Deflection Amplitude Research Articles

Dynamics of viscoelastic material sandwich beam

ABSTRACT In this study, the non-linear dynamics of a horizontal motioned hub-beam system with passive constrained layer damping treatment are presented. The beam is constructed with three layers, viz., the host layer and the constrained layer with isotropic material, and the core layer of viscoelastic material. The system is non-linear due to coupling between the rigid motion of hub and flexible motion of the beam and also due to consideration of the beam curvature effect of bending. The equations of motion are derived using Hamilton’s principle based on expressing the kinetic energy and potential energy of the manipulator system in terms of generalised coordinates. The problem is approached by the finite element method, and the Newmark’s beta time integration scheme is adopted. Numerical simulations show that the viscoelastic material not only reduces the amplitude of elastic deflection but also quickly attenuates the vibration to zero. The results are evaluated for different values of thickness of the constrained layer, viscoelastic layer, payloads, and elastic modulus of each layers. It is observed that the vibration amplitude could be controlled through the use of the passive layer of damping.

A stochastic approach to estimate intraocular pressure and dynamic corneal responses of the cornea

IntraOcular Pressure (IOP) is one of the most informative factors for monitoring the eye-health. This is usually measured by tonometers. However, the outputs of the tonometers depend on the physical and geometrical properties of the cornea. Therefore, the common practice is to develop a numerical model to generate some correction factors. The main challenge here is the accuracy and efficiency of a numerical model in predicting the IOP and Dynamic Corneal Response (DCR) of each patient. This study addresses this issue by developing a two-step surrogate model based on adaptive sparse Polynomial Chaos Expansion (PCE) for fast and accurate prediction of the IOP. In this regard, first, an FE model of the cornea has been developed to predict the DCR parameters. This FE model has been replaced with a PCE-based surrogate model to speed up the simulation step. The uncertainties in the geometry and material model of the cornea have been propagated through the surrogate model to estimate the distributions of the DCR parameters. In the second step, the combination of DCR parameters and the input parameters provide a proper parameter space for developing an efficient data-driven PCE model to predict the IOP. Moreover, sensitivity analysis by using PCE-based Sobol indices has been performed. The results demonstrate the accuracy and efficiency of the proposed method in predicting the IOP. Sensitivity analysis revealed that IOP measurement was influenced mostly by deflection amplitude and applanation time. The analysis indicates the importance of the interactions between the parameters.

Nonlinear Vibration of Nanocomposite Multilayer Perovskite Solar Cell in Thermal Environment

In this work we investigated the nonlinear vibration of nanocomposite multilayer perovskite solar cell (NMPSC) subjected to the combination of mechanical and thermal loadings. The model of organic solar cell is assumed to consist seven functional layers: Au, Spiro-OMeTAD, PEDOT:PSS, Graphene oxide, MAPbI3, TiO­2 and IOT, and glass substrate. The governing equations are established basing on the classical plate theory taking into account the effect of elastic foundations and initial imperfection. Four edges of the NMPSC are assumed to be supported immovably in a transverse plane. The relationship between deflection amplitude and time as well as the expression of natural frequency of NMPSC are obtained by using the Galerkin and Runge – Kutta methods. The numerical results showed that the nonlinear dynamic response and the natural frequency of NMPSC have been strongly influenced by the geometrical and material parameters, initial imperfection, temperature increment and elastic foundations. 
 Keywords: Perovskite solar cell; nonlinear vibration; elastic foundations; initial imperfection; thermal environment

Scattering of Water Waves by Very Large Floating Structure in the Presence of a Porous Box

Abstract We investigate the effectiveness of a porous box in attenuating the structural response of a very large floating structure (VLFS). Assuming the water depth to be finite and small amplitude water wave theory, the physical problem is formulated by employing Darcy’s law for flow past a porous structure. The boundary value problem is reduced to a system of linear algebraic equations with the aid of matched eigenfunction expansion method. Further, these simultaneous equations are solved numerically to compute physical quantities. The mathematical model is validated through a comparison with the theoretical results available in the literature. The reflection, transmission, and dissipation coefficients, elastic plate deflection, forces acting on the box, and free-surface elevation are computed. The reflection, transmission, and dissipation coefficients exhibit an oscillatory pattern for large values of wavenumber irrespective of the structural parameters of the box. It is highlighted that a porous box with moderate values of the porous-effect parameter is effective in reducing strain and shear force on the VLFS. Further, the results on elevation and VLFS deflection depict that the suitable porous-effect parameter values for the box reduce the resultant wave amplitude of the elastic plate deflection as well as the amplitude in the lee side of the VLFS. The study reveals that the width and height of the porous box are critical toward the trapping of incident waves inside the box and dissipating the maximum amount of incident wave energy in reduction of wave transmission in the lee side of the structure and thereby attenuating the structural response of the VLFS.

Static buckling analysis and geometrical optimization of magneto-electro-elastic sandwich plate with auxetic honeycomb core

The nonlinear static buckling analysis of magneto-electro-elastic sandwich plate on Pasternak-type elastic foundations subjected to the mechanical, thermal, electric and magnetic loadings is presented in this paper. The sandwich plate is composed of an auxetic honeycomb core with negative Poisson’s ratio and two face sheets made of magneto-electro-elastic​ material. The system basic equations are derived based on the Reddy’s higher order shear deformation plate theory taking into account the effect of von Kármán the kinematic nonlinearity and initial imperfection. The form of possible solutions and electric, magnetic potentials are chosen as trigonometric functions based on two cases of boundary conditions. The relationship between axial compressive loading and dimensionless deflection amplitude is determined by using the Galerkin method. For optimization problem, the Bees algorithm is applied to obtain the maximum value of critical buckling load of the sandwich plate which depends on five geometrical and material parameters. The effects of elastic foundations, temperature increment, geometrical parameters and electric and magnetic potentials on the stability characteristics are investigated in numerical results. The accuracy and reliability of present approach is confirmed by comparisons with the existing results in the literature.

Numerically simulated influence of positive ions on the propagation of a positive streamer initiated in an argon plasma jet

A plasma jet with inert working gas operates in a streamer discharge mechanism. The propagation behavior of streamers determines the distribution of active species, which play a key role in the applications of plasma jets. To make clear streamer behavior under the influence of residual positive ions, a two-dimensional fluid model based on the continuity, the conservation, and Poisson's equations is employed to numerically investigate the dynamic behavior of a positive streamer when it approaches a cloud of positive ions with different densities and scales. Results indicate that the streamer always propagates along the axis and passes through the cloud of positive ions if the ions are rarefied (1.0 × 1016 m−3 in the core), which behaves like a free streamer. If the ion cloud has a medium density (5.0 × 1016 m−3 in the core), the streamer first deflects upward when it approaches the vicinity of the ion cloud and then deflects downward when it departs from the ion cloud, leaving a detouring track. The detouring track is also left if the ions are fairly dense (1.0 × 1017 m−3 in the core). However, the detouring process is fulfilled by the relay of two streamers, which are initiated at the jet nozzle and inside the ion cloud, respectively. Moreover, the velocity of the streamer is simulated with varying ion densities, voltage amplitudes, and gap widths. In addition, the deflection amplitude of the detouring track is investigated as a function of the voltage amplitude, gap width, ion density, cloud position, and cloud scale.

Corneal Biomechanics for Ocular Hypertension, Primary Open-Angle Glaucoma, and Amyloidotic Glaucoma: A Comparative Study by Corvis ST.

BackgroundTo evaluate biomechanical parameters of the cornea provided by Corvis ST in patients with ocular hypertension, primary open-angle glaucoma, and amyloidotic glaucoma and to compare with healthy controls.MethodsThis was a cross-sectional study of patients with ocular hypertension, primary open-angle glaucoma, and amyloidotic glaucoma that underwent Corvis ST imaging. Primary outcome was the comparison of corneal biomechanical parameters between study groups after adjusting for age, gender, Goldmann intraocular pressure (GAT-IOP), and prostaglandin analogues medication. Secondary outcome was the comparison of different IOP measurements in each group.ResultsOne hundred and eighty-three eyes from 115 patients were included: 61 with primary open-angle glaucoma, 32 with amyloidotic glaucoma, 37 with ocular hypertension and 53 were healthy controls. Amyloidotic glaucoma group had smaller radius (p=0.025), lower deflection amplitude at highest concavity (p=0.019), and higher integrated radius (p=0.014) than controls. Ocular hypertension group had higher stiffness parameter at first applanation (p=0.043) than those with primary open-angle glaucoma, and higher stress–strain index (p=0.049) than those with amyloidotic glaucoma. Biomechanically corrected intraocular pressure was significantly lower than Goldmann intraocular pressure in group with primary open-angle glaucoma (p=0.005) and control group (p=0.013), and Goldmann intraocular pressure adjusted for pachymetry in group with primary open-angle glaucoma (p=0.01).ConclusionEyes with amyloidotic glaucoma have more deformable corneas, while eyes with ocular hypertension have less deformable corneas. These findings may be linked to the susceptibility to glaucomatous damage and progression. There were significant differences between Goldmann applanation tonometry and biomechanically corrected intraocular ocular pressure provided by Corvis ST.

Fresh Water Aquatic Training in Patients with Upright Posture Maintaining Disorders

The use of the fresh water aquatic training course, as a more gentle training method, may allow patients to ensure effective restoration of muscle functions responsible for maintaining an upright body position. A more accurate control of the course results can be performed using a virtual analysis carried out using the «Habilect» system that allows to determine the body parts attitude. Aim. To study the effect of training in fresh water using the Habilect system based on the Microsoft Kinect infrared sensor (video stabilometry) on motor functions that contribute to maintaining an upright body posture in patients with mild gait disturbances. Material and methods. An open descriptive study was conducted including 12 patients (7 men, 5 women), aged 40 to 62 years, with upright posture maintaining disorders, which correspond to the functional diagnosis encoded by the ICF «Gait Stereotype Functions» B770.1 – mild violations (5–24%). A group of subjects (n = 12), in addition to basic therapy and training with an exercise therapy instructor, underwent aquatic training in fresh water for two weeks (30 minutes, 6 days a week). Assessment methods: the research was carried out using the Habilect gait video analysis system before and after the rehabilitation course. The χ2 test was used to assess the significance of differences between groups of qualitative variables. When analyzing quantitative variables, the Shapiro-Wilk’s (W) test was performed. For abnormal distribution, the data is in Me format [Q25-Q75]. The Wilcoxon T-test was used to assess the significance of differences in quantitative variables of the two studied groups. The processing of the obtained research results was carried out using the Statistica for Windows, v. 8.0 (StatSoft Inc., USA) and Microsoft Excel (Microsoft, USA). The significance of the differences was considered established at p <0.05. Result and discussion. When examining the amplitude of body deflection along the X-axis before training, they were 3.25 cm [-98 cm; 93.9 cm], after – -9.96 cm [-100.92 cm; -81.96 cm], on the Y-axis before training – -29.01 cm [-29.01 cm; 13.76 cm], after –-30.59 cm [-30.59 cm; 31.09 cm], on the Z-axis before training – 388.1 cm [369.22 cm; 393.39 cm], after training – 380.96 cm [377.98cm, 400.05 cm], deviation of the body movement vector before training 16.45 cm [7.46 cm; 338.67 cm], after training – 324.7 cm [324.7 cm; 342.56 cm]. When examining the amplitude of head deflection along the X-axis before training, they were -0.92 cm [-1.24 cm; -0.92 cm], after – 1.5 cm [-10.19 cm; 2.38 cm], Y-axis before training – 125.33 cm [61.13 cm; 128.94 cm], after – 107.42 cm [52.49 cm; 107.42 cm], along the Z-axis before training – -8.59 cm [-8.97 cm; -5.33 cm], after training – -14.89 cm [-14.89 cm, -3.45cm]. When calculating the increase in deviation (deviations of the main body axes from the initial value) using the Wilcoxon T-test revealed statistically significant deviations in the X-axis (an increase of 306.5%, p = 0.0504), the Z-axis (an increase of 112.68%, p =0.0225) and the Body Angle parameter (an increase of 1973.86% p = 0.0323). When calculating the increase in the deviation of the head axes from the initial value using the Wilcoxon T-test, statistically significant deviations were revealed along the X axis (increase of 163.04%, p = 0.0280), the Y axis (increase of 85.71%, p = 0.0199) and the parameter Z (an increase of 173.34% p = 0.0292). The study revealed a decrease in the body axes deviations amplitude in all 3 planes, which indicates an improvement in the work of all brain parts that are responsible for the coordination of motor functions and their vegetative support, an improvement in functional interaction within individual muscle chains. The reduction in the head and neck muscles in compensatory balancing participation during walking and maintaining a vertical body posture mainly due to the muscles of the lower extremities and pelvis contributes to the prevention of arterial and venous circulation disorders in the head and neck and makes training not only more effective, but also safer. Conclusion. Due to the decrease in the amplitude of deviations along all three axes (Z, Y, X), the course of aquatic training contributes to the correction of upright posture maintaining disorders, a statistically significant decrease in the amplitude of head and neck movements.

Modified couple stress-based nonlinear static bending and transient responses of size-dependent sandwich microplates with graphene nanocomposite and porous layers

This paper investigates the nonlinear static bending and dynamic transient responses of the rectangular and circular sandwich microplates composed of functionally graded graphene nanocomposite (GNC) face sheets and a porous polymeric core layer based on the modified couple stress theory (MCST) within the isogeometric analysis (IGA) framework. The four-variable higher-order shear deformation refined plate theory (RPT) and the von Kármán large deflection assumption are synthetically employed to describe the kinematics of the microplate. The nonlinear governing equations of motion are derived from the Hamilton’s principle. The nonlinear bending problem is solved by the Newton–Raphson technique under a displacement criterion strategy, while the dynamic responses under transient loads are obtained by the Newmark integration scheme in conjunction with Newton–Raphson iterative procedure. Comparisons are carried out to test the accuracy of iteration procedure in present formulation and the reliability in capturing small scale effect of present model. Obtained outcomes reveal that raising the material length scale (MLS) parameter and volume fraction index of graphene nanofillers both leads to reductions in nonlinear static deflections, dynamic amplitudes of deflection and periods of motion. The examples for porosity coefficient show that embedding pores in core layer leads to slight changes in terms of static and dynamic responses and an improvement in weight reduction of the sandwich microplate.

Impact action of a projectiles on special protective structures and ways to increase their protective capacity

A method for studying the reaction of elastic elements of protective structures to a series of impact actions of shells has been developed. In the work, the elastic elements of the protective structure are modeled by homogeneous beams, and the dynamic action of the shells is simulated by instantaneous point-applied forces. A mathematical model of this dynamic process is constructed, which is a boundary value problem for a hyperbolic equation with an irregular right-hand side. The latter is described using Dirac delta functions. Cases of both fixed and free ends of protective elements are considered. The main ideas of perturbation methods are used for the researches carried out in the work. Analytical dependences for the description of elastic deformations of a protective element which are basic for definition of its strength characteristics are received. They and the graphical dependences built on their basis for specific cases show that the dynamic deformations of the protective element for the fixed ends are greater in the case of the projectile closer to its middle, at the same time for the free ends – closer to the end. With regard to the modernization of protective structures, the dynamic effect on their elements can be reduced by using elastic reinforcement or changing the method of fixing the ends of the protective element: elastic or with a certain angle of inclination of the bearing surfaces. It is proposed to use special plastics, soil layer, flexible wood flooring, etc. as elastic reinforcement. The technique used in the work is the basis for determining the strength characteristics of protective elements, and from so – to check the reliability of the protective structure; study of the dynamics of protective and similar types of structures, taking into account the nonlinear characteristics of the elastic elements of protective structures; study of more complex oscillations of elements of protective structures. In the case of a series of impacts, it is obvious that the amplitude of deflection of the protective element after each impact will increase over time, because the model does not take into account the force of viscoelastic friction. These tasks will be the subject of further research.

Rivulet deflection in the heated liquid film with different initial characteristics

Analysis of rivulet movement across flow direction in vertical flowing heated liquid film at different Reynolds numbers and initial temperatures was carried out. It is shown, that amplitude of deflection increases substantially at heat fluxes corresponding to the appearance of thermocapillary structures of type A.

Association between Iris Biological Features and Corneal Biomechanics in Myopic Eyes.

Purpose Iris biological features such as surface features and profile characteristics reflected the development of iris stroma and microvessels. Iris vessels and microcirculation are still lack of effective detection methods, and we can directly observe only the iris surface biological characteristics. This cross-sectional study evaluated the association between iris surface biological features and corneal biomechanics in young adults with myopia. Methods We recruited 152 patients with myopia aged ≥18 years, from the Eye Hospital of Wenzhou Medical University, who had complete Corneal Visualization Scheimpflug Technology (Corvis ST) data and graded iris surface features. Iris surface features included crypts, furrows, and color measured from digital slit lamp images. The biomechanical properties of the cornea were assessed using Corvis ST. Only 1 eye of each participant was randomly selected for analysis. Associations between the iris surface features and corneal biomechanics were analyzed using linear regression models. The grade of iris crypts, furrows, and color and corneal biomechanical parameters measured with Corvis ST was the main outcome measures. Results The iris crypts were significantly associated with deflection amplitude at the first applanation (A1 DLA, β = 0.001, P = 0.013), A1 delta arc length (A1 dArcL) (β = −0.001, P = 0.01), maximum delta arc length (dArcLM) (β = −0.004, P = 0.03), and stiffness at the first applanation (SP-A1) (β = −2.092, P = 0.016). The iris furrows were only associated with integrated radius (β = −0.212, P = 0.025). Iris color was found not related with corneal biomechanical parameters measured via Corvis ST. Conclusions Iris surface features were associated with corneal biomechanical properties in myopic eyes; more iris crypts were associated with lower corneal stiffness while more extensive furrows were related with higher corneal stiffness. Iris crypts and furrows may provide useful information on corneal biomechanical properties in myopic eyes.

Corneal ectasia in mothers of Down syndrome children

In this study, corneal findings regarding keratoconus (KC) and early KC among mothers with Down syndrome children (MDS) and a group of age-at-delivery-matched mothers with normal children (MNC) were compared. KC was diagnosed based on the presence of a clinical sign and at least one abnormal tomographic or biomechanical criterion. Early KC was defined as having no clinical sign in the presence of at least one abnormal tomographic or biomechanical criterion. The normal subgroups in each group were compared in terms tomographic and biomechanical parameters. In MDS and MNC, the prevalence rates were 6.5% and 1.6% for KC (P = 0.047), and 30.9% and 14.3% for early KC (P = 0.014), respectively. Comparison between the two normal subgroups showed significant differences in mean index of height asymmetry, irregularity index, anterior asphericity, pentacam random forest index, corneal stiffness parameters at first applanation, deformation amplitude ratios, integrated radius-1 mm, highest concavity deflection amplitude, biomechanical corrected IOP, peak distance, and radius (all P < 0.05). This study showed that MDS are more likely to have KC and also to have thinner, steeper and softer corneas compared to MNC. This results support the need for further work for determining the risk of delivering a child with DS.

Comparisons of corneal biomechanical and tomographic parameters among thin normal cornea, forme\xa0fruste keratoconus, and mild keratoconus

BackgroundTo compare the dynamic corneal response (DCR) and tomographic parameters of thin normal cornea (TNC) with thinnest corneal thickness (TCT) (≤ 500 µm), forme fruste keratoconus (FFKC) and mild keratoconus (MKC) had their central corneal thickness (CCT) matched by Scheimpflug imaging (Pentacam) and corneal visualization Scheimpflug technology (Corvis ST).MethodsCCT were matched in 50 eyes with FFKC, 50 eyes with MKC, and 53 TNC eyes with TCT ≤ 500 µm. The differences in DCR and tomographic parameters among the three groups were compared. The receiver operating characteristic (ROC) curve was used to analyze the diagnostic significance of these parameters. Back propagation (BP) neural network was used to establish the keratoconus diagnosis model.ResultsFifty CCT-matched FFKC eyes, 50 MKC eyes and 50 TNC eyes were included. The age and biomechanically corrected intraocular pressure (bIOP) did not differ significantly among the three groups (all P > 0.05). The index of height asymmetry (IHA) and height decentration (IHD) differed significantly among the three groups (all P < 0.05). IHD also had sufficient strength (area under the ROC curves (AUC) > 0.80) to differentiate FFKC and MKC from TNC eyes. Partial DCR parameters showed significant differences between the MKC and TNC groups, and the deflection amplitude of the first applanation (A1DA) showed a good potential to differentiate (AUC > 0.70) FFKC and MKC from TNC eyes. Diagnosis model by BP neural network showed an accurate diagnostic efficiency of about 91%.ConclusionsThe majority of the tomographic and DCR parameters differed among the three groups. The IHD and partial DCR parameters assessed by Corvis ST distinguished FFKC and MKC from TNC when controlled for CCT.

Generation of buckling and wrinkling in elastic films: The effect of initial imperfection.

The symmetry breaking that is induced by initial imperfection (e.g., geometry or material inhomogeneity and out-of-plane disturbance) is a necessary condition for film buckling. However, the effect of initial imperfection on the buckling behavior is still not clear cut. Herein, given an elastic substrate-free circular film subjected to in-plane compressive stress and arbitrary initial imperfection, evolution of the deflection morphology is numerically studied and theoretically analyzed. Specifically, a two-dimensional spatial spectrum analysis is adopted to acquire the deflection morphology's dominant wavelength, which is combined with the maximum absolute deflection to characterize the deflection patterns. Before the so-called critical instability, the film under compression is found to go through a transition stage. Overall, the deflection increment in this stage is negligible except approaching the critical state. However, the dominant wavelength is found to be continuously growing (or decreasing) rather than suddenly appears upon reaching the so-called critical state, and, interestingly, such growth is found to be independent of the intensity and pattern of the initial imperfection if the same initial dominant wavelength is guaranteed. In the discussion, for both the transition and buckling stages, evolution laws of the deflection amplitude and wavelength are established analytically and found to agree well with the numerical results. This research clearly presents the actual evolution process of wrinkling morphology from linear in-plane deformation with small stable deflection to out-of-plane instability with large deflection, which deepens the cognition of instability behavior of films and provides a basis for related applications such as high-precision mechanical characterization.

Mapping Relation between Rail and Bridge Deformation Considering Nonlinear Contact of Interlayer.

This paper examines the effect of structural deformation on the unit slab-type ballastless track structure of high-speed railway. The principle of stationary potential energy was used to map the relation between girder vertical deformation and rail deformation considering the effect of subgrade boundary conditions and the nonlinear contact of interlayer. The theoretical model was verified by comparing with the finite element analysis and experimental results. The theoretical model was used to analyze the effects of several key parameters on the rail deformation, such as vertical deformation amplitude, elastic modulus of the mortar layer, and vertical stiffness of the fasteners. The results show that the track slabs suffered significant disengagement, which makes the deformation of the track structure at the position of the beam joint tend to be gentle when nonlinear contact between the mortar layer and the track slabs was considered. The track slabs disengagement mainly occurs near the beam joints (the side of the deformed beam). As the deflection amplitude of the girder increases, the track deformation, the fastener forces and the disengagement length of the track slabs are obviously nonlinear. When the vertical stiffness of the fastener and/or the elastic modulus of the mortar layer increase, the fastener force and the track plate disengagement length increase monotonically and nonlinearly, which will adversely affect the life and safety of the track structure.

On the subject of analyzing the post-buckling behavior of composite sandwich panels with thin skins of variable stiffness under longitudinal compression

The use of variable stiffness panels can be considered as one of the measures to improve the weight efficiency of aircraft structures. The object of research in this work is three-layer panels of variable stiffness loaded with longitudinal compressive forces. The purpose of the work is to evaluate the overcritical behavior of the specified panels when geometrically nonlinear relations are used. The variable parameter of three-layered panels in the case under consideration is the height of the rigid filler, which varies linearly. An analytical solution of the problem of determining the stress-strain state by the Bubnov-Galerkin method is given. The deflection of a panel is represented by two terms, and the problem is reduced to the solution of a nonlinear system of two unknown equations with respect to the values of the deflection amplitudes. Analytical expressions for calculating membrane stresses are given. The practical significance of the work lies in the possibility of estimating the overcritical behavior of a three-layer panel of variable stiffness under compression and the possibility of constructing an algorithm for the optimal design of the panels.

Dynamics of tethered membranes in inviscid flow

We investigate the dynamics of membranes that are held by freely-rotating rigid tethers in fluid flows. The tethered boundary condition allows periodic and chaotic oscillatory motions for certain parameter values. We characterize the oscillations in terms of deflection amplitudes, dominant periods, and numbers of local extrema of deflection along the membranes across the parameter space of membrane mass density, stretching modulus, pretension, and tether length. We determine the region of instability and the small-amplitude behavior by solving a nonlinear eigenvalue problem. We also consider an infinite periodic membrane model, which yields a regular eigenvalue problem, analytical results, and asymptotic scaling laws. We find qualitative similarities among all three models in terms of the oscillation frequencies and membrane shapes at small and large values of membrane mass, pretension, and tether length/stiffness.

3D numerical simulation of ribbon electron beam bending by relativistic proton bunch

Nowadays experiments in the field of high-energy physics require increasing the intensity and brightness of charged particle beams and developing new methods for their diagnosis. One of the noninvasive methods for diagnosing the parameters of an intense bunch of charged particles is based on the use of a low-energy ribbon electron beam. This paper presents a numerical model of the interaction process of the testing electron beam and the proton bunch under study. The model used to solve the problem consists of the equations of motion of the electron beam under the action of an electromagnetic field created by the relativistic proton bunch. The beam is modeled by calculating of electron trajectories passing through the 3D computational domain. The dependence of the electron beam deflection on its energy, the angle of inclination to the direction of the proton bunch, the magnitude of the space charge and the velocity of the proton bunch is investigated. It is shown that the amplitude of the electron beam deflection is proportional to the charge and gamma factor of the proton bunch and inversely proportional to the energy of the electron beam.

Detection of postlaser vision correction ectasia with a new combined biomechanical index.

To validate and evaluate the use of a new biomechanical index known as the Corvis biomechanical index-laser vision correction (CBI-LVC) as a method for separating stable post-LVC eyes from post-LVC eyes with ectasia. 10 clinics from 9 countries. Retrospective, multicenter, clinical study. The study was designed with 2 purposes: to develop the CBI-LVC, which combines dynamic corneal response (DCR) parameters provided by a high-speed dynamic Scheimpflug camera (CorVis ST; OCULUS Optikgeräte GmbH) and then to evaluate its ability to detect post-LVC ectasia. The CBI-LVC includes integrated inverse radius, applanation 1 (A1) velocity, A1 deflection amplitude, highest concavity and arclength, deformation amplitude ratio of 2 mm, and A1 arclength in millimeters. Logistic regression with Wald forward stepwise approach was used to identify the optimal combination of DCRs to create the CBI-LVC and then separate stable from LVC-induced ectasia. Eighty percentage of the database was used for training the software and 20% for validation. 736 eyes of 736 patients were included (685 stable LVC and 51 post-LVC ectasia). The receiver operating characteristic curve analysis showed an area under the curve of 0.991 when applying CBI-LVC in the validation dataset and 0.998 in the training dataset. A cutoff of 0.2 was able to separate stable LVC from ectasia with a sensitivity of 93.3% and a specificity of 97.8%. The CBI-LVC was highly sensitive and specific in distinguishing stable from ectatic post-LVC eyes. Using CBI-LVC in routine practice, along with topography and tomography, can aid the early diagnosis of post-LVC ectasia and allow intervention prior to visually compromising progression.