging method is applied to obtain vibrational convection equations. Using for computation the shooting method, a numerical investigation is carried out for an aqueous ammonium chloride solution and packed glass spheres saturated with the solution. The instability threshold is determined under two heating conditions—on heating from below and from above. When the solution is heated from below, the instability character changes abruptly with increasing solutal Rayleigh number, i.e., there is a jump-wise transition from the most dangerous shortwave perturbations localized in the fluid layer to the long-wave perturbations covering both layers. The perturbation wavelength increases by almost 10 times. Vibrations significantly stabilize the fluid equilibrium state and lead to an increase in the wavelength of its perturbations. When the fluid with the stabilizing concentration gradient is heated from below, convection can occur not only in a monotonous manner but also in an oscillatory manner. The frequency of critical oscillatory perturbations decreases by 10 times, when the long-wave instability replaces the shortwave instability. When the fluid is heated from above, only stationary convection is excited over the entire range of the examined parameters. A lower monotonic instability level is associated with the development of perturbations with longer wavelength even at a relatively large fluid layer thickness. Vibrations speed up the stationary convection onset and lead to a decrease in the wavelength of most dangerous perturbations of the motionless equilibrium state. In this case, high enough amplitudes of vibration are needed for a remarkable change in the stability threshold. The results of numerical simulation show good agreement with the data of earlier works in the limiting case of zero fluid layer thickness. [ABSTRACT FROM AUTHOR]

The convective instability and non-linear flows are considered in a horizontal, binary-mixture layer with negative Soret coupling, subjected to the high-frequency vibration whose axis is directed at an arbitrary angle to the layer boundaries. The limiting case of long-wave disturbances is studied using the perturbation method. The influence of the intensity and direction of vibration on the spatially-periodic traveling wave solution is analyzed. It is shown that the shift in the Rayleigh number range, in which the traveling wave regime exists, toward higher values is a response to a horizontal-to-vertical transition in the vibration axis orientation. The characteristics of amplitude- and phase-modulated traveling waves are obtained and discussed. [ABSTRACT FROM AUTHOR]

The paper deals with the numerical investigation of the possibilities to control convective flows in the liquid bridge in zero gravity conditions applying axial vibrations. The surface tension is assumed to be dependent both on the temperature and on the solute concentration. The free surface deformations and the curvature of the phase change surfaces are neglected but pulsational deformations of the free surface are accounted for. The first part of the paper concerns axisymmetric steady flows. The calculations show that the evolution of convective flow with the variation of thermal Marangoni number at a fixed value of the solutal Marangoni number is accompanied by the hysteresis phenomenon, which is related to the existence of two stable steady regimes in a certain parameter range. One of these regimes is thermocapillary dominated, it corresponds to the two-vortex flow, and the other is solutocapillary dominated, it corresponds to the single-vortex flow. Under vibrations, the range of the Marangoni numbers where hysteresis is observed becomes narrower and is shifted to the area of larger values. The second part of the paper concerns the stability of axisymmetric thermo-and solutocapillary flows and the transition to three-dimensional regimes. Significant mutual influence of flows generated by each process on the stability of the other is discovered. Stability maps in the parametric plane for the thermal Marangoni number, the solutal Marangoni number, are obtained for different values of vibration parameters. It is shown, that vibrations exert a stabilizing effect, increasing critical Marangoni numbers for all modes of instability. However, this effect is different for different modes and at high vibration intensity destabilization is possible. Consequently, vibrations can modify the scenario of the transition to the three-dimensional mode. [ABSTRACT FROM AUTHOR]

W pracy przedstawiono model opisujący drgania o wysokiej częstości, występujące w trakcie ciągłego walcowania blach. Model ten jest oparty na założeniu samowzbudności procesu. Zbadano wpływ parametrów klatki oraz procesu walcowania na charakter i intensywność drgań. Wyjaśniono również zjawisko powstawania na powierzchni blachy zaciemnionych pasków. Otrzymane wyniki porównano z wynikami badań.

This paper presents the design and validation of an ungrounded haptic augmented reality system that alters the roughness and friction of a rigid 3-D object. The user touches the object via a custom haptic stylus; the stylus tip is a ball mounted in a socket that has low internal friction and produces minimal vibrations, necessary conditions for creating a haptically clean interaction. We determine contact position and force using a six-axis force/torque sensor beneath the object. The object's apparent roughness and kinetic friction are altered using haptic models that we previously created from real tool-surface interaction data. The textural roughness model generates a vibration waveform in real time, which is played through a voice coil actuator. A solenoid inside the stylus applies a braking force to the ball for friction rendering. The friction model continually controls the solenoid current, setting the effective kinetic friction coefficient between the stylus tip and object surface to values between 0.20 and 0.52. Analysis of commanded and displayed haptic signals verifies that this system accurately overlays the modeled roughness and friction on the object's geometry, providing a significantly better match than the same models rendered using a Phantom Omni. [ABSTRACT FROM PUBLISHER]

Interacting with physical objects through a tool elicits tactile and kinesthetic sensations that comprise your haptic impression of the object. These cues, however, are largely missing from interactions with virtual objects, yielding an unrealistic user experience. This article evaluates the realism of virtual surfaces rendered using haptic models constructed from data recorded during interactions with real surfaces. The models include three components: surface friction, tapping transients, and texture vibrations. We render the virtual surfaces on a SensAble Phantom Omni haptic interface augmented with a Tactile Labs Haptuator for vibration output. We conducted a human-subject study to assess the realism of these virtual surfaces and the importance of the three model components. Following a perceptual discrepancy paradigm, subjects compared each of 15 real surfaces to a full rendering of the same surface plus versions missing each model component. The realism improvement achieved by including friction, tapping, or texture in the rendering was found to directly relate to the intensity of the surface's property in that domain (slipperiness, hardness, or roughness). A subsequent analysis of forces and vibrations measured during interactions with virtual surfaces indicated that the Omni's inherent mechanical properties corrupted the user's haptic experience, decreasing realism of the virtual surface. [ABSTRACT FROM PUBLISHER]

Purpose. Taking into account the traffic safety priority on the railway transport the search of factors promoting increase of derailment stability coefficient is an actual task. Purpose of the paper is the influence researches of the high-frequency vibrations on the train traffic safety parameter. In this case the special form of the wheel rim, at which its rigidity changes according to the harmonious law, was considered as a source of vibrations. Methodology. For the analysis of the vibration influence on the change of friction coefficient values the methods of so called vibrational mechanics were used. For determination of vibration amplitudes through moving the wheel flange points the finite-elements method was also used in the paper. Findings. During calculations it was established that the derailment stability coefficient to a great extent depends on the friction coefficient between wheel and rail. The paper shows that the friction coefficient in turn is influenced by the high-frequency vibrations. The form of the wheel rim was considered as a vibration source and the parameters characterizing vibration were calculated. It was given the quantitative estimation of the friction coefficient change under the vibration influence. It was also scientifically based the high-frequency vibration influence on the derailment stability coefficient. Originality. The paper proved the possibility of high-frequency vibration influence on the derailment stability coefficient. The studies theoretically substantiated the traffic safety increase in the presence of vibrations in the contact area of the wheel flange with the rail caused by special form of the wheel disc. Practical value. It is shown that the use of undulating wheel disc form do not constitute a threat to the traffic safety, and the availability of high-frequency vibration can reduce the derailment probability.

In this paper the high-frequency vibrations of beam structural elements on the example of cantilever rod are analyzed. The purpose of this article is to show the existence of the boundary frequency, above which the structure behaves as a system with a continuous spectrum, on elementary examples and to demonstrate the possibility of using this fact during engineering calculations performing.With the help of mathematical transformations and numerical experiments the existence of simple beam structures mixed spectrum, formed by the discrete and continuous parts, is shown. It is also shown that there is a boundary frequency that separates the portions of the spectrum and determines the upper frequency limit of the external effects, for which it is necessary to conduct dynamic account of structures. In this case the amplitude of the vibrations with a frequency exceeding the boundary one does not depend on the dynamic characteristics of the rod, but it is mostly determined by the static characteristics of the rod and the load.

The motion of Lagrange's top in the homogeneous gravity field is considered under the assumption that its suspension point accomplishes a specified high-frequency periodic motion with small amplitude (fast vibrations) in the three-dimensional space. The investigation is carried out in the framework of the approximate autonomous system of canonical equations of motion. Stationary rotations of Lagrange's top around its dynamical symmetry axis for a number of particular cases of the suspension point motions are found as positions of equilibriums of the reduced two-degree-of-freedom system. The linear and nonlinear analysis for their stability is carried out. The problems discussed in the report are new and have no analogues in domestic and foreign literature. [ABSTRACT FROM AUTHOR]

Various criteria of multiaxial fatigue fracture are studied for low-cycle fatigue (LCF); their generalizations are proposed for a very-high-cycle fatigue (VHCF) regime. The procedure of the stress state calculation is described for the compressor disk of the gas-turbine engine (GTE) in the flight cycle of loading and for the low-amplitude vibrations of the blades. The durability estimations of the disk operation are obtained for alternative mechanisms of LCF and VHCF using the calculated stress state and the models of multiaxial fatigue fracture. The results are compared with the data observed during operations. [ABSTRACT FROM AUTHOR]

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The study of a free-molecular flow through the membrane oscillating in its own plane has been conducted. Optimal values of membrane oscillation parameters for most efficient gas separation have been found. [ABSTRACT FROM AUTHOR]

Abstract: The influence of high-frequency vibrations of one of supporting rods on the axisymmetrical thermocapillary flow in the liquid half-zone and its linear stability respective to three-dimensional perturbations in the framework of generalized Boussinesq approximation was investigated numerically. The generation of mean vorticity in dynamical boundary layers is taken into account using effective boundary conditions. The influence of amplitude of vibrations and Prandtl number at different Weber number values is considered. Calculations were carried out using the finite differences method. It is shown, that vibrations can be used to control the flow, to reduce its intensity and to stabilize it. [Copyright &y& Elsevier]

Abstract: The spatiotemporal evolution of steady and oscillatory convective roll patterns in a plane horizontal layer subject to steady gravity and high-frequency vibrations is investigated numerically, considering a laterally periodic convective cell with rigid, impermeable horizontal boundaries. Simulations are performed for parameters adapted to laboratory experiments with an ethanol/water mixture with negative Soret coupling between temperature and concentration fields. The characteristics of the patterns are investigated in relation to heat intensity. Bifurcation diagrams are presented in the “Rayleigh number–Gershuni number” plane. [Copyright &y& Elsevier]

Consideration is given to a multilevel structural approach to the occurrence of local instability zones under the conditions of active deformation of a superconducting titanium alloy (Tc = 5.4 K). It is noted that the dislocation nanostructural level responsible for the energy activation in dislocation cores and determining the athermic and thermoactive deforming-stress and electrical-resistance jumps is a connecting link between all structural levels. [ABSTRACT FROM AUTHOR]

The effect of high-frequency vibrations of the field of external mass forces on convection in miscible fluids is considered for a system of convection equations obtained by an averaging technique. The structures of flows formed under initial conditions corresponding to physical experiments in microgravity are examined. [ABSTRACT FROM AUTHOR]

Stability of a plane-parallel flow of a nonuniformly heated binary mixture filling a vertical layer located in a field of gravity and in a high-frequency vibrational field is studied. The axis of vibrations is directed along the layer. The case of rigid and isothermal boundaries of the layer impermeable for the mixture is considered. The influence of thermal diffusion on the evolution of the admixture and the thresholds of flow stability is taken into account. The study is performed on the basis of equations for averaged fields. An asymptotic method with the use of the perturbation wavenumber as a small parameter is applied in the long-wave limit. For arbitrary values of the wavenumber, the limit of stability was determined by numerical integration. Charts of stability of gaseous and liquid binary mixtures are plotted. [ABSTRACT FROM AUTHOR]

Abstract: In piezoelectromagnetism, the three-dimensional fundamental equations well known in differential form are alternatively expressed in variational form through a unified variational principle. The variational principle is deduced from Hamilton’s principle by removing its constraints, the gradient equations and the constitutive relations, by use of Legendre’s transformation. Then, a hierarchical system of the two-dimensional approximate equations is systematically derived for the vibrations of a functionally graded piezoelectromagnetic plate. In the derivation, the unified variational principle and the power series expansions in the thickness coordinate for the field variables are used for the plate. The system of the plate equations in invariant, differential and fully variational forms is capable of studying the direct problems of all the types of vibrations of the plate at both low and high frequency. The uniqueness is investigated and the conditions sufficient for the uniqueness are enumerated in solutions of the system of the plate equations. Further, the variational principle and the system of the plate equations are shown to recover some of the earlier ones, as special cases. [Copyright &y& Elsevier]

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The presence of high-frequency velocity fluctuations in aneurysms have been confirmed by in-vivo measurements and by several numerical simulation studies. Only a few studies have located and recorded wall vibrations in in-vitro experiments using physiological patient models. In this study, we investigated the wall fluctuations produced by a flowing perfusion fluid in a true-to-scale elastic model of a cerebral fusiform aneurysm using a laser Doppler vibrometer (LDV). The model was obtained from patient data. The experimental setup reproduced physiologically relevant conditions using a compliant perfusion system, physiological flow parameters, unsteady flow and a non-Newtonian fluid. Three geometrically identical models with different wall elasticities were used for measurements. The influence of five different flow rates was considered. Wall vibrations were predominantly found at frequencies in the range 40-60 Hz and 255-265 Hz. Their amplitude increased with increasing elasticity of the model, but the spectral peaks remained at about the same frequency. Varying the flow rate produced almost no changes in the frequency domain of the models. The frequency of the spectral peaks varied slightly between points at the lateral wall and at the bottom of the aneurysm. Indeed, embedding the model in a fluid during measurements produced higher and smoother amplitude fluctuations.