Efficacy of scleral buckling for the treatment of rhegmatogenous retinal detachment using a novel foldable capsular buckle

●AIM:To evaluate the effectiveness and safety of scleral buckling for the treatment of rhegmatogenous retinal detachment(RRD)using a novel foldable capsular buckle(FCB).●METHODS:This was a series of case observation studies.Eighteen patients(18 eyes)who visited our ophthalmology department between August 2020 and August 2022 and were treated for RRD with scleral buckling using FCB were included.The procedure was similar to conventional scleral buckling,while a balloon-like FCB was placed onto the retinal break with balanced salt solution filling for a broad,external indentation instead of the silicone buckle.The retinal reattachment rate,best corrected visual acuity(BCVA),intraocular pressure(IOP),refractive dioptre and astigmatism degree,and complications were evaluated and recorded.●RESULTS:There were 7 males and 11 females aged 19-58y.The average time course of RRD was 12d,ranging from 7-20d.The retinal break was located in the superior quadrants in 8 eyes and in the inferior quadrants in 10 eyes,with macula-off detachments in 12 eyes.The patients were followed-up for at least 6mo.The final retinal reattachment rate was 100%.The BCVA was significantly improved compared with the baseline(P<0.05).There was no significant change in refractive dioptre or astigmatism degree at each follow-up(all P>0.05).Three patients had transiently high IOPs within one week after surgery.Mild diplopia occurred in 5 patients after surgery and then disappeared after the balloon fluid was removed.●CONCLUSION:The success rate of FCB scleral buckling for RRD is satisfactory.This procedure can be expected to be applied in new,uncomplicated cases of RRD.

Buckling Properties of Water-Drop-Shaped Pressure Hulls with Various Shape Indices Under Hydrostatic External Pressure

The water-drop-shaped pressure hull has a good streamline,which has good application prospect in the underwater observatory.Therefore,this study conducted analytical,experimental and numerical investigation of the buckling properties of water-drop-shaped pressure hulls under hydrostatic pressure.A water-drop experiment was conducted to design water-drop-shaped pressure hulls with various shape indices.The critical loads for the water-drop-shaped pressure hulls were resolved by using Mushtari’s formula.Several numerical simulations including linear buckling analysis and nonlinear buckling analysis including eigenmode imperfections were performed.The results indicated that the critical loads resolved by Mushtari's formula were in good agreement with the linear buckling loads from the numerical simulations.This formula can be extended to estimate the buckling capacity of water-drop-shaped pressure hulls.In addition,three groups of pressure hulls were fabricated by using stereolithography,a rapid prototyping technique.Subsequently,three groups of the pressure hulls were subjected to ultrasonic measurements,optical scanning,hydrostatic testing and numerical analysis.The experimental results were consistent with the numerical results.The results indicate that the sharp end of the water-drop-shaped pressure hulls exhibited instability compared with the blunt end.This paper provides a new solution to the limitations of experimental studies on the water-drop-shaped pressure hulls as well as a new configuration and evaluation method for underwater observatories.

A non-probabilistic reliability topology optimization method based on aggregation function and matrix multiplication considering buckling response constraints

A non-probabilistic reliability topology optimization method is proposed based on the aggregation function and matrix multiplication.The expression of the geometric stiffness matrix is derived,the finite element linear buckling analysis is conducted,and the sensitivity solution of the linear buckling factor is achieved.For a specific problem in linear buckling topology optimization,a Heaviside projection function based on the exponential smooth growth is developed to eliminate the gray cells.The aggregation function method is used to consider the high-order eigenvalues,so as to obtain continuous sensitivity information and refined structural design.With cyclic matrix programming,a fast topology optimization method that can be used to efficiently obtain the unit assembly and sensitivity solution is conducted.To maximize the buckling load,under the constraint of the given buckling load,two types of topological optimization columns are constructed.The variable density method is used to achieve the topology optimization solution along with the moving asymptote optimization algorithm.The vertex method and the matching point method are used to carry out an uncertainty propagation analysis,and the non-probability reliability topology optimization method considering buckling responses is developed based on the transformation of non-probability reliability indices based on the characteristic distance.Finally,the differences in the structural topology optimization under different reliability degrees are illustrated by examples.

Fault Diagnosis for Buckling Friction Components in Wet Multi-Disc Clutches Using IHHT

The wet multi-disc clutches are extensively used in various transmission systems,withone of the most prevalent failure modes being the buckling deformation of friction components.Animproved Hilbert-Huang transform method(IHHT)is proposed to address the limitations of tradi-tional time-domain vibration analyses,such as low accuracy and mode mixing.This paper first clas-sifies the buckling degree of the friction components.Next,wavelet packet transform(WPT)isapplied to the vibration signals of different buckling plates to partition them into distinct fre-quency bands.Then,the instantaneous features are extracted by empirical mode decomposition(EMD)and Hilbert transform(HT)to discarding extraneous intrinsic mode function(IMF)com-ponents.Comparative analyses of Hilbert spectral entropy and time-domain features confirm theenhanced precision of IHHT under specific classifiers,which is better than traditional methods.

Non-contact wide-field viewing system-assisted scleral buckling surgery for retinal detachment in silicone oilfilled eyes

AIM:To evaluate scleral buckling(SB)surgery using a noncontact wide-field viewing system and 23-gauge intraocular illumination for the treatment of rhegmatogenous retinal detachment in silicone oil(SO)-filled eyes.METHODS:Totally 9 patients(9 eyes)with retinal detachment in SO-filled eyes were retrospectively analyzed.All patients underwent non-contact wide-field viewing system-assisted buckling surgery with 23-gauge intraocular illumination.SO was removed at an appropriate time based on recovery.The patients were followed up for at least 3mo after SO removal.Retinal reattachment,complications,visual acuity and intraocular pressure(IOP)before and after surgery were observed.RESULTS:Patients were followed up for a mean of 8.22mo(3-22mo)after SO removal.All patients had retinal reattachment.At the final follow-up,visual acuity showed improvement for 8 patients,and no change for 1 patient.The IOP was high in 3 patients before surgery,but it stabilized after treatment;it was not affected in the other patients.None of the patients had infections,hemorrhage,anterior ischemia,or any other complication.CONCLUSION:This new non-contact wide-field viewing system-assisted SB surgery with 23-gauge intraocular illumination is effective and safe for retinal detachment in SO-filled eyes.

Buckling Optimization of Curved Grid Stiffeners through the Level Set Based Density Method

Stiffened structures have great potential for improvingmechanical performance,and the study of their stability is of great interest.In this paper,the optimization of the critical buckling load factor for curved grid stiffeners is solved by using the level set based density method,where the shape and cross section(including thickness and width)of the stiffeners can be optimized simultaneously.The grid stiffeners are a combination ofmany single stiffenerswhich are projected by the corresponding level set functions.The thickness and width of each stiffener are designed to be independent variables in the projection applied to each level set function.Besides,the path of each single stiffener is described by the zero iso-contour of the level set function.All the single stiffeners are combined together by using the p-norm method to obtain the stiffener grid.The proposed method is validated by several numerical examples to optimize the critical buckling load factor.

Chebyshev polynomial-based Ritz method for thermal buckling and free vibration behaviors of metal foam beams

This study presents the Chebyshev polynomials-based Ritz method to examine the thermal buckling and free vibration characteristics of metal foam beams.The analyses include three models for porosity distribution and two scenarios for thermal distribution.The material properties are assessed under two conditions,i.e.,temperature dependence and temperature independence.The theoretical framework for the beams is based on the higher-order shear deformation theory,which incorporates shear deformations with higher-order polynomials.The governing equations are established from the Lagrange equations,and the beam displacement fields are approximated by the Chebyshev polynomials.Numerical simulations are performed to evaluate the effects of thermal load,slenderness,boundary condition(BC),and porosity distribution on the buckling and vibration behaviors of metal foam beams.The findings highlight the significant influence of temperature-dependent(TD)material properties on metal foam beams'buckling and vibration responses.

Free vibration and buckling analysis of polymeric composite beams reinforced by functionally graded bamboo fbers

Natural fibers have been extensively researched as reinforcement materials in polymers on account of their environmental and economic advantages in comparison with synthetic fibers in the recent years.Bamboo fibers are renowned for their good mechanical properties,abundance,and short cycle growth.As beams are one of the fundamental structural components and are susceptible to mechanical loads in engineering applications,this paper performs a study on the free vibration and buckling responses of bamboo fiber reinforced composite(BFRC)beams on the elastic foundation.Three different functionally graded(FG)layouts and a uniform one are the considered distributions for unidirectional long bamboo fibers across the thickness.The elastic properties of the composite are determined with the law of mixture.Employing Hamilton’s principle,the governing equations of motion are obtained.The generalized differential quadrature method(GDQM)is then applied to the equations to obtain the results.The achieved outcomes exhibit that the natural frequency and buckling load values vary as the fiber volume fractions and distributions,elastic foundation stiffness values,and boundary conditions(BCs)and slenderness ratio of the beam change.Furthermore,a comparative study is conducted between the derived analysis outcomes for BFRC and homogenous polymer beams to examine the effectiveness of bamboo fibers as reinforcement materials,demonstrating the significant enhancements in both vibration and buckling responses,with the exception of natural frequencies for cantilever beams on the Pasternak foundation with the FG-◇fiber distribution.Eventually,the obtained analysis results of BFRC beams are also compared with those for carbon nanotube reinforced composite(CNTRC)beams found in the literature,indicating that the buckling loads and natural frequencies of BFRC beams are lower than those of CNTRC beams.

Non-linear buffeting response analysis of long-span suspension bridges with central buckle

The rigid central buckle employed in the Runyang Suspension Bridge (RSB) was the first time it was used in a suspension bridge in China. By using a spectral representation method and FFT technique combined with measured data,a 3D fluctuating wind field considering the tower wind effect is simulated. A novel FE model for buffeting analysis is then presented,in which a specific user-defined Matrix27 element in ANSYS is employed to simulate the aeroelastic forces and its stiffness or damping matrices are parameterized by wind velocity and vibration frequency. A nonlinear time history analysis is carried out to study the influence of the rigid central buckle on the wind-induced buffeting response of a long-span suspension bridge. The results can be used as a reference for wind resistance design of long-span suspension bridges with a rigid central buckle in the future.

Analytical modeling for rapid design of bistable buckled beams

Double-clamped bistable buckled beams demonstrate great versatility in various fields such as robotics,energy harvesting,and microelectromechanical system(MEMS).However,their design often requires time-consuming and expensive computations.In this work,we present a method to easily and rapidly design bistable buckled beams subjected to a transverse point force.Based on the Euler–Bernoulli beam theory,we establish a theoretical model of bistable buckled beams to characterize their snapthrough properties.This model is verified against the results from a finite element analysis(FEA)model,with maximum discrepancy less than 7%.By analyzing and simplifying our theoretical model,we derive explicit analytical expressions for critical behavioral values on the force-displacement curve of the beam.These behavioral values include critical force,critical displacement,and travel,which are generally sufficient for characterizing the snapthrough properties of a bistable buckled beam.Based on these analytical formulas,we investigate the influence of a bistable buckled beam's key design parameters,including its actuation position and precompression,on its critical behavioral values,with our results validated by FEA simulations.Our analytical method enables fast and computationally inexpensive design of bistable buckled beams and can guide the design of complicated systems that incorporate bistable mechanisms.

Influence of central buckle on suspension bridge dynamic characteristics and driving comfort

The central buckle, which is often used in a suspension bridge, can improve bridges' performance in the actual operation condition. The influence of the central buckle on natural vibration characteristics and bridge-deck driving comfort of a long-span suspension bridge is studied by using a case study of Siduhe Suspension Bridge in China. Based on the finite element software ANSYS and independently complied program, the influence of the central buckle on the structure force-applied characteristics of a long-span suspension bridge has been explored. The results show that the huge increases of natural frequencies can result in the presence of central buckles because of the increases of bending and torsional rigidities. The central buckle basically makes the stiffening girders and cables within the triangular area covered as a relatively approximate rigid area. Hence, the central buckle can reduce the torsional displacement of the main girder. However, the increases of bending and torsional rigidities have little influence on the impact factor, which is obtained by using vehicle-bridge coupled vibration analysis. This means that the central buckle has little effect on the comfort indices. In addition, it is found that the central buckle can enhance the bridge deck's driving stability due to the decrease of the torsional displacements of the main girder.

Influence of rigid central buckle on seismic response of long-span suspension bridges

A rigid central buckle is employed in Runyang Suspension Bridge （RSB） to replace commonly used short suspenders in the main span. Based on the seismic waves with 2% probabilities of exceedance, the nonlinear seismic response time-domain analysis are then conducted and influence of central buckles on seismic response of long-span suspension bridge is specially studied. Analysis resuits show that the central buckle can effectively control the longitudinal floating vibration mode of the deck, and therefore reduce earthquake-excited longitudinal displacement at the end of the deck. However, the central buckle may cause increment of longitudinal displacement at the top of main tower and bending moment at the bottom of the main tower, which should be paid special attention to. Results provide references for anti-earthquake analysis and design of long-span suspension bridges using rigid central buckles.

Electronic,Elastic and Piezoelectric Properties of Two-Dimensional Group-Ⅳ Buckled Monolayers

Electronic, elastic and piezoelectric properties of two-dimensional （2D） group-IV buckled monolayers （GeSi, SnSi and SnGe） are studied by first principle calculations. According to our calculations, SnSi and SnGe are good 2D piezoelectric materials with large piezoelectric coefficients. The values of d11d11 of SnSi and SnGe are 5.04pm/V and 5.42pm/V, respectively, which are much larger than 2D MoS2 （3.6pm/V） and are comparable with some frequently used bulk materials （e.g., wurtzite AlN 5.1pm/V）. Charge transfer is calculated by the L wdin analysis and we find that the piezoelectric coefficients （d11d11 and d31） are highly dependent on the polarizabilities of the anions and cations in group-IV monolayers.

Nonlinear Contact Between Pipeline's Outer Wall and Slip-on Buckle Arrestor's Inner Wall During Buckling Process

In order to theoretically study the buckle propagation of subsea pipelines with slip-on buckle arrestors, a two-dimensional ring model was set up to represent the pipeline and a nonlinear spring model was adopted to simulate the contact between pipeline's inner walls and between pipeline's outer wall and slip-on buckle arrestor's inner wall during buckle propagation. In addition, some reverse springs are added to prevent the wall of left and right sides separating from the inner wall of slip-on buckle arrestors. Considering large deformation kinematics relations and the elastic-plastic constitutive relation of material, balance equations were established with the principle of virtual work. The variation of external pressure with respect to the cross-sectional area of pipelines was analyzed, and the lower bound of the crossover pressure of slip-on buckle arrestors was calculated based on Maxwell's energy balance method. By comparing the theoretical results with experiment and finite element numerical simulation, the theoretical method is proved to be correct and reliable.

Analysis of Stability and Large Deflection Buckle of Rolled Strip by Third Power B-Spline Function Method

A new method——the third power B-spline function method is developed to analyse the stability and the buckle of rolled strip under residual stress.The large deflection theory of thin plate is used to calculate the buckle of rolled strip and criterion of critical buckle is given.The computed results tally with those of experiment well,which provides theoretical basis and method for developing the mathematical model of flatness control.

DYNAMIC ANALYSIS OF ARREST OF BUCKLE PROPAGATION ON A BEAM ON A NONLINEAR ELASTIC FOUNDATION BY FEM

Based on the dynamic governing equation of propagating buckle on a beam on a nonlinear elastic foundation, this paper deals with an important problem of buckle arrest by combining the FEM with a time integration technique. A new conclusion completely different from that by the quasi-static analysis about the buckle arrestor design is drawn. This shows that the inertia of the beam cannot be ignored in the analysis under consideration, especially when the buckle propagation is suddenly stopped by the arrestors.

Dynamic Analysis and Numerical Simulation of a Kind of Arrestor Arresting Buckle Propagation by FEM

For exact estimation of efficiency of a buckle arrestor, it is necessary to take the effect of structural inertia into account in the analysis of buckle propagation on elastic structures after meeting arrestors. Under this consideration, this paper deals with the dynamics of buckle arrest and its numerical simulation on the basis of the beam system model used by Chater and Hutchinson (1983). The FEM combined with an improving are-length control method is adopted to solve the dynamic equations describing the arresting of buckle propagation. A new group of parameters for arrestor design which differs greatly from that by the quasi-static analysis is obtained. The present results support the conclusion that the inertia of the beam cannot be neglected in such analysis.

THE BUCKLED STATES OF ANNULAR SANDWICH PLATES

In this paper, the axisymmetric buckled states of an annular sandwich plate ( Reissner-type sandwich plate) with the clamped inner edge which is subjected to a uniform radial compressive thrust at the clamped outer edge are studied. Firstly, the basic equation of the buckled problem is derived. Secondly, the critical loads for some parameters are obtained by using the shooting method. Finally, we discuss the existence of the buckled slates in the vicinity of the critical loads and obtain the asymptotic expansions of the buckled states.

A METHOD OF DETERMINING BUCKLED STATES OF THIN PLATES AT A DOUBLE EIGENVALUE

A method of determining bifurcation directions at a double eigenvalue is presented by combining the finite element method with the perturbation method. By using the present method, the buckled states of rectangular plates at a double eigenvalue are numerically analyzed. The results show that this method is effective.

Dirac states from p_(x,y)orbitals in the buckled honeycomb structures:A tight-binding model and first-principles combined study

Dirac states composed of Px,y orbitals have been reported in many two-dimensional （2D） systems with honeycomb lattices recently. Their potential importance has aroused strong interest in a comprehensive understanding of such states. Here, we construct a four-band tight-binding model for the Px,y-orbital Dirac states considering both the nearest neighbor hopping interactions and the lattice-buckling effect. We find that Px,y-orbital Dirac states are accompanied with two addi- tional narrow bands that are flat in the limit of vanishing n bonding, which is in agreement with previous studies. Most importantly, we analytically obtain the linear dispersion relationship between energy and momentum vector near the Dirac cone. We find that the Fermi velocity is determined not only by the hopping through n bonding but also by the hopping through ~ bonding of Px,y orbitals, which is in contrast to the case of pz-orbital Dirac states. Consequently, Px,y-orbital Dirac states offer more flexible engineering, with the Fermi velocity being more sensitive to the changes of lattice constants and buckling angles, if strain is exerted. We further validate our tight-binding scheme by direct first-principles calcula- tions of model-materials including hydrogenated monolayer Bi and Sb honeycomb lattices. Our work provides a more in-depth understanding of Px,y-orbital Dirac states in honeycomb lattices, which is useful for the applications of this family of materials in nanoelectronics.