Zero Displacement Research Articles

Mathematical Modelling of a Single Magneto-Rheological for Car Suspension System Using Modified Bouc-Wen Model

Magneto-Rheological (MR) automotive suspension represents the most advanced technology currently available for enhancing passenger comfort through intelligent fluid behaviour. This work employed a Modified Bouc-Wen model to create a mathematical representation of a single MR vehicle suspension and compared its ride performance to that of passive suspension systems. The model was formulated and solved using second-order linear differential equations, with MATLAB software utilized to visualize the results. The maximum vertical displacement for the single MR mathematical model in this work was 0.031 m, while the minimum was -0.0124 m. At the minimum position, the vertical displacements for the passive model were 0.0532 m and -0.0133 m. The results demonstrated that the vertical displacement variation was similar for both the mathematical model and the passive system. All displacements obtained from the mathematical modeling of the single MR system were close to its mean of 0.000875 m (nearly zero). There was reduced vibration when zero displacement was achieved. It was concluded that MR damper significantly improved car suspension performance compared to passive solutions. This paper developed a single MR vehicle suspension system using the Modified Bouc-Wen model in a Proton Preve.

Reconstructing the source condition for focused shear wave beams in soft elastic media

Shear waves are employed in medical ultrasound imaging because they reveal variations in viscoelastic properties of soft tissue. Focused shear waves produced by a longitudinally vibrating piston at several hundred hertz are investigated here experimentally in soft tissue phantoms and using an analytical model for shear wave beam generation and propagation. Experiments employed a spherically concave piston shaped to focus the shear wave beam at a depth of 4 cm in a soft tissue phantom. Analytical modeling of this data provided a good fit, but required treating the focal length and piston diameter as adjustable parameters. The largest source of error in the modeling is suspected to be that the source condition is assumed to exhibit zero displacement surrounding the piston, whereas the actual condition in the source plane is a traction-free surface surrounding the piston. Here, in order to elucidate the actual source condition, numerical back propagation of field measurements is employed. Simulations show that the shear source condition can be accurately recovered with information related only to the shear wave, i.e., without compressional wave information. Back propagation of measured beams is discussed in the context of more accurately modeling the source condition for future device optimization.

Zero displacement cost model: a simplified RM model for post-COVID-19 O&D management

In the airline industry, the aim of O&D RM is to optimize network revenue by increasing seat availability for high-revenue connecting passengers while preventing connecting passengers from displacing high-yield local passengers to reduce displacement costs. Traditional O&D models rely heavily on complex historical data analysis. The outbreak of COVID-19 has led to an unprecedented disruption of the global airline industry. It has reset historical data, thereby reducing the reliability of the traditional forecasting and optimization results. This paper proposes Zero Displacement Cost (0DC) model as a simplified and flexible model for airlines to manage O&D in the post-COVID-19 world.

Multiplicative suppression of decoherence.

Combining different protocols extends the life of a quantum system

Design and implementation of net zero displacement filter for the synthesis of a mechanical shock signal under specified shock response spectrum

Electronic and optical products are vulnerable under mechanical shock environment. Designed products need to be validated by shock testing and/or numerical simulation, using representative acceleration-time history signals. However, specifications derived from measurements are normally given in terms of shock response spectrum (SRS) without a corresponding time history signal, and therefore, there is a need to synthesis acceleration-time histories from a given SRS specification. This paper proposed a net zero displacement filter and a realistic time history synthesis method. By scaling a relevant field measurement, acceleration-time histories can be synthesized, which can meet the net zero displacement constrain and a given SRS specification within ±3 dB margin.

Deformation characteristics and mechanism of deep subsize coal pillar of the tilted stratum

AbstractBased on the analysis of the monitoring data of surface displacement and internal multipoint displacement of coal pillars near three inclined strata roadways, which have similar burial depth and different surrounding rock conditions in a coal mine in the east China, the coal pillars’ stress change was combined with discontinuous numerical simulation software to simulate the deformation process of one of the roadways. Field monitoring data and numerical simulation results show that when this working face roadway is dug, the coal pillar enters plastic state after being affected by multiple mining influence, but it can still maintain the basic stability of the roadway and control coal pillar deformation under the current widely used supporting method. With the shortening of the distance between the monitoring area and the working face, the vertical and horizontal stress in the coal pillar increase gradually, but the maximum value of the vertical stress decreases by 1.4 MPa, and deformation amount and velocity of the coal pillar show the characteristics of nonlinear rapid increase. The shape of the vertical stress core area in the coal pillar changed from oval to rectangle, and the width of the core area increased, and it moved 1 m to the goaf side. In the process of coal pillar deformation, there is no zero displacement surface within the monitoring range of 6 m.

A galloping energy harvester with flow attachment

Aeroelastic energy harvesters are a promising technology for powering wireless sensors and microelectromechanical systems. In this letter, we present a harvester inspired by the trembling of aspen leaves in barely noticeable winds. The galloping energy harvester, a curved blade oriented perpendicular to the flow, is capable of producing self-sustained oscillations at uncharacteristically low wind speeds. The dynamics of the harvesting system are studied experimentally and compared to a lumped parameter model. Numerical simulations quantitatively describe the experimentally observed dynamic behaviour. Flow visualisation is performed to investigate the patterns generated by the device. Dissimilar to many other galloping harvester designs, the flow is found to be attached at the rear surface of the blade when the blade is close to its zero displacement position, hence acting more closely to aerofoils rather than to conventionally used bluff bodies. Simulations of the device combined with a piezoelectric harvesting mechanism predict higher power output than that of a device with the square prism.

Defect-interface interactions in irradiated Cu/Ag nanocomposites

In this work, we employ transmission electron microscopy and helium ion irradiation to study the response of biphase interfaces to radiation induced point defect fluxes from the two adjoining phases. Analysis of interface-affected defect accumulation was carried out over a wide range of radiation damage levels from near zero displacement per atom (dpa) to 16 dpa and helium concentrations of 0 at.% to 8 at.%. Results show a strong interface density dependence in which Cu/Ag interfaces in the nanolayered regions spaced <500 nm were remarkably microstructural stable over the entire range without accumulating micro-scale defects, while those spaced >1 μm apart were destroyed. We report the concomitant development of a bubble-free zone in Cu that was independent of defect levels and interface-contacting bubbles zone in Ag. This finding is explained by bias segregation to the interface of interstitials from Ag and vacancies to misfit dislocation nodes in the interface from Cu. The point defect transfer across the interface can be explained by the spatial variation in interface pressure within the interface and gradient in pressure across the interface, both originating from the lattice mismatch and surface energy difference between the two crystals.

Estimation of foot trajectory during human walking by a wearable inertial measurement unit mounted to the foot

To establish a supportive technology for reducing the risk of falling in older people, it is essential to clarify gait characteristics in elderly individuals that are possibly linked to the risk of falling during actual daily activities. In this study, we developed a system to monitor human gait in an outdoor environment using an inertial measurement unit consisting of a tri-axial accelerometer and tri-axial gyroscope. Step-by-step foot trajectories were estimated from the sensor unit attached to the dorsum of the foot. Specifically, stride length and foot clearance were calculated by integrating the gravity-compensated translational acceleration over time during the swing phase. Zero vertical velocity and displacement corrections were applied to obtain the final trajectory, assuming the slope of the walking surface is negligible. Short, normal, and long stride-length walking of 10 healthy participants was simultaneously measured using the proposed system and a conventional motion capture system to evaluate the accuracy of the estimated foot trajectory. Mean accuracy and precision were approximately 20±50mm, for stride length, and 2±7mm for foot clearance, indicating that the swing phase trajectory of the sensor unit attached to the foot was reconstructed more accurately and precisely using the proposed system than with previously published methods owing to the flat floor assumption. Although some methodological limitations certainly apply, this system will serve as a useful tool to monitor human walking during daily activities.

Adjustable Linkage Pump: Efficiency Modeling and Experimental Validation

Variable displacement pumps are a key component to a variety of mobile and industrial hydraulic systems, yet the efficiency of existing pump architectures is poor at low displacement. As a solution to this issue, a new pump architecture is proposed that eliminates the planar hydrodynamic joints of a conventional architecture with rolling-element pin joints in an adjustable linkage. This new architecture uses an adjustable six-bar linkage that reaches true zero displacement and has the same top-dead-center (TDC) position regardless of displacement. In this work, the linkage kinematics and dynamics are discussed, an energy loss model is developed and used to drive design decisions of a first generation prototype, and experimental results are presented to validate the model. It is shown that this linkage-based, variable, positive displacement architecture shows promise as a highly efficient alternative to existing pump architectures across a wide range of displacements.

Vibration reduction at desired locations on a beam by creating nodes using tunable vibration neutralizers

Vibration neutralizers provide an effective method of attenuating tonal vibrations within a structure. In this paper, variable stiffness vibration neutralizers are used to impose zero displacement or nodes to reduce vibration at desired locations on a Euler-Bernoulli beam subjected to forced harmonic excitation. An iterative procedure is developed to find the required resonance frequencies of neutralizers to create nodes at selected locations. Numerical tests are performed to show the viability of the procedure that is developed. Experimental tests are conducted and results are compared with those obtained by numerical tests.

Design and Testing of an Adjustable Linkage for a Variable Displacement Pump

A variable displacement hydraulic pump/motor with high efficiency at all operating conditions, including low displacement, is beneficial to multiple applications. Two major energy loss terms in conventional pumps are the friction and lubrication leakage in the kinematic joints. This paper presents the synthesis, analysis, and experimental validation of a variable displacement sixbar crank-rocker-slider mechanism that uses low friction pin joints instead of planar joints as seen in conventional variable pump/motor architectures. The novel linkage reaches true zero displacement with a constant top dead center position, further minimizing compressibility energy losses. The synthesis technique develops the range of motion for the base fourbar crank-rocker and creates a method of synthesizing the output slider dyad. It is shown that the mechanism can be optimized for minimum footprint and maximum stroke with a minimum base fourbar transmission angle of 30 deg and a resultant slider transmission angle of 52 deg. The synthesized linkage has a dimensionless stroke of 2.1 crank lengths with a variable timing ratio and velocity and acceleration profiles in the same order of magnitude as a comparable crank-slider mechanism. The kinematic and kinetic results from an experimental prototype linkage agree well with the model predictions.

The Use of Normalized Cross-Correlation Analysis for Automatic Tendon Excursion Measurement in Dynamic Ultrasound Imaging

The work describes an automated method of tracking dynamic ultrasound images using a normalized cross-correlation algorithm, applied to the patellar and gastrocnemius tendon. Displacement was examined during active and passive tendon excursions using B-mode ultrasonography. In the passive test where two regions of interest (2-ROI) were tracked, the automated tracking algorithm showed insignificant deviations from relative zero displacement for the knee (0.01 ± 0.04 mm) and ankle (-0.02 ± 0.04 mm) (P > .05). Similarly, when tracking 1-ROI the passive tests showed no significant differences (P > .05) between automatic and manual methods, 7.50 ± 0.60 vs 7.66 ± 0.63 mm for the patellar and 11.28 ± 1.36 vs 11.17 ± 1.35 mm for the gastrocnemius tests. The active tests gave no significant differences (P > .05) between automatic and manual methods with differences of 0.29 ± 0.04 mm for the patellar and 0.26 ± 0.01 mm for the gastrocnemius. This study showed that automatic tracking of in vivo displacement of tendon during dynamic excursion under load is possible and valid when compared with the standardized method. This approach will save time during analysis and enable discrete areas of the tendon to be examined.

Drained cavity expansions in soils of finite radial extent subjected to two boundary conditions

SUMMARYThe problem of drained cavity expansion in soils of finite radial extent is investigated. Cylindrical and spherical cavities expanded from zero radius subjected to either constant stress or zero displacement at the finite boundary are considered. The generalised analytical solution procedure presented enables more advanced constitutive models to be implemented than have been possible in previous studies. Results generated for Sydney quartz sand highlight substantial differences between cavity limit pressures for the two boundary conditions and for boundaries of finite and infinite radial extent. This is of significance in accounting for boundary effects when interpreting cone penetration tests conducted in calibration chambers. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Perturbation theory and the Rayleigh quotient

The characteristic frequencies ω of the vibrations of an elastic solid subject to boundary conditions of either zero displacement or zero traction are given by the Rayleigh quotient expressed in terms of the corresponding exact eigenfunctions. In problems that can be analytically expanded in a small parameter ε, it is shown that when an approximate eigenfunction is known with an error O(εN), the Rayleigh quotient gives the frequency with an error O(ε2N), a gain of N orders. This result generalizes a well-known theorem for N=1. A non-trivial example is presented for N=4, whereby knowledge of the 3rd-order eigenfunction (error being 4th order) gives the eigenvalue with an error that is 8th order; the 6th-order term thus determined provides an unambiguous derivation of the shear coefficient in Timoshenko beam theory.

Fixture control by hydraulic actuation using a reduced workpiece model

In this paper the dynamic behaviour of a part and an actuated fixture system is studied. The part is modelled using the finite element method. Subsequently, a reduced model is established using the Craig—Bampton reduction method in order to create a small-sized model, accurately describing the dynamic behaviour of the part. The clampers and locators of the fixture are modelled as springs. The fixture frame is considered to be much stiffer than the locators such that it provides the zero displacement boundary conditions to the locators. A hydraulic actuator is utilized to provide the adaptive clamping forces. A methodology is presented to obtain the reduced model of the part and to couple it with the model of the active fixture. After investigating proportional control, lag, and lead filters for dynamic compensation, the analysis shows that position feedback can be used effectively to minimize unnecessary displacement of the workpiece.

Der Beitrag neuer MRT-Untersuchungs- und Analysetechniken

Routine MRI is a key element in the diagnosis and differential diagnosis of MS. Conventional MRI contrasts are very commonly used as adjuncts to the clinical and neurophysiological assessment of the patient status in the course of the disease. Background information from MRI frequently offers the best opportunity to provide an individual understanding and concept of the patients disease and provides a basis for a treatment rationale. Beyond the visualisation of the groß pathology on brain MRI imaging of the spinal cord is acknowledged as an area of great importance, however it is technically challenging and therefore its use is more limited. New technical opportunities allow the fast visualisation of the whole cord. We have employed a fast biplanar MRI approach of the whole cord as a routine examination, which can be very helpful to ascertain cord pathology. Another area where MRI can be useful is the detection and quantification of tissue changes that are not easily accessible to the eye. Subtle changes are known to occur in the NAWM of MS patients, including diffuse astrocytic hyperplasia, patchy edema, perivascular infiltration, gliosis, abnormally thin myelin and axonal loss. It is also evident from pathological studies that frequently a slowly progressive axonal loss leeds to brain atrophy. Atrophy assessment becomes increasingly more sophisticated and new quantitative MRI techniques (Q-space diffusion imaging) may open new avenues to also assess the less overt pathological changes in MS. We have recently used Q-space imaging that demonstrates a high sensitivity to detect reductions of the slow diffusion component in the NAWM of patients with different MS types. Color coding of resulting calculated maps of the „Probability of Zero Displacement“ (PZD) show areas of loss of the slow diffusion component quite obviously making it also accessible to a qualitative analysis approach. Such additional information maybe of value for the clinician when the clinical status of the patient is still functionally well compensated in a low EDSS range but more objective information on morphological changes are useful.

On the solvability of a variational problem about phase transitions in continuum mechanics

We study a variational problem about phase transitions in continuum mechanics under the condition that the surface tension coefficient vanishes. A homogeneous isotropic two-phase elastic medium occupies a ball-shaped domain, the zero displacement field is fixed on the boundary of this domain, and a spherically symmetric force field acts on the medium. The solvability of this problem is established. As is shown, if a force field is nonzero almost everywhere, then the problem has only spherically symmetric solutions. Bibliography: 9 titles.

THE CROSSING FREQUENCY AS A MEASURE OF HEAT EXCHANGER SUPPORT-PLATE EFFECTIVENESS

The crossing frequency is the number of times per second the vibration amplitude crosses the zero displacement line from negative displacement to positive displacement. In flow-induced vibration in which the motions are often random and/or a number of modes contribute to the vibration amplitudes, the crossing frequencies are modal-weighted average frequencies of the vibration. It is postulated in this paper that the crossing frequency can be used as a measure of heat exchanger support-plate effectiveness. Using a time-domain, nonlinear analysis technique, the crossing frequencies of a tube vibrating in support plates with oversized holes can be computed as a function of time and the tube-to-support-plate clearances. It was found that the fluid–elastic stability margin of a tube bundle, in the context of the original Connors' equation for tube bundle fluid–elastic instability, should be independent of the tube-to-support-plate clearances. A simple method of estimating the critical velocity based on the time-domain equation of fluid–elastic stability is suggested.

Crystal Structure of Pb5Bi18P4O42: A Fluorite-Related Superstructure

Single crystals of a new oxyphosphate of bismuth and lead, Pb5Bi18P4O42, were studied using short-wavelength synchrotron X-ray radiation. The compound is monoclinic, I2/m, a=11.885(2) Å, b=11.540(2) Å, c=15.636(3) Å, β=90.23(3)°, Z=2. The crystal is twinned by pseudo-merohedry. The structure refinement converged to R=0.0366. There are five crystallographically independent Bi atoms. The oxygen coordination polyhedron around Bi(1) is a slightly distorted cube with Bi–O bonds varying from 2.381(11) to 2.662(10) Å. The other four Bi atoms are in a severely distorted oxygen environment with bond lengths varying from 2.102(5) to 3.16(2) Å. A greater variation of the oxygen coordination polyhedra exists around the three crystallographically independent Pb atoms changing from a somewhat elongated cube to a monocapped pentagonal bipyramid; bond distances vary from 2.13(2) to 3.38(2) Å. Of 20 crystallographically independent oxygen ions 11 are disordered. The structure consists of two Bi–O layers parallel to (101). They are interconnected perpendicular to [010] by layers consisting of Pb and PO4. The two crystallographically independent PO4 moieties are disordered. This compound displays a δ-Bi2O3 fluorite superstructure. The locations of the nonbonded lone-pair electrons were calculated and vary from 0 to 1.1 Å. These displacements from the cation nucleus are indicative of the extent of s–p hybridization, where zero displacement represents the spherical nonbonded 6s2 orbital. The extent of hybridization is a function of the distortion of the oxygen coordination polyhedron around the cation.