Fatigue increases the risk of injury during sports training and rehabilitation. Early detection of fatigue during exercises would help adapt the training in order to prevent over-training and injury. ...This study lays the foundation for a data-driven model to automatically predict the onset of fatigue and quantify consequent fatigue changes using a force plate (FP) or inertial measurement units (IMUs). The force plate and body-worn IMUs were used to capture movements associated with exercises (squats, high knee jacks, and corkscrew toe-touch) to estimate participant-specific fatigue levels in a continuous fashion using random forest (RF) regression and convolutional neural network (CNN) based regression models. Analysis of unseen data showed high correlation (up to 89%, 93%, and 94% for the squat, jack, and corkscrew exercises, respectively) between the predicted fatigue levels and self-reported fatigue levels. Predictions using force plate data achieved similar performance as those with IMU data; the best results in both cases were achieved with a convolutional neural network. The displacement of the center of pressure (COP) was found to be correlated with fatigue compared to other commonly used features of the force plate. Bland-Altman analysis also confirmed that the predicted fatigue levels were close to the true values. These results contribute to the field of human motion recognition by proposing a deep neural network model that can detect fairly small changes of motion data in a continuous process and quantify the movement. Based on the successful findings with three different exercises, the general nature of the methodology is potentially applicable to a variety of other forms of exercises, thereby contributing to the future adaptation of exercise programs and prevention of over-training and injury as a result of excessive fatigue.
In this paper, a multi-scale model for AA3104-H19 and AA2024-T3 aluminium alloy with strong cold rolled crystallographic texture is proposed. This model consists of two components: (i) a full-field ...crystal plasticity spectral method using fast Fourier transformation (CPFFT) that can be used to predict anisotropic mechanical properties in both the in and out-of-plane uniaxial and multi-axial stress states and (ii) a 3D new phenomenological anisotropic yield function with enough flexibility to describe the in and out-of-plane mechanical anisotropies of strongly textured aluminium alloy sheet. This multi-scale model was implemented into a commercial finite element (FE) software Abaqus via a user-defined material subroutine UMAT to predict the anisotropic plastic deformation in a multi-step forming process (deep drawing). Results showed that this new modelling approach is able to accurately predict earing profiles with multiple ears in deep drawn cups based on the crystallographic texture information data obtained from orientation density functions (ODFs).
The mechanical anisotropy of FCC aluminium alloy is influenced by the polycrystalline orientations transformed by cold rolling. The relationship between mechanical anisotropy and evolution of ...crystallographic textures was established using the crystal plasticity finite element method (CPFEM) based on measured polycrystalline orientation density functions (ODFs) and used to determine the parameters of a phenomenological convex anisotropic yield function which are solved with an implicit finite element (FE) stress integration code. A multi-scale modelling system is generated by combining CPFEM and the phenomenological yield function enabling accurate simulations of forming operations without the need for conventional physical mechanical testing of the material.
•Quantify the evolution of texture induced anisotropy of FCC aluminium alloy sheet during cold rolling process.•A multi-scale modelling system is generated by combining crystal plasticity method and phenomenological approach.•The multi-scale modelling system has been shown to accurately predict the deformation of sheet metal in forming process.
Ride comfort refers to human tolerance to vibration exposure over time. Presently, ISO 2631, EN 12,299 and Sperling's method are the most common evaluation methods for assessing passenger comfort on ...trains. It is difficult to establish a universal set of requirements because passengers' perception of comfort may be affected by various factors such as vibration, noise, track condition, etc. In this paper, existing standards and methods for evaluating ride comfort are assessed. A case study of V/Line passenger train in Australia in which the dynamic response is measured and used to evaluate the Continuous Comfort index, Mean Comfort index, and Sperling index. Based on the previous findings and the experimental results, similarities and benefits between these ride comfort methods are analysed and discussed. A new compound Sperling's index is proposed and the correlations of various ride comfort indices are established.
A new anisotropic yield function which accurately describes the complex anisotropy of aluminium alloy sheet metal is proposed in this paper. A non-linear least square method is used to determine the ...coefficients of this yield function based on the experimental results. By employing the back-Euler stress integration algorithm, this anisotropic constitutive model has been successfully implemented in commercial FEM software ABAQUS via user material subroutine UMAT to predict earing profile of AA3104-H19 deep-drawn and redrawn cups. Good agreement was found in the predicted earing profiles and those obtained in experimental deep-drawn and redrawn cups. The FE model was used in an iteration optimisation process to determine the optimal shape of non-round blanks to obtain the ear-free deep-redrawn cups, and non-round tooling was designed accordingly. Results showed the height of the ears is significantly reduced in the cup formed using this non-round blank compared with that of a conventional round blank which is important for smooth running of high-speed multi-step forming of aluminium can body.
•A non-contact and non-destructive laser speckle imaging sensor (LSIS) for surface strain measurement is developed.•The effects of different support conditions on the performance of concrete sleeper ...are quantified using LSIS and strain gauge techniques.•The proposed LSIS is capable of achieving high-resolution strain sensing with a maximum mean absolute error of 5.14 ± 3.12 μ∊ as the detection threshold of 20 μ∊ is exceeded.•The advantages and technical feasibilities of LSIS for in situ strain sensing are demonstrated.
Prestressed concrete sleepers play a significant role in distributing wheel loads from the rails to the ballast layer. Cyclic wheel loads may cause local deterioration of the ballast layer which would affect the support conditions beneath the sleepers. Therefore, understanding the influence of different support conditions on the deformation of sleepers is necessary for maintaining safe railroad operations. In this study, a non-contact and non-destructive laser speckle imaging sensor (LSIS) was developed and successfully applied to investigate the flexural behaviour of concrete sleepers under various support conditions, including “full support”, “partial support” and “centre binding”. The results show that LSIS was in agreement with foil strain gauges of achieving high-resolution strain measurements with a maximum mean absolute error of 5.41±3.12με (equivalent to a mean absolute error of 7.15%) as the detection threshold (20 με) is exceeded. More than three times change in the negative bending moment was observed at the mid-span of the sleeper as the support condition was changed from “full support” to “centre binding”, which indicates the potential risks of voided ballast support and importance of ballast tamping in railway maintenance.
•Waste glass is used as a partial activator and as a mineral precursor in one-part AAMs.•Waste glass powder serves as an effective silica supplier in the solid activator.•Waste glass as a mineral ...precursor retards the early strength of one-part AAMs.•Waste glass-based one-part AAMs are 23% cheaper and 84% greener than OPC binders.
The feasibility of the extensive recycling of waste glass in alkali-activated materials (AAMs) was evaluated. The waste glass was utilised in AAMs for two purposes: a partial activator and a mineral precursor. The waste glass was blended with commercial sodium hydroxide and then heated to produce the solid activator powder. The technical performance of waste glass-based activator was investigated to replace commercial sodium silicate, a common alkali-activator used in AAMs. The effect of waste glass using only as the activator (WGA) and using as both activator and precursor (WGAP) in fly ash/slag-based one-part AAMs was studied using strength and microstructure characterisations. A mass-cost and emission analysis of waste glass-based AAMs (WGA and WGAP) was conducted, comparing the results with ordinary Portland cement (OPC). Characterisation tests of waste glass-based activator showed the effective formation of sodium silicate minerals with the adequate dissolution of activator in water by releasing reactive alkali and silica. Both WGA and WGAP showed comparable strengths at 56 days with a denser microstructure under ambient curing. According to mass analysis, waste glass could be utilised up to 17% by mass of total binder. Based on the analysis of cost and CO2 emissions, WGA and WGAP are around 23% and 15% cheaper and 84% and 82% greener than OPC. The dual role of waste glass in AAMs as an activator and as a precursor broadens the recycling of glass waste in the cement industry by favouring technical and environmental outcomes.
Abstract
Gastrulation begins when the epiblast forms the primitive streak or becomes definitive ectoderm. During this lineage bifurcation, the DNA dioxygenase TET1 has bipartite functions in ...transcriptional activation and repression, but the mechanisms remain unclear. By converting mouse embryonic stem cells (ESCs) into neuroprogenitors, we defined how Tet1–/– cells switch from neuroectoderm fate to form mesoderm and endoderm. We identified the Wnt repressor Tcf7l1 as a TET1 target that suppresses Wnt/β-catenin and Nodal signalling. ESCs expressing catalytic dead TET1 retain neural potential but activate Nodal and subsequently Wnt/β-catenin pathways to generate also mesoderm and endoderm. At CpG-poor distal enhancers, TET1 maintains accessible chromatin at neuroectodermal loci independently of DNA demethylation. At CpG-rich promoters, DNA demethylation by TET1 affects the expression of bivalent genes. In ESCs, a non-catalytic TET1 cooperation with Polycomb represses primitive streak genes; post-lineage priming, the interaction becomes antagonistic at neuronal genes, when TET1’s catalytic activity is further involved by repressing Wnt signalling. The convergence of repressive DNA and histone methylation does not inhibit neural induction in Tet1-deficient cells, but some DNA hypermethylated loci persist at genes with brain-specific functions. Our results reveal versatile switching of non-catalytic and catalytic TET1 activities based on genomic context, lineage and developmental stage.
Femur diaphysis fractures almost always require surgery to heal. The femur recovery process may take 3–6 months or even longer. The current femur recovery assessment methods are qualitative and ...mainly rely on physicians' clinical experience. A better methodology to quantify the healing status will help the physicians counsel their patients on the appropriate load-bearing activities accordingly. This paper numerically and experimentally demonstrates a femur healing assessment methodology using fibre Bragg grating (FBG) sensors. Finite Element (FE) analysis was conducted to confirm the feasibility of the used epoxies. For the experiments, a fourth-generation composite femur (4GCF) sample fixated with an implant plate was prepared. The sample was instrumented with a total of six FBGs on the proximal and distal posterior, mid-shaft, and implant surfaces. The prepared sample was then subjected to cyclic loading on a hydraulic tensile machine in various situations including (1) intact, (2) fractured (mid-shaft transverse and wedge), and (3) epoxy-healed. Epoxies with different curing times were applied on the fractured femur to mimic bone regeneration stages as they harden. FBGs were used to monitor the alterations in the strain values during the healing stages. The results demonstrated that the strain values measured by FBGs were able to justify the non-union, mal-union, delayed union, and fully union conditions on the femur shaft compared to the intact and fractured conditions. The proposed assessment technique can potentially be used on long bones with various fracture types and for patients of different ages and recovery rates.
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•Fractured femur healing process was quantitatively monitored and assessed.•Epoxies were applied on fractured femur to mimic bone regeneration stages as they cure.•Finite element analysis was used to investigate the utilised epoxies feasibility.•The healing extent of the femur is shown at each stage during the recovery time period.
The mechanical anisotropy of aluminium alloy AA2024-T3 with strong cold-rolled crystallographic texture is investigated in this paper. A non-contact and non-destructive laser speckle imaging sensor ...is developed for surface strain measurement so that extensive mechanical tests can be readily performed without surface preparation on the specimens. Both Hill’s 48 and Yld2004-18p yield functions are accurately calibrated using the experimental results from uniaxial tensile, pure shear and plane-strain tensile tests. The constitutive models based on these yield functions were successfully implemented in a commercial finite element (FE) package Abaqus via user material subroutine UMAT. Simulations of single element tensile tests and pure shear tests were carried out to validate the accuracy of UMAT subroutine. The performance of these constitutive models was further evaluated with deep drawing experiments in which the predicted earing profiles were compared with those obtained from FE simulations. The results showed that the constitutive model based on Yld2004-18p yield function accurate representing the anisotropic behaviour of AA2024-T3. The predicted earing profiles coincide well with experimental measurements.
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