Deflection Amplitude Research Articles

Seismic Detection of Oceanic Internal Gravity Waves From Subaerial Seismometers

AbstractOceanic internal gravity waves propagate along density stratification within the water column and are ubiquitous. They can propagate thousands of kilometers before breaking in shoaling bathymetry and the ensuing turbulent mixing affects coastal processes and climate feedbacks. Despite their importance, internal waves are intrinsically difficult to detect as they result in only minor amplitude deflection of the sea surface; the need for global detection and long time series of internal waves motivates a search for geophysical detection methods. The pressure coupling of a propagating internal wave with the sloping seafloor provides a potential mechanism to generate seismically observable signals. We use data from the South China Sea where exceptional oceanographic and satellite time series are available for comparison to identify internal wave signals in an onshore passive seismic data set for the first time. We analyze potential seismic signals on broadband seismometers in the context of corroborating oceanographic and satellite data available near Dongsha Atoll in May–June 2019 and find a promising correlation between transient seismic tilt signals and internal wave arrivals and collisions in oceanic and satellite data. It appears that we have successfully detected oceanic internal waves using a subaerial seismometer. This initial detection suggests that the onshore seismic detection and amplitude determination of oceanic internal waves is possible and can potentially be used to expand the historical record by capitalizing on existing island and coastal seismic stations.

Effect of Mooring Lines on the Hydroelastic Response of a Floating Flexible Plate Using the BIEM Approach

A boundary integral equation method (BIEM) model for the problem of surface wave interaction with a moored finite floating flexible plate is presented. The BIEM solution is obtained by employing the free surface Greens function and Green’s theorem, and the expressions for the plate deflection, reflection, and transmission coefficients are derived from the integro-differential equation. Furthermore, the shallow water approximation model and its solution is obtained based on the matching technique in a direct manner. The accuracy of the present BIEM code is checked by comparing the results of deflection amplitude, reflection, and transmission coefficients with existing published results and experimental datasets as well as the shallow water approximation model. The hydroelastic response of the moored floating flexible plate is studied by analyzing the effects of the mooring stiffness, incidence angle, and flexural rigidity on the deflection amplitude, plate deformations, reflection, and transmission coefficients. The present analysis may be helpful in understanding the different physical parameters to model a wave energy conversion device with mooring systems over BIEM formulations.

Lift Disturbance Cancellation with Rapid-Flap Actuation

Mitigation of vertical aerodynamic disturbances by means of a simple mechanical flap is investigated experimentally. A wall-to-wall NACA 0006 wing is bisected about the midchord for a 50%-chord flap length. Experiments are performed in a water tunnel at a chord-based Reynolds number of . The wing is driven in a sinusoidal vertical plunge motion as a spatially uniform, temporally varying surrogate to a vertical disturbance. Concurrently, the flap is actively deflected in a survey of kinematic parameters designed to suppress the influence of a plunge-induced disturbance. Plunge rates explored amount to disturbances incurred over a temporal range from one convective time to eight convective times. Two methodologies are employed to guide selection of flap deflection phase and amplitude necessary to preserve the baseline zero-lift state () of the undisturbed wing. In the first method, Theodorsen’s model is applied to arrive at an analytical solution to flap kinematics for a given prescribed plunge history. The theoretical derivation makes the standard assumptions of attached flow, planar wake, and no leading-edge vortical formations. Direct force measurements reveal reduction in lift transients by flap actuation of up to 87%, verifying the applicability of Theodorsen’s classical model. Further improvement is sought in a second method where empirical state-space modeling is formulated for lift cancellation. In this approach two separate lift models for wing plunge and flap deflection are constructed independently, and their superposition is employed to approximate the total lift in combined plunge and deflection motions. It is shown that although the empirical state-space approach performs similar to the inviscid theory of Theodorsen’s model, the empirical model proves more effective in suppressing the formation of the leading-edge vortex induced by plunge.

CFD-DEM study of mitigation of alternating spout deflection in a spout fluidized bed: A geometry perspective

Alternating spout deflection is a common instability problem in spout-fluidized beds. Geometrical modification to the reactor is a feasible way to mitigate the deflection. In this work, three kinds of geometrical designs are studied to mitigate the alternating spout deflection by the CFD-DEM approach. Design I is to add baffles at the top of two annulus regions. The results demonstrate that this design can significantly reduce the amplitude of spout deflection by reducing the stamping of falling particle flow on the annulus regions. Design II is to install two zigzag-like baffles in the fountain region, which is expected to disperse the particle distribution in the fountain region. However, this solution leads to non-alternating spout deflection, which is undesirable in the application. Design III is to modify the slot angle of the reactor bottom. The results show that 30° slot angle increases the frequency of the alternating spout deflection but rarely affects its amplitude. Non-alternating spout deflection occurs with 45° slot angle. This work benefits the hydrodynamics stability in spout fluidized beds.

Thermal noise in contact atomic force microscopy

As one of the fundamental sources of noise in atomic force microscopy (AFM), thermal fluctuations of the cantilever have been studied for the case of a free tip but not much for cantilevers in contact. In this paper, using the equipartition theorem, we calculated the thermal deflection amplitude for all normal modes of an elastically supported AFM cantilever, including the free cantilever as a special case. With increasing contact stiffness, the mean thermal fluctuation amplitude decreases for all cantilever modes when in the elastic contact. In addition, considering the optical lever detection scheme used in most AFMs, we calculated the corresponding output thermal noise amplitude. The experiments validated our theoretical calculations. Our investigation facilitates a more comprehensive understanding of the thermal noise in AFM. It provides guidance for thermally excited contact-resonance AFM, which is promising for quantitative viscoelastic measurements.

Propulsive properties of a flexible oscillating wing with time-varying camber deformation

In this article, a new conceptual design of flexible oscillating wing with time-varying camber deformation is introduced and the two-dimensional transient numerical simulation has also been conducted to compare the propulsive performance of current flexible oscillating wing with that of conventional rigid oscillating wing by using of the commercial software ANSYS Fluent 18.2 coupled with the dynamic mesh technique at moderate high Reynolds number of 1.0 × 106. In addition, the influence of the deflection amplitude, the deflection frequency as well as the deflection position along the chord length of the wing on the propulsive performance of current flexible oscillating wing have been analyzed. The numerical simulation results demonstrate that the introduction of flexible deformation motion does much good on improving the propulsive performance of oscillating wing and there exists optimum motion parameters leading to the highest propulsive efficiency. Compared with the conventional rigid oscillating wing, the existence of flexible deformation motion presents greater propulsive efficiency by largely increasing the thrust force within the whole period of motion and the maximum value of η can be increased by 28.3% compared with that of conventional rigid wing. Furthermore, the results also reveal that the optimum deflection motion should coincide with the rotation center of rigid motion and that conclusion provides much benefit for the future design of prototype manufacture.

Crack recovery and re-centring performance of cementitious composites with pseudoelastic shape memory alloy fibres

Newly developed hooked-end pseudoelastic shape memory alloy fibres (PSMAF) provide re-centring and crack-closing behaviour in cementitious composites. Relatively large PSMAF-reinforced specimens are tested under cyclic flexural loading at small and large deflection amplitudes to examine these capabilities realistically. Crack propagation, maximum crack width at each cycle, crack-closing ratio, and full-depth crack width are quantified through 2D digital image correlation (DIC) technique for composites with 0.5% to 1.25% PSMAF. The re-centring ratios are established for the developed composites, and their flexural performances are evaluated based on various parameters, including cyclic modulus, toughness, and ductility. Furthermore, X-ray micro-computed tomography and statistical analysis of spatial point patterns are employed to examine fibre dispersion in the cracked sections. Results indicate that PSMAF-reinforced composites with 0.75% and 1% fibre content exhibit considerable re-centring and crack-closing capabilities with minimal fibre clumping.

Dynamic Analysis of Lower Limb Exoskeleton Motion and Control Using Differential Transform Method

In this study, the nonlinear dynamic analysis of the motion and control of the lower limb exoskeleton using differential transform method is presented. Devices for medical processes are continuously undergoing improvement such as enhancing and assisting automatic therapies with flexible and configurable programs for treating people with partial disability in lower limbs as applied in lower-limb exoskeleton. The configurable programs in this exoskeleton can be applied to observe and control the motion of the exoskeleton for effective physiotherapy and reduced rehabilitation time for patients with such disability. Hence, a two degree of freedom nonlinear dynamic model for the motion and control of the lower limb exoskeletons was developed for two links. The nonlinear dynamic models are solved by applying the differential transform method (DTM) and verified with the forth order Runge-Kutta numerical method (RK4). The effects of the applied torque on the two links are investigated and it is observed that Link 1 has large negative deflection amplitude that drives link 2 towards the opposite positive direction. An increase in the applied torque resulted in increase in the amplitude of the system for all initial condition considered. This in turns increases the nonlinear dynamic behavior of link 2 due to its lower mass value. The speed of both links dampens out over the history due to the presence of damping term. At equilibrium, both links are in phase and have the same amplitude over the time history. This study provides an analytical tool for observing and controlling the motions of the lower limb exoskeleton and for improving the designs of the medical device.

Lateral buckling of subsea pipelines triggered by a sleeper with lateral constraint

In order to mitigate the maximum displacement and stress in the lateral buckling of subsea pipelines triggered by the sleeper, lateral constraint can be installed at the end of the sleeper to restrict the deflection of the buckled pipeline. In this study, the lateral buckling of subsea pipelines triggered by a sleeper with lateral constraint is analysed with considering the contact between the buckled pipeline and the lateral constraint. The mathematical model is validated through comparing the analytical solutions with finite-element results and test data. The influence of the sleeper length on the buckled configurations and post-buckling behaviour is investigated, focusing on the process after the buckled pipeline contacts with the lateral constraint. The amplitudes of deflection and stress along the buckled pipeline are compared to determine the maximum deflection and the maximum stress. A parametric analysis is carried out to show the effect of sleeper length on the amplitude of deflection, extrema of stress and the contact concentrated force between the pipeline and the lateral constraint. The results show that both the maximum deflection and maximum stress along the buckled pipeline become smaller compared to the case without lateral constraint after the buckled pipeline contacts with the lateral constraint.

Effect of Prostaglandin Analogues on Corneal Biomechanical Parameters Measured With a Dynamic Scheimpflug Analyzer.

Treatment with topical prostaglandin analogues (PGAs) induces increased corneal compliance in glaucoma eyes measured with a dynamic Scheimpflug analyzer. The purpose of this study was to evaluate the effect of topical PGAs on the corneal biomechanical properties. We retrospectively studied the biomechanical parameters of 31 eyes of 19 consecutive patients with glaucoma measured using a dynamic Scheimpflug analyzer (Corvis ST) before and after initiation of treatment with topical PGAs. No patients had a history of glaucoma treatment before the study and no other antiglaucoma medication was used during the study period. Nine biomechanical parameters were evaluated before and 61.6±28.5 days (range: 21 to 105 d) after initiation of the treatment. The changes in the corneal biomechanical parameters before and after treatment were analyzed using multivariable models adjusting for intraocular pressure and central corneal thickness. The Benjamini-Hochberg method was used to correct for multiple comparison. In multivariable models, PGA treatment resulted in shorter inward applanation time (P=0.016, coefficient=-0.151) and larger deflection amplitude (P=0.023, coefficient=0.055), peak distance (P=0.042, coefficient=0.131), and deformation amplitude ratio at 1 mm (P=0.018, coefficient=0.028). These associations consistently indicated increased corneal compliance (deformability) after PGA treatment. Topical PGAs resulted in greater corneal compliance, suggesting that the changes in the corneal biomechanical properties may lead to overestimation of the intraocular pressure-lowering effects.

Optomechanical Coupling Active Control for Improving Beam Pointing Accuracy of the Spatial Filter in PW Laser Facility

To improve the beam pointing accuracy of PW laser facility and reduce the optical axis deviation caused by the deflection amplitude response deviation of the confocal lens of spatial filter for microvibration action, an Optomechanical coupling vibration active control theory is proposed to make the peak value of output optical angle response lower than the pointing threshold value by 0.2 μrad. To establish an Optomechanical coupling vibration active control system, the active control parameters are introduced into the beam transmission matrix of the Optomechanical coupling system. The active control parameters and the peak value of the output light angle response are linked point to point. The algorithm flow of the active control system is designed, the control rules are established, and the control effect is verified. The results show that the peak value of the output optical angle response of the spatial filter decreases by 98.13%, and the attenuation is nearly two orders of magnitude after the active control, which effectively improves the convergence accuracy of the beam pointing of the spatial filter of the PW laser facility, and realizes the beam pointing control under the broadband excitation, and the control result is consistent with the expectation.

Capillary control of collapse in soft composite columns

Euler buckling is the elastic instability of a column subjected to longitudinal compression forces at its ends. The buckling instability occurs when the compressing load reaches a critical value and an infinitesimal fluctuation leads to a large amplitude deflection. Since Euler's original study, this process has been extensively studied in homogeneous, isotropic, linear-elastic solids. Here, we examine the nature of the buckling in inhomogeneous soft composite materials. In particular, we consider a soft host with liquid inclusions both large and small relative to the elastocapillarity length, which lead to softening and stiffening of a homogeneous composite respectively. However, by imposing a gradient of the inclusion volume fraction or by varying the inclusion size we can deliberately manipulate the spatial structure of the composite properties of a column and thereby control the nature of Euler buckling.

Effect of two-temperature parameter on thermoelastic vibration in micro and nano beam resonator

Thermoelastic vibration of micro and nano-beam resonators is described by the Euler-Bernoulli beam theory in context with two-temperature generalized thermoelasticity theory. The amplitude of deflection and thermal moment in the case of simply supported and the isothermal beam are obtained by the Laplace transform method along with the finite Fourier sine transform method and the vibration frequency is examined by the normal mode analysis when the beam-ends are clamped and isothermal. The effects of the two-temperature parameter and micro and nano-beam thickness on the amplitude of deflection, thermal moment, and thermoelastic vibration frequency of the micro and nano-beam resonator have been studied and shown with the numerical results. A comparison of the results with the corresponding results of the two-temperature generalized thermoelasticity (2TLS) and the Lord-Shulman (LS) theories is also presented. Besides, the size dependency nature of the micro and nano-beam is analyzed by analytical and numerical results.

Analysis of stability and bearing capacity of reinforced panels made of composite materials under shear

When performing stress verification analysis of wing spar supported composite walls it is essential to estimate local stability of smooth wall and general stability of orthotropic panel under shear forces. Almost square fragment of spar wall supported with ribs (between two ribs) is examined in this paper. In order to estimate general stability and load-bearing capacity of orthotropic panel geometrically nonlinear problem is examined. When examining linear problem compact expression for critical shear flow definition is explicitly written in order to estimate general stability with ultimate loading. When examining nonlinear problem a system of two equations in deflection amplitude is obtained. Besides nonlinear problem of smooth wall (skin) local stability and postbuckling state estimation with possible geometrically nonlinear behavior is examined. Analytical solution of orthotropic rectangular panel with shear geometrically nonlinear problem is obtained. Based on method of design by postbuckling state with critical shear stress provided with buckling a method of skin thickness definition is suggested. In order to apply obtained solutions to design activities method of orthotropic panels design by stability and postbuckling state with corresponding load level is shown.

Association Between Severity of Myopia and Deformation Characteristics of the Cornea Based on Propensity Score Matching Analysis.

To investigate the relationship between severity of myopia and corneal deformation characteristics after removing confounding factors using propensity score matching (PSM) analysis. A prospective study was conducted from April 1 to December 30, 2019 in Tianjin Eye Hospital. Participants were divided into low (spherical equivalent [SE] > -6.00 diopters) and high (SE ⩽ -6.00 diopters) myopia groups. Corneal deformation parameters were obtained using corneal visualization Scheimpflug technology. PSM analysis was conducted to minimize the effect of confounding factors (age, intraocular pressure, and corneal thickness) on corneal deformation. Correlation analysis and logistic regression models were applied to investigate the relationships between SE and corneal deformation parameters. A total of 2,126 eyes from 1,063 patients with a mean age of 23.81 ± 5.68 years were enrolled. The left and right eyes were analyzed separately. After PSM analysis, logistic regression indicated that the peak distance was a significant indicator for high myopia in both eye models (left: odds ratio [OR] = 1.978, 95% CI: 1.303 to 3.004; right: OR = 2.089, 95% CI: 1.362 to 3.202; P < .001). The maximum amplitudes of deformation and deflection and peak distance were significantly negatively correlated with SE in both eyes, whereas the whole eye movement was significantly positively correlated with SE (P < .01), as well as the deformation amplitude at the second applanation (P < .001). Eyes with high myopia exhibited larger deformation and deflection amplitude compared to eyes with low myopia. The high distance between bending points of the cornea at the highest concavity (peak distance) may be a feature of high myopia. [J Refract Surg. 2021;37(5):344-350.].

Compressed stiffened composite panels design with skin postbuckling behavior

The aim of this paper is development of stiffened composite panels design method taking thin skin postbuckling behavior and stringers elastic behavior in case of longitudinal compression into account. Statement of the problem takes geometrically non-linear correlations into account. Variant of rigid boundary conditions is considered for both stiffened panels and skin. Analytic solution of non-linear problem using Ritz method which is reduced to solution of non-linear system of two equations in skin and stringer deflection amplitudes is shown. Obtained analytical solution is used for development of load-bearing panels design method based on postbuckling state. A design method based on thin skin postbuckling state not taking stringers influence into account is shown as an example. In this case following variants of strength criteria are considered: reaching longitudinal normal or tangential transverse critical stress. Besides stiffened composite panels design method taking skin postbuckling behavior in case of stringers elastic behavior into account is shown. With known stringer parameters design task is reduced to solution of non-linear system of two equations in skin thickness and stringer deflection amplitude. In this case stipulation of reaching critical normal stress in the skin is taken as strength criterion.

Experimental investigation of buckling of dented cylindrical shells under axial compression

The results of unique experimental studies of buckling of dented axially compressed unstiffened cylindrical shells are provided in the suggested paper. The dimple-like geometrical imperfections of different shape, size, deflection amplitude, and number of dents were created on cylindrical shells before axial loading. The initial deflection amplitude varied in the wide range, up to several shell thicknesses. In all cases the plateaus were discovered on the buckling load initial deflection diagrams. Corresponding axial loads were close to local lower buckling loads of perfect shells. These loads are defined as minimum values of axial force when the post-buckling equilibrium states of the perfect structure with one or several dimples exist. It was shown that the lower local buckling loads slightly depend on geometrical imperfections and therefore can be used for estimation of design buckling load of the structure. Over 50 specimens were tested. Pre-buckling and post-buckling behavior of imperfect shells was studied.

Influence of corneal shape parameters on corneal deformation responses measured with a Scheimpflug camera.

To investigate the effect of corneal shape parameters on corneal deformation responses measured with a Scheimpflug camera. A total of 241 eyes of 241 participants were enrolled in this study. The anterior and posterior corneal curvature radii (CCR), anterior and posterior corneal Q-values, and corneal diameters of the participants were measured using the Pentacam HR. A total of 17 corneal deformation parameters including time, velocity, deflection amplitude, length, and area during ingoing applanation, highest concavity, and outgoing applanation were recorded by corneal visualization using Scheimpflug technology (Corvis ST). The effect of corneal shape parameters on corneal deformation responses was evaluated using multivariate regression models. Multivariate regression analyses showed that six, five, four, and three corneal deformation parameters were significantly correlated with anterior CCR, posterior CCR, anterior Q-value, and posterior Q-value, respectively. Steeper anterior corneal curvature was associated with faster velocity during ingoing applanation and greater deformation during outgoing applanation. Steeper posterior corneal curvature was correlated with faster velocity during outgoing applanation and greater deformation during ingoing applanation. Eyes that had steeper corneal curvatures were associated with less stiff corneas. More negative anterior Q-value corresponded with faster velocity and greater deformation during ingoing applanation. Eyes that had more prolate posterior corneal surfaces showed more resistance to corneal deformation at the highest concavity. However, corneal diameter was not selected in any corneal deformation parameters models. Corneal deformation response is significantly influenced by anterior and posterior corneal curvature and corneal asphericity, but not corneal diameter.

Functional and morphological comparison of extracellular matrices derived from porcine small intestinal submucosa and porcine dermis to support rabbit uterus regeneration.

he aim of this study was to compare the ability of extracellular matrices (ECMs) of various structural origins to support uterus regeneration and maintain contractile function. The experiment was carried out in 18 New Zealand white female rabbits divided into a control group and two experimental groups. In the control group, bipolar electrodes were attached to the uterine horns to collect electromyography data. In the experimental groups, uterine horns were partially excised with immediate implantation of the extracellular matrix (ECM) derived from porcine small intestinal submucosa (SIS), DynaMatrix®, or from porcine dermis, Medeor® Matrix. Twelve weeks later, bipolar electrodes were attached to the regeneration areas in both experimental groups. The electromyography data in all groups were continuously recorded after administration of a single dose of estradiol valerate. Fourteen weeks after EMCs implantation, the rabbits were spayed, and the uterine wall was sampled for histological and immunohistochemical evaluation. The regenerated uterus retained the myoelectric activity pattern, and the mean amplitudes of maximum deflections did not differ between the experimental and control groups. The regeneration supported by the SIS-derived ECM was more advanced than that supported by the dermal-derived ECM. However, some pathological changes were noted in both experimental groups within the regeneration areas.

Optimized Fuzzy Skyhook Control for Semi-Active Vehicle Suspension with New Inverse Model of Magnetorheological Fluid Damper

To improve the performance of vehicle suspension, this paper proposes a semi-active vehicle suspension with a magnetorheological fluid (MRF) damper. We designed an optimized fuzzy skyhook controller with grey wolf optimizer (GWO) algorithm base on a new neuro-inverse model of the MRF damper. Because the inverse model of the MRF damper is difficult to establish directly, the Elman neural network was applied. The novelty of this study is the application of the new inverse model for semi-active vibration control and optimization of the semi-active suspension control method. The calculation results showed that the new inverse model can accurately calculate the required control current. The fuzzy skyhook control method optimized by the grey wolf optimizer (GWO) algorithm was established based on the inverse model to control the suspension vibration. The simulation results showed that the optimized fuzzy skyhook control method can simultaneously reduce the amplitude of vertical acceleration, suspension deflection, and tire dynamic load.