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"DIMENSIONAL ANALYSIS"
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Isosurfaces : geometry, topology, and algorithms
\"Ever since Lorensen and Cline published their paper on the marching cubes algorithm, isosurfaces have been a standard technique for the visualization of 3D volumetric data. Yet there is no book exclusively devoted to isosurfaces. This book presents the basic algorithms for isosurface construction and gives a rigorous mathematical perspective to some of the algorithms and results. It offers a solid introduction to research in this area as well as an organized overview of the various algorithms associated with isosurfaces\"-- Provided by publisher.
Book
Linear stability and spectral modal decomposition of three-dimensional turbulent wake flow of a generic high-speed train
This work investigates the spatio-temporal evolution of coherent structures in the wake of a generic high-speed train, based on a three-dimensional database from large eddy simulation. Spectral proper orthogonal decomposition (SPOD) is used to extract energy spectra and energy ranked empirical modes for both symmetric and antisymmetric components of the fluctuating flow field. The spectrum of the symmetric component shows overall higher energy and more pronounced low-rank behaviour compared with the antisymmetric one. The most dominant symmetric mode features periodic vortex shedding in the near wake, and wave-like structures with constant streamwise wavenumber in the far wake. The mode bispectrum further reveals the dominant role of self-interaction of the symmetric component, leading to first harmonic and subharmonic triads of the fundamental frequency, with remarkable deformation of the mean field. Then, the stability of the three-dimensional wake flow is analysed based on two-dimensional local linear stability analysis combined with a non-parallelism approximation approach. Temporal stability analysis is first performed for both the near-wake and the far-wake regions, showing a more unstable condition in the near-wake region. The absolute frequency of the near-wake eigenmode is determined based on spatio-temporal analysis, then tracked along the streamwise direction to find out the global mode growth rate and frequency, which indicate a marginally stable global mode oscillating at a frequency very close to the most dominant SPOD mode. The global mode wavemaker is then located, and the structural sensitivity is calculated based on the direct and adjoint modes derived from a local spatial analysis, with the maximum value localized within the recirculation region close to the train tail. Finally, the global mode shape is computed by tracking the most spatially unstable eigenmode in the far wake, and the alignment with the SPOD mode is computed as a function of streamwise location. By combining data-driven and theoretical approaches, the mechanisms of coherent structures in complex wake flows are well identified and isolated.
Journal Article
Single-snapshot machine learning for super-resolution of turbulence
Modern machine-learning techniques are generally considered data-hungry. However, this may not be the case for turbulence as each of its snapshots can hold more information than a single data file in general machine-learning settings. This study asks the question of whether nonlinear machine-learning techniques can effectively extract physical insights even from as little as a single snapshot of turbulent flow. As an example, we consider machine-learning-based super-resolution analysis that reconstructs a high-resolution field from low-resolution data for two examples of two-dimensional isotropic turbulence and three-dimensional turbulent channel flow. First, we reveal that a carefully designed machine-learning model trained with flow tiles sampled from only a single snapshot can reconstruct vortical structures across a range of Reynolds numbers for two-dimensional decaying turbulence. Successful flow reconstruction indicates that nonlinear machine-learning techniques can leverage scale-invariance properties to learn turbulent flows. We also show that training data of turbulent flows can be cleverly collected from a single snapshot by considering characteristics of rotation and shear tensors. Second, we perform the single-snapshot super-resolution analysis for turbulent channel flow, showing that it is possible to extract physical insights from a single flow snapshot even with inhomogeneity. The present findings suggest that embedding prior knowledge in designing a model and collecting data is important for a range of data-driven analyses for turbulent flows. More broadly, this work hopes to stop machine-learning practitioners from being wasteful with turbulent flow data.
Journal Article
Three-dimensional stability of natural convection flows in inclined square enclosures
The three-dimensional stability of two-dimensional natural convection flows in a heated, square enclosure inclined to the horizontal is investigated numerically. First, the computational procedure is validated by comparison of base flow solutions to results reported in literature across a range of inclinations. A bi-global linear stability analysis is then conducted to investigate the stability of these two-dimensional base flows to infinitesimal three-dimensional perturbations, and the effect that buoyancy forces (defined by a buoyancy number $R_N$) and enclosure inclination $\\theta$ have on these stability characteristics. The flow is first observed to become three-dimensionally unstable at buoyancy number $R_N = 213.8$ when $\\theta$ is $180^\\circ$; this increases to $R_N = 2.54 \\times 10^4$ at inclination $\\theta =58^\\circ$. It is found that the two-dimensional base flow is more unstable to three-dimensional perturbations with the critical $R_N$ corresponding to three-dimensional instability being significantly lower than its two-dimensional counterpart across all considered inclinations except $83^\\circ \\leq \\theta \\leq 88^\\circ$, where the most unstable mode is a two-dimensional oscillatory mode that develops in the boundary layers along the conducting walls. Eight different leading three-dimensional instability modes are identified, with inclinations $58^\\circ \\leq \\theta < 88^\\circ$ transitioning through an oscillatory mode, and inclinations $88^\\circ \\leq \\theta \\leq 180^\\circ$ transitioning through a stationary mode. The characteristics of the primary instability modes corresponding to inclinations $88^\\circ \\leq \\theta \\leq 179^\\circ$ indicate the presence of a Taylor–Görtler instability.
Journal Article
Two-dimensional motion analysis of dynamic knee valgus identifies female high school athletes at risk of non-contact anterior cruciate ligament injury
Purpose
Female athletes are at greater risk of non-contact ACL injury. Three-dimensional kinematic analyses have shown that at-risk female athletes have a greater knee valgus angle during drop jumping. The purpose of this study was to evaluate the relationship between knee valgus angle and non-contact ACL injury in young female athletes using coronal-plane two-dimensional (2D) kinematic analyses of single-leg landing.
Methods
Two hundred ninety-one female high school athletes newly enrolled in basketball and handball clubs were assessed. Dynamic knee valgus was analysed during single-leg drop jumps using 2D coronal images at hallux–ground contact and at maximal knee valgus. All subjects were followed up for 3 years for ACL injury. Twenty-eight (9.6%) of 291 athletes had ACL rupture, including 27 non-contact ACL injuries. The injured group of 27 knees with non-contact ACL injury was compared with a control group of 27 randomly selected uninjured knees. The relationship between initial 2D movement analysis results and subsequent ACL injury was investigated.
Results
Dynamic knee valgus was significantly greater in the injured group compared to the control group at hallux–ground contact (2.1 ± 2.4 vs. 0.4 ± 2.2 cm,
P
= 0.006) and at maximal knee valgus (8.3 ± 4.3 vs. 5.1 ± 4.1 cm,
P
= 0.007).
Conclusion
The results of this study confirm that dynamic knee valgus is a potential risk factor for non-contact ACL injury in female high school athletes. Fully understanding the risk factors that increase dynamic knee valgus will help in designing more appropriate training and interventional strategies to prevent injuries in at-risk athletes.
Level of evidence
Prognostic studies, Level II.
Journal Article
The social and structural architecture of the yeast protein interactome
Cellular functions are mediated by protein–protein interactions, and mapping the interactome provides fundamental insights into biological systems. Affinity purification coupled to mass spectrometry is an ideal tool for such mapping, but it has been difficult to identify low copy number complexes, membrane complexes and complexes that are disrupted by protein tagging. As a result, our current knowledge of the interactome is far from complete, and assessing the reliability of reported interactions is challenging. Here we develop a sensitive high-throughput method using highly reproducible affinity enrichment coupled to mass spectrometry combined with a quantitative two-dimensional analysis strategy to comprehensively map the interactome of
Saccharomyces cerevisiae
. Thousand-fold reduced volumes in 96-well format enabled replicate analysis of the endogenous GFP-tagged library covering the entire expressed yeast proteome
1
. The 4,159 pull-downs generated a highly structured network of 3,927 proteins connected by 31,004 interactions, doubling the number of proteins and tripling the number of reliable interactions compared with existing interactome maps
2
. This includes very-low-abundance epigenetic complexes, organellar membrane complexes and non-taggable complexes inferred by abundance correlation. This nearly saturated interactome reveals that the vast majority of yeast proteins are highly connected, with an average of 16 interactors. Similar to social networks between humans, the average shortest distance between proteins is 4.2 interactions. AlphaFold-Multimer provided novel insights into the functional roles of previously uncharacterized proteins in complexes. Our web portal (
www.yeast-interactome.org
) enables extensive exploration of the interactome dataset.
A protein interaction network constructed with data from high-throughput affinity enrichment coupled to mass spectrometry provides a highly saturated yeast interactome with 31,004 interactions, including low-abundance complexes, membrane protein complexes and non-taggable protein complexes.
Journal Article
Material testing and low cycle fatigue life analysis of supercharger gasket
Aiming at the cracking problem of the supercharger metal gasket in the development stage of an engine, an analysis method is established. Firstly, the gasket is assumed to be a spring unit, and transient three-dimensional analysis is carried out to obtain the gap movement of the gasket during the whole cycle process. Then, a detailed two-dimensional model of the gasket is established to calculate the low-cycle fatigue life of the gasket structure through loading temperature and gap movement. The data of tensile strength and elastic modulus at different temperatures were obtained by testing the base material of the gasket. The results indicate that the material performance of the gasket drops sharply when it is higher than 400°C to 500°C, and the temperature of the gasket near the supercharger is in this interval. From the life results, it can be seen that the two layers of the gasket have cracks in half of the test, and the cracking problem can be solved by adjusting the material of the two layers.
Journal Article
A review of current trends in three-dimensional analysis of left ventricular myocardial strain
Three-dimensional (3D) left ventricular (LV) myocardial strain measurements using transthoracic 3D echocardiography speckle tracking analysis have several advantages over two-dimensional (2D) LV strain measurements, because 3D strain values are derived from the entire LV myocardium, yielding more accurate estimates of global and regional LV function. In this review article, we summarize the current status of 3D LV myocardial strain. Specifically, we describe how 3D LV strain analysis is performed. Next, we compare characteristics of 2D and 3D strain, and we explain validation of 3D strain measurements, feasibility and measurement differences between 2D and 3D strain, reference values of 3D strain, and its applications in several clinical scenarios. In some parts of this review, we used a meta-analysis to draw reliable conclusions. We also describe the added value of 3D over 2D strain in several specific pathologies and prognoses. Finally, we discuss novel techniques using 3D strain and suggest its future directions.
Journal Article
Validity and reliability of two-dimensional video-based assessment to measure joint angles during running: A systematic review and meta-analysis
Two-dimensional video analysis systems (2DVAS) are commonly used by clinicians and researchers to determine angles during running. The aim of this systematic review (PROSPERO: CRD42022322798) was to synthesize the literature on the criterion validity and reliability of 2DVAS for measuring angles during running compared to three-dimensional motion analysis systems (3DMAS). We searched for articles on MEDLINE/Pubmed, EMBASE, SciELO, and LILACS up to October/2022. We included studies that evaluated the validity of 2DVAS (when compared to 3DMAS) and/or the reliability of 2DVAS measurements of lower limb and trunk angles during running. Qualitative and quantitative analyses were performed. Seven hundred and five studies were found and 17 were included. Ten studies analysed criterion validity between 2DVAS and 3DMAS and the results ranged from poor to excellent, with most of the parameters assessed presenting poor or moderate validity. Inter-rater reliability of 2DVAS was assessed in nine studies and most of the parameters investigated had good to excellent reliability. Intra-rater reliability (between-day processing) of angular running parameters – investigated in ten studies – was considered excellent for most of the parameters analysed. Inter-session reliability was assessed in three studies and was defined as good or excellent for most of the variables assessed. 2DVAS is a reliable method for measuring joint angles during running. However, the validity of 2DVAS compared to 3DMAS ranges from low to moderate for most running parameters. Therefore, based on the available evidence, caution should be taken when applying 2DVAS, particularly for frontal and transverse plane angles.
Journal Article
Large-amplitude vibrations of cantilevered pipe conveying fluid with arbitrary initial configuration in three-dimensional sense
Up to now, three-dimensional modeling for investigating the nonlinear dynamics of cantilevered pipes conveying fluid with arbitrary initial configurations is still unsolved. This study aims to establish a universal three-dimensional nonlinear dynamic model based on absolute node coordinate formulation (ANCF) and the generalized Lagrange equation. Through this three-dimensional model, static equilibrium configuration and stability analysis for a straight-curved planar pipe system are extensively explored. The results demonstrate that the static equilibrium configuration obtained by the three-dimensional ANCF is limited to the in-plane and hence, it is consistent with that predicted by the two-dimensional model. In terms of stability analysis, two critical flow velocities for flutter instability, namely, the in-plane and out-of-plane critical flow velocities are obtained. It is found that the out-of-plane critical flow velocity is much lower than its counterpart of the in-plane. Regarding on nonlinear dynamics, vibration shapes, time history curves and phase portraits are offered to display rich dynamical behaviors of the pipe system, which are strongly dependent on in-plane and out-of-plane initial conditions. The proposed nonlinear dynamic model in this study can deal with large-amplitude vibrations of pipes conveying fluid with arbitrary initial configurations in the three-dimensional sense, which provides a new thought for the dynamical analysis of nonconservative fluid-conveying pipe system.
Journal Article