Long-term risk prediction after major lower limb amputation: 1-year results of the PERCEIVE study

Background: Decision-making when considering major lower limb amputation is complex and requires individualized outcome estimation. It is unknown how accurate healthcare professionals or relevant outcome prediction tools are at predicting outcomes at 1-year after major lower limb amputation. Methods: An international, multicentre prospective observational study evaluating healthcare professional accuracy in predicting outcomes 1 year after major lower limb amputation and evaluation of relevant outcome prediction tools identified in a systematic search of the literature was undertaken. Observed outcomes at 1 year were compared with: healthcare professionals' preoperative predictions of death (surgeons and anaesthetists), major lower limb amputation revision (surgeons) and ambulation (surgeons, specialist physiotherapists and vascular nurse practitioners); and probabilities calculated from relevant outcome prediction tools. Results: A total of 537 patients and 2244 healthcare professional predictions of outcomes were included. Surgeons and anaesthetists had acceptable discrimination (C-statistic = 0.715), calibration and overall performance (Brier score = 0.200) when predicting 1-year death, but performed worse when predicting major lower limb amputation revision and ambulation (C-statistics = 0.627 and 0.662 respectively). Healthcare professionals overestimated the death and major lower limb amputation revision risks. Consultants outperformed trainees, especially when predicting ambulation. Allied healthcare professionals marginally outperformed surgeons in predicting ambulation. Two outcome prediction tools (C-statistics = 0.755 and 0.717, Brier scores = 0.158 and 0.178) outperformed healthcare professionals' discrimination, calibration and overall performance in predicting death. Two outcome prediction tools for ambulation (C-statistics = 0.688 and 0.667) marginally outperformed healthcare professionals. Conclusion: There is uncertainty in predicting 1-year outcomes following major lower limb amputation. Different professional groups performed comparably in this study. Two outcome prediction tools for death and two for ambulation outperformed healthcare professionals and may support shared decision-making

Assessment of contact-induced damage mechanisms in thick-walled composite cylinders

AbstractIn order to unravel the damage mechanisms occurring in composite-overwrapped pressure vessels (COPVs) subjected to crash conditions, a combined experimental-numerical study has been performed. For the purpose of generality and simplicity, quasi-static contacts on filament-wound cylinders are considered in this paper, as a precursor for geometrically complex impacts on COPVs. Rings with different wall thicknesses are tested to assess how failure mechanisms change when transitioning from thin-wall to thick-wall cylinders. The experimental results are used to identify, which mechanisms occur, and the numerical model is subsequently exploited to analyze the corresponding mechanisms. Based on the understanding of the mechanisms, a method to improve the damage tolerance of thick cylinders is presented. The rings are locally pre-delaminated during manufacturing to promote the growth of these pre-delaminations instead of the initiation of fiber failure

MATLAB scripts of the paper "Homogenized enriched continuum analysis of acoustic metamaterials with negative stiffness and double negative effects"

The associated paper demonstrates, for the first time, the application of a recently developed computational homogenization method towards dynamic analyses of locally resonant acoustic metamaterials (LRAM) exhibiting double negative effects, i.e. simultaneously negative mass and negative stiffness effects within a certain frequency regime. The present method provides an efficient tool for analyses of double negative metamaterials involving non-trivial loading and complex unit cell design. The method above is implemented in MATLAB and the provided MATLAB scripts include:1) Calculation of the frequency-independent dynamic effective material properties for a given LRAM unit cell design. Finite element method is employed.2) Calculation of the dispersion spectra of an infinite LRAM medium, using plane wave transformation. Reference solution by Bloch analysis is given as well.3) Frequency domain analysis of a LRAM prism embedded in a conventional material domain, based on harmonic solution assumption. Individual compressive and shear wave fields are determined as well, using Helmholtz decomposition. Finite element method is employed

MATLAB scripts of the paper "Computational homogenization of locally resonant acoustic metamaterial panels towards enriched continuum beam/shell structures"

The associated paper presents a novel computational homogenization method enabling efficient and accurate modelling of wave propagation phenomena in locally resonant acoustic metamaterial (LRAM) panels, which was not possible for direct numerical simulations as well as available homogenization methods. The proposed method provides a considerable advantage for fast analyses and design of metamaterial panels. The method above is implemented in MATLAB and the provided MATLAB scripts include:1) Calculation of the frequency-independent dynamic effective material properties for a given LRAM unit cell design. Finite element method is employed.2) Dispersion analysis of an infinite LRAM beam, using plane wave transformation.3) Frequency domain analysis of a finite LRAM beam, based on harmonic solution assumption. Isogeometric analysis is employed.4) Transient analysis of a finite LRAM beam. Isogeometric analysis is employed. Time integration is performed using Newmark method. Reference solutions by direct numerical simulations using COMSOL are given as well

MATLAB script and COMSOL models of the article "Transient computational homogenization of heterogeneous poroelastic media with local resonances"

A computational homogenization framework is proposed for solving transient wave propagation in the linear regime in heterogeneous poroelastic media that may exhibit local resonances due to microstructural heterogeneities. The microscale fluid-structure interaction problem and the macroscale are coupled through an extended version of the Hill-Mandel principle, leading to a variationally consistent averaging scheme of the microscale fields. The effective macroscopic constitutive relations are obtained by expressing the microscale problem with a reduced-order model that contains the longwave basis and the so-called local resonance basis, yielding the closed-form expressions for the homogenized material properties. The resulting macroscopic model is an enriched porous continuum with internal variables that represent the microscale dynamics at the macroscale, whereby the Biot model is recovered as a special case. Numerical examples demonstrate the framework’s validity in modeling wave transmission through a porous layer. This software publication provides the MATLAB script and COMSOL models supporting the article

MATLAB scripts of the paper "Efficient and accurate analysis of locally resonant acoustic metamaterial plates using computational homogenization"

The associated paper presents a 3D extension of the recently developed computational homogenization method for locally resonant acoustic metamaterial (LRAM) panels. The developed homogenization method provides a powerful computational tool for efficient and accurate analysis of LRAM panels of finite sizes and arbitrary shape under non-trivial excitations. The method above is implemented in MATLAB and the provided MATLAB scripts include:1) Calculation of the frequency-independent dynamic effective material properties for a given 3D LRAM unit cell design. Finite element method is employed.2) Dispersion analysis of an infinite LRAM plate, using plane wave transformation.3) Frequency domain analysis of a finite LRAM plate, based on harmonic solution assumption. Isogeometric analysis is employed.4) Transient analysis of a finite LRAM plate. Isogeometric analysis is employed. Time integration is performed using Newmark method. 5) Application for the transient analysis of a large finite LRAM plate with a non-trivial non-harmonic excitation imposed. This analysis would be computationally prohibitive to perform by direct numerical simulation.Reference solutions for 2) by Bloch analysis in MATLAB and 3-4) by direct numerical simulations in COMSOL are given as well

MATLAB script and COMSOL models of the article "An efficient multiscale method for subwavelength transient analysis of acoustic metamaterials"

A reduced-order homogenisation framework is proposed in the article "An efficient multiscale method for subwavelength transient analysis of acoustic metamaterials", providing a macro-scale enriched continuum model for locally resonant acoustic metamaterials operating in the subwavelength regime, for both time and frequency domain analyses. The homogenised continuum has a non-standard constitutive model, capturing a metamaterial behaviour such as negative effective bulk modulus, negative effective density, and Willis coupling. A suitable reduced space is constructed based on the unit cell response in a steady state regime and the local resonance regime. - The effective continuum material properties are computed via the MATLAB script provided here. -A frequency domain numerical example demonstrates the efficiency and suitability of the proposed framework. The macro-scale model is implemented via a COMSOL model provided here. -The direct numerical simulations (COMSOL models) are also provided here

LiMeS-lab: An integrated laboratory for the development of Liquid-Metal Shield technologies for fusion reactors

The liquid metal shield laboratory (LiMeS-Lab) will provide the infrastructure to develop, test, and compare liquid metal divertor designs for future fusion reactors. The main research topics of LiMeS-lab will be liquid metal interactions with the substrate material of the divertor, the continuous circulation and capillary refilling of the liquid metal during intense plasma heat loading and the retention of plasma particles in the liquid metal. To facilitate the research, four new devices are in development at the Dutch Institute for Fundamental Energy Research and the Eindhoven University of Technology: LiMeS-AM: a custom metal 3D printer based on powder bed fusion; LiMeS-Wetting, a plasma device to study the wetting of liquid metals on various substrates with different surface treatments; LiMeS-PSI, a linear plasma generator specifically adapted to operate continuous liquid metal loops. Special diagnostic protection will also be implemented to perform measurements in long duration shots without being affected by the liquid metal vapor; LiMeS-TDS, a thermal desorption spectroscopy system to characterize deuterium retention in a metal vapor environment. Each of these devices has specific challenges due to the presence and deposition of metal vapors that need to be addressed in order to function. In this paper, an overview of LiMeS-Lab will be given and the conceptual designs of the last three devices will be presented